Fumarate Hydratase Deficiency Research Articles

#2037 Mitochondrial fumarate promotes ischemia/reperfusion-induced tubular injury

Abstract Background and Aims Mitochondrial dysfunction, a characteristic pathological feature of renal Ischemic/reperfusion injury (I/RI), predisposes tubular epithelial cells to maintain an inflammatory microenvironment, however, the exact mechanisms through which mitochondrial dysfunction modulates the induction of tubular injury remains incompletely understood. Method ESI-QTRAP-MS/MS approach was used to characterize the targeted metabolic profiling of kidney with I/RI. Tubule injury, mitochondrial dysfunction and fumarate level were evaluated using qPCR, transmission electron microscopy, ELISA, and immunohistochemistry. Results We demonstrated that tubule injury occurs at the phase of reperfusion in murine models of I/RI. Meanwhile, the enhanced glycolysis and mitochondrial dysfunction are found to be associated with tubule injury. Further, we found that tubular fumarate, which resulted from fumarate hydratase deficiency and released from dysfunctional mitochondria, promotes tubular injury. Mechanistically, fumarate induces tubular injury through causing disturbance of glutathione (GSH) hemostasis. Suppression of GSH with buthionine sulphoximine administration could deteriorate the fumarate inhibition-mediated tubule injury recovery. Reactive oxygen species/NF-κB signaling activation plays a vital role in fumarate-mediated tubule injury. Conclusion Our studies demonstrated that the mitochondrial-derived fumarate promotes tubular epithelial cells injury in renal I/RI. This finding represents a previously unrecognized mechanism for hypoxia-induced TECs injury. Blockade of fumarate-mediated ROS/NF-κB signaling activation may serve as a novel therapeutic approach to ameliorate hypoxic tubule injury.

Genetic Mechanisms Driving Uterine Leiomyoma Pathobiology, Epidemiology, and Treatment.

Uterine leiomyomas (ULs) are the most common benign tumor of the uterus. They can be associated with symptoms including abnormal uterine bleeding, pelvic pain, urinary frequency, and pregnancy complications. Despite the high prevalence of UL, its underlying pathophysiology mechanisms have historically been poorly understood. Several mechanisms of pathogenesis have been suggested, implicating various genes, growth factors, cytokines, chemokines, and microRNA aberrations. The purpose of this study is to summarize the current research on the relationship of genetics with UL. Specifically, we performed a literature review of published studies to identify how genetic aberrations drive pathophysiology, epidemiology, and therapeutic approaches of UL. With regards to pathophysiology, research has identified MED12 mutations, HMGA2 overexpression, fumarate hydratase deficiency, and cytogenetic abnormalities as contributors to the development of UL. Additionally, epigenetic modifications, such as histone acetylation and DNA methylation, have been identified as contributing to UL tumorigenesis. Specifically, UL stem cells have been found to contain a unique DNA methylation pattern compared to more differentiated UL cells, suggesting that DNA methylation has a role in tumorigenesis. On a population level, genome-wide association studies (GWASs) and epidemiologic analyses have identified 23 genetic loci associated with younger age at menarche and UL growth. Additionally, various GWASs have investigated genetic loci as potential drivers of racial disparities in UL incidence. For example, decreased expression of Cytohesin 4 in African Americans has been associated with increased UL risk. Recent studies have investigated various therapeutic options, including ten-eleven translocation proteins mediating DNA methylation, adenovirus vectors for drug delivery, and "suicide gene therapy" to induce apoptosis. Overall, improved understanding of the genetic and epigenetic drivers of UL on an individual and population level can propel the discovery of novel therapeutic options.

Mitochondrial fumarate promotes ischemia/reperfusion-induced tubular injury.

Mitochondrial dysfunction, a characteristic pathological feature of renal Ischemic/reperfusion injury (I/RI), predisposes tubular epithelial cells to maintain an inflammatory microenvironment, however, the exact mechanisms through which mitochondrial dysfunction modulates the induction of tubular injury remains incompletely understood. ESI-QTRAP-MS/MS approach was used to characterize the targeted metabolic profiling of kidney with I/RI. Tubule injury, mitochondrial dysfunction, and fumarate level were evaluated using qPCR, transmission electron microscopy, ELISA, and immunohistochemistry. We demonstrated that tubule injury occurred at the phase of reperfusion in murine model of I/RI. Meanwhile, enhanced glycolysis and mitochondrial dysfunction were found to be associated with tubule injury. Further, we found that tubular fumarate, which resulted from fumarate hydratase deficiency and released from dysfunctional mitochondria, promoted tubular injury. Mechanistically, fumarate induced tubular injury by causing disturbance of glutathione (GSH) hemostasis. Suppression of GSH with buthionine sulphoximine administration could deteriorate the fumarate inhibition-mediated tubule injury recovery. Reactive oxygen species/NF-κB signaling activation played a vital role in fumarate-mediated tubule injury. Our studies demonstrated that the mitochondrial-derived fumarate promotes tubular epithelial cell injury in renal I/RI. Blockade of fumarate-mediated ROS/NF-κB signaling activation may serve as a novel therapeutic approach to ameliorate hypoxic tubule injury.

The Role of Morphology in Predicting Fumarate Hydratase-deficient Uterine Leiomyomas in Young Women.

Hereditary leiomyomatosis and renal cell carcinoma is caused by germline mutations in the fumarate hydratase (FH) gene and is associated with an increased incidence of leiomyomas and a potentially aggressive variant of renal cell carcinoma. Pathologic evaluation of uterine leiomyoma can provide an opportunity for early recognition of the syndrome. We reviewed all archived slides of the cases to identify the characteristic morphologic features described for FH-deficient leiomyomas. We performed immunohistochemistry on whole sections of patients with uterine leiomyoma to evaluate for both FH and 2-succinocysteine (2SC) expression. Of the 106 cases, 19 showed the characteristic eosinophilic nucleoli with perinuclear halos, and 24 revealed a characteristic eosinophilic cytoplasmic inclusion consisting of pink globules present within the cytoplasm. Both of these morphologic findings were present together in 15 cases, and hemangiopericytomatous vessels were detected in 23 cases. The loss of FH protein expression was detected in 14 out of 106 cases (13%), and 13 out of 106 cases (12%) were positive for 2SC. We detected 10 cases with both 2SC-positive and FH expression loss. The presence of eosinophilic nucleoli with perinuclear halos and eosinophilic cytoplasmic inclusion was associated with both loss of FH protein expression and 2SC positivity ( P < 0.001). These findings underscore the importance of hematoxylin and eosin-based predictive morphology in FH-deficient uterine leiomyomas. Therefore, morphologic assessment of uterine leiomyomas for features of FH deficiency can serve as a screening tool for hereditary leiomyomatosis and renal cell carcinoma syndrome, allowing patients to be divided according to their hereditary risk assessment.

Comprehensive isotopomer analysis of glutamate and aspartate in small tissue samples

Stable isotopes are powerful tools to assess metabolism. 13C labeling is detected using nuclear magnetic resonance (NMR) spectroscopy or mass spectrometry (MS). MS has excellent sensitivity but generally cannot discriminate among different 13C positions (isotopomers), whereas NMR is less sensitive but reports some isotopomers. Here, we develop an MS method that reports all 16 aspartate and 32 glutamate isotopomers while requiring less than 1% of the sample used for NMR. This method discriminates between pathways that result in the same number of 13C labels in aspartate and glutamate, providing enhanced specificity over conventional MS. We demonstrate regional metabolic heterogeneity within human tumors, document the impact of fumarate hydratase (FH) deficiency in human renal cancers, and investigate the contributions of tricarboxylic acid (TCA) cycle turnover and CO2 recycling to isotope labeling invivo. This method can accompany NMR or standard MS to provide outstanding sensitivity in isotope-labeling experiments, particularly invivo.

A novel nonsense mutation in the fumarate hydratase gene in a Chinese patient with recurrent leiomyomas

To describe a novel nonsense mutation in the fumarate hydratase (FH) gene in a Chinese patient with recurrent multiple leiomyomas. Case report. Medical school-affiliated tertiary hospital. A nulligravida patient aged 30 years with large uterine leiomyomas (ULMs) and severe anemia. Clinical evaluation, abdominal myomectomy, targeted next-generation sequencing. Fumarate hydratase gene mutation in ULMs. A novel nonsense mutation (c.771T>G) in the FH gene was identified in this patient. This mutation is located in exon 6, which encodes the N-terminal fumarate lyase domain. It leads to a predicted truncated protein with loss of the majority of the lyase domain, resulting in FH deficiency. Because of the recurrent multiple leiomyomas, this patient received 2 myomectomies within 5 years. On immunostaining the leiomyoma, FH deficiency was detected, and targeted next-generation sequencing revealed a novel mutation of the FH gene. This patient was at risk for early disease relapse and developing renal cancer, and close disease monitoring is recommended. Meanwhile, the expanded mutation database should benefit patients in diagnosing FH gene-associated ULMs.

Fumarate Hydratase and S-(2-Succinyl)-Cysteine Immunohistochemistry Shows Evidence of Fumarate Hydratase Deficiency in 2% of Uterine Leiomyosarcomas: A Cohort Study of 348 Tumors.

Approximately 1% to 1.5% of uterine leiomyomas are fumarate hydratase (FH)-deficient (FHd). A subset of these are associated with germline FH mutations. However, the prevalence and clinicopathologic characteristics of FHd uterine leiomyosarcoma (uLMS) remain unknown. Clinicopathologic data were collected for 348 uLMS. Morphologic features associated with FH deficiency (staghorn-type vessels, alveolar-pattern edema, macronucleoli with perinucleolar clearing, eosinophilic cytoplasmic inclusions, and chain-like nuclear arrangement) were documented. All 348 tumors were studied by FH immunohistochemistry. Eighty-nine were also studied by S-(2-succinyl)-cysteine (2SC) immunohistochemistry. Seven (2%) FHd uLMS were identified. Five showed uniformly negative FH and diffusely positive 2SC immunostaining; 1 showed variably negative to weak to strong FH and diffusely positive 2SC immunostaining; and 1 showed retained FH staining alongside positive 2SC confined to a morphologically distinct subclone. Three of 7 patients had extrauterine disease at presentation, and 3 of 6 had persistent disease or died from disease. Macronucleoli with perinucleolar clearing were significantly more common in FHd uLMS (7/7) than in uLMS with retained FH (182/341; P =0.017). Disease-specific survival, disease-free survival, and other morphologic features of FH deficiency did not differ significantly between FHd and FH-retained tumors. Our data emphasize that immunohistochemical FH deficiency does not preclude malignancy in uterine smooth muscle tumors. However, the biological significance and molecular basis of FH deficiency in uLMS, including any relationship to germline FH mutation, remain unknown, and a larger multi-institutional effort is necessary to gather sufficient FHd uLMS for more robustly powered clinicopathologic and for molecular characterization.

A Clinicopathologic and Molecular Analysis of Fumarate Hydratase-deficient Pheochromocytoma and Paraganglioma.

Up to 40% of pheochromocytomas (PCCs) and paragangliomas (PGLs) are hereditary. Germline mutations/deletions in fumarate hydratase ( FH ) cause hereditary leiomyomatosis and renal cell carcinoma syndrome which manifests predominantly with FH-deficient uterine/cutaneous leiomyomas and renal cell carcinomas (RCCs)-tumors characterized by loss of immunohistochemical (IHC) expression of FH and/or positive staining for S-(2-succino)-cysteine. Occasional patients develop PCC/PGL. We investigated the incidence, morphologic, and clinical features of FH-deficient PCC/PGL. We identified 589 patients with PCC/PGLs that underwent IHC screening for FH and/or S-(2-succino)-cysteine. Eight (1.4%) PCC/PGLs were FH deficient (1.1% in an unselected population). The median age for FH-deficient cases was 55 (range: 30 to 77y) with 50% arising in the adrenal. All 4 with biochemical data were noradrenergic. Two (25%) metastasized, 1 dying of disease after 174 months. Germline testing was performed on 7 patients, 6 of whom had FH missense mutations. None were known to have a significant family history before presentation or developed cutaneous leiomyomas, or FH-deficient RCC at extended follow-up. The patient wild-type for FH on germline testing was demonstrated to have somatic FH mutation and loss of heterozygosity corresponding to areas of subclonal FH deficiency in her tumor. One patient did not undergo germline testing, but FH mutation was demonstrated in his tumor. We conclude that FH-deficient PCC/PGL are underrecognized but can be identified by IHC. FH-deficient PCC/PGL are strongly associated with germline missense mutations but are infrequently associated with leiomyoma or RCC, suggesting there may be a genotype-phenotype correlation. FH-deficient PCC/PGL may have a higher metastatic risk.

MR Spectroscopy for Detecting Fumarate Hydratase Deficiency in Hereditary Leiomyomatosis and Renal Cell Carcinoma Syndrome.

Background Noninvasive in vivo detection of fumarate accumulation may help identify fumarate hydratase deficiency in renal cancer related to hereditary leiomyomatosis and renal cell carcinoma (HLRCC) syndrome. Purpose To investigate the feasibility of MR spectroscopy (MRS) in detecting elevated fumarate levels in HLRCC-associated renal cancers. Materials and Methods This study included an experimental xenograft mouse model and prospective clinical cohort. First, MRS was performed on patient-derived tumor xenograft models and control models to detect fumarate. Then, consecutive participants with clinical suspicion of HLRCC-associated renal tumors were enrolled. For the detection of fumarate, MRS results were classified as detected, borderline, undetected, or technical failure. The sensitivity, specificity, and accuracy of MRS for diagnosing HLRCC-associated renal cancer were assessed. The signal-to-noise ratio (SNR) of the fumarate peak was calculated and evaluated with receiver operating characteristic curve analysis. Results Fumarate peaks were detected at 6.54 parts per million in all three patient-derived xenograft models. A total of 38 participants (21 men; mean age, 47 years [range, 18-71 years]) with 46 lesions were analyzed. All primary HLRCC-associated renal cancers showed a fumarate peak; among the seven metastatic HLRCC-associated lesions, a fumarate peak was detected in three lesions and borderline in two. When only detected peaks were regarded as positive findings, the sensitivity, specificity, and accuracy of MRS at the lesion level were 69% (nine of 13 lesions), 100% (33 of 33 lesions), and 91% (42 of 46 lesions), respectively. When borderline peaks were also included as a positive finding, the sensitivity, specificity, and accuracy reached 85% (11 of 13 lesions), 88% (29 of 33 lesions), and 87% (40 of 46 lesions), respectively. The SNR of fumarate showed an area under the receiver operating characteristic curve of 0.87 for classifying HLRCC-associated tumors. Conclusion MR spectroscopy of fumarate was sensitive and specific for hereditary leiomyomatosis and renal cell carcinoma-associated tumors. © RSNA, 2022 Online supplemental material is available for this article.

Targeting strategies in the treatment of fumarate hydratase deficient renal cell carcinoma.

Fumarate hydratase (FH) - deficient renal cell carcinoma (FHdRCC) is a rare aggressive subtype of RCC caused by a germline or sporadic loss-of-function mutation in the FH gene. Here, we summarize how FH deficiency results in the accumulation of fumarate, which in turn leads to activation of hypoxia-inducible factor (HIF) through inhibition of prolyl hydroxylases. HIF promotes tumorigenesis by orchestrating a metabolic switch to glycolysis even under normoxia, a phenomenon well-known as the Warburg effect. HIF activates the transcription of many genes, including vascular endothelial growth factor (VEGF). Crosstalk between HIF and epidermal growth factor receptor (EGFR) has also been described as a tumor-promoting mechanism. In this review we discuss therapeutic options for FHdRCC with a focus on anti-angiogenesis and EGFR-blockade. We also address potential targets that arise within the metabolic escape routes taken by FH-deficient cells for cell growth and survival.

Multicenter retrospective study of 38 cases with fumarate hydratase deficiency uterine leiomyoma

Objective: To investigate the clinicopathological features of fumarate hydratase (FH) deficiency uterine leiomyoma. Methods: The data of 38 patients with FH deficiency uterine leiomyoma were screened and analyzed. The expressions of FH, S-(2-succino)-cysteine (2SC), desmin, p16, p53, CD10 and cell proliferation associated nuclear antigen (Ki-67) proteins were detected by immunohistochemistry, and their clinicopathological features were analyzed retrospectively. Results: (1) Clinical features: the median age of the patients was (42.5±7.4) years old. Twenty-one cases (55%) of them were myomas found in physical examination, and the median maximum diameter of the tumor was 6.0 cm (range: 5.0-7.5 cm); myomectomy was performed in 23 cases (61%), total hysterectomy with or without bilateral appendages in 15 cases (39%); laparoscopic surgery in 27 cases (71%), open surgery in 11 cases (29%); none of the patients had renal cell carcinoma. (2) Histological features: atypical nuclear cells were distributed locally or diffusely, eosinophilic nucleoli and intranuclear inclusion bodies could be seen, glass like globules could be seen in the cytoplasm, nuclear division was 0-4/10 high power field (HPF), and antler like blood vessels and pulmonary edema-like changes could be seen in the stroma. Among 38 patients with FH deficiency uterine leiomyoma, FH was negative in 37 cases (97%), and positive in 1 case (3%); 2SC, desmin, p16, p53, CD10 and Ki-67 showed focal positive expression in 38 cases (100%), including 35 cases (92%) with Ki-67 index<10% and 3 cases (8%) with Ki-67 index ≥10%. (3) Follow-up: 4 cases (11%) recurred, and there was no death. There were significant differences in age, family history, distribution of atypical nuclei and mitosis number between recurrent group and non-recurrent group (all P<0.05). Conclusions: FH deficiency uterine leiomyoma is a rare tumor, which needs pathological examination,immunohistochemical examination and clinical history. Patients younger than 43 years old, with family history, histologically atypical diffuse nuclear distribution and mitotic number ≥3/10 HPF should be alert to the risk of recurrence.

Clinicopathological and molecular characteristics of fumarate hydratase–deficient uterine smooth muscle tumors: a single-center study of 52 cases

The fumarate hydratase (FH) gene germline mutations cause hereditary leiomyomatosis and renal cell carcinoma syndrome (HLRCC), predisposing carriers to uterine and cutaneous leiomyomas and renal cell carcinoma. In this study, we aim to investigate morphology and the correlation between FH mutation in FH-deficient (FH-d) uterine smooth muscle tumors (uSMTs). We conducted immunohistochemical staining in 161 cases of uSMTs to detect FH deficiency. We identified 52 cases (52/161, 32%)of FH-d, including 34 leiomyomas with bizarre nuclei, 10 uSMTs of uncertain malignant potential (STUMPs), 4 cellular leiomyomas, 3 usual type leiomyomas, and 1 leiomyosarcoma. Patients with FH-d were aged 24-67 years (median, 40 years). The most common FH-d morphological features included staghorn-shaped blood vessels (87%), bizarre nuclei (81%), alveolar pattern edema (65%), macronucleoli surrounded by a halo (65%), cytoplasmic eosinophilic globules (56%), and chain-like distribution of smooth muscle cells (52%). A targeted next-generation sequence was performed in 11 of 52 FH-d tumors. Five cases (5/11, 45%) were found with FH germline mutations, including 4 leiomyomas with bizarre nuclei and 1 STUMP. The median age of patients with germline FH mutation was 30 years. The germline mutations included 3 pathogenic, 1 likely pathogenic, and 1 rare uncertain clinical significance variants. Our results revealed that FH-d uSMTs usually exhibit the distinct morphology features and high frequency of FH germline mutations. The combination of predictive morphology evaluation, FH immunotype, and molecular testing is helpful for the screening of HLRCC in uSMTs.

Different Fumarate Hydratase Gene Variants Are Associated With Distinct Cancer Phenotypes.

Whether individuals with monoallelic FH pathogenic variants (PVs) associated with autosomal recessive fumarate hydratase (FH) deficiency are also at risk of autosomal dominant FH-associated tumors is of paramount clinical importance. A retrospective study of individuals with a PV in the FH gene identified via multigene panel testing from 2012 to 2019 through a single testing laboratory was performed. Cancer histories of individuals with PVs in FH (FH PV) were compared to those with PVs associated only with autosomal recessive FH deficiency (FH-d PV) and to FH-negative controls. Cancer histories of individuals with truncating versus nontruncating FH PV were also compared. Individuals with FH PV were more likely to have kidney cancer than those with FH-d PV (odds ratio, 9.0; 95% CI, 4.4 to 20.0; P < .001) or FH-negative controls (odds ratio, 7.6; 95% CI, 5.2 to 11.2; P value < .001). The FH PV cohort had kidney cancer at a significantly younger age (median age: 35.0 years; interquartile range, 26.0-45.0 years) than the FH-d PV cohort (median age: 44.5 years; interquartile range, 43.5-53.5 years; P = .011). Within the FH PV cohort, there were no differences in the frequency or age at kidney cancer between those with truncating versus nontruncating PV. Unlike FH PV, FH-d PV are not associated with kidney cancers at early ages of onset. The FH-d PV cohort had a cancer phenotype that resembled FH-negative controls. These data may inform genetic counseling and risk assessment of individuals with FH-d PV.

The Gynecologist's Role in the Workup and Management of Patients with Leiomyomas Demonstrating Fumarate Hydratase Deficiency

Study Objective Fumarate hydratase (FH) tumor predisposition syndrome or hereditary leiomyomatosis renal cell cancer (HLRCC) is caused by an autosomal-dominant heterozygous mutation in the FH gene. It is characterized by uterine or cutaneous leiomyomas and renal tumors. Timely diagnosis of HLRCC allows for cancer surveillance. Yet, delays in diagnosis are common in patients with isolated uterine findings. Given that leiomyomas are the most common benign tumors in reproductive-aged women, gynecologists are in an opportunistic position to detect HLRCC earlier. In this series, we present three patients with FH-deficient leiomyomas, and review the gynecologist's unique role in screening, workup, and diagnosis of HLRCC. Design Case Series. Setting Academic institution. Patients or Participants Three patients. Interventions Surgery and genetic screening. Measurements and Main Results Case 1 A 33-year-old with heavy menstrual bleeding and an 18cm uterine lesion presents for abdominal myomectomy. Pathological evaluation was suggestive of FH-deficient leiomyoma, which was confirmed by immunohistochemistry (IHC). She was lost to follow up. Case 2 A 32-year-old with pelvic pain, infertility, and a submucosal fibroid presents for robotic myomectomy. Pathology and IHC confirmed a diagnosis of FH-deficient leiomyoma. Genetic testing for FH mutation was negative. Case 3 A 52-year-old with adenomyosis unresponsive to conservative management presents for hysterectomy. Pathological evaluation was suggestive of FH-deficient leiomyoma, however IHC did not support this diagnosis. Genetic testing was negative. Conclusion HLRCC presents with a variation of phenotypes ranging from leiomyomas to metastatic renal cell carcinoma. Our cases underscore the gynecologist's unique role in the diagnosis of HLRCC. The majority of uterine fibroids are not associated with an increased risk malignancy. FH-deficient leiomyomas can occur in both syndromic and sporadic settings. A thorough history can identify patients at risk. Characteristic histopathological features should prompt genetic evaluation. Management requires a multidisciplinary approach and surveillance can be offered to individuals with even a suspected diagnosis in whom an FH mutation has not been identified. Fumarate hydratase (FH) tumor predisposition syndrome or hereditary leiomyomatosis renal cell cancer (HLRCC) is caused by an autosomal-dominant heterozygous mutation in the FH gene. It is characterized by uterine or cutaneous leiomyomas and renal tumors. Timely diagnosis of HLRCC allows for cancer surveillance. Yet, delays in diagnosis are common in patients with isolated uterine findings. Given that leiomyomas are the most common benign tumors in reproductive-aged women, gynecologists are in an opportunistic position to detect HLRCC earlier. In this series, we present three patients with FH-deficient leiomyomas, and review the gynecologist's unique role in screening, workup, and diagnosis of HLRCC. Case Series. Academic institution. Three patients. Surgery and genetic screening. Case 1 A 33-year-old with heavy menstrual bleeding and an 18cm uterine lesion presents for abdominal myomectomy. Pathological evaluation was suggestive of FH-deficient leiomyoma, which was confirmed by immunohistochemistry (IHC). She was lost to follow up. Case 2 A 32-year-old with pelvic pain, infertility, and a submucosal fibroid presents for robotic myomectomy. Pathology and IHC confirmed a diagnosis of FH-deficient leiomyoma. Genetic testing for FH mutation was negative. Case 3 A 52-year-old with adenomyosis unresponsive to conservative management presents for hysterectomy. Pathological evaluation was suggestive of FH-deficient leiomyoma, however IHC did not support this diagnosis. Genetic testing was negative. HLRCC presents with a variation of phenotypes ranging from leiomyomas to metastatic renal cell carcinoma. Our cases underscore the gynecologist's unique role in the diagnosis of HLRCC. The majority of uterine fibroids are not associated with an increased risk malignancy. FH-deficient leiomyomas can occur in both syndromic and sporadic settings. A thorough history can identify patients at risk. Characteristic histopathological features should prompt genetic evaluation. Management requires a multidisciplinary approach and surveillance can be offered to individuals with even a suspected diagnosis in whom an FH mutation has not been identified.

Urine Organic Acid Analysis: Key Diagnostic Test for Fumaric Aciduria in a Sri Lankan Child.

Fumaric aciduria resulting from fumarate hydratase deficiency is a rare inherited disorder of the Krebs tricarboxylic acid cycle that is characterized by neurologic manifestations, a spectrum of brain abnormalities, and the excretion of fumaric acid in urine. We describe a 3 year old Sri Lankan boy who was referred at age 10 months with poor weight gain and hypotonia for further laboratory investigations. In addition to global developmental delay, there were noticeable dysmorphic features with a prominent forehead, low-set ears, micrognathia, and hypertelorism with persistent neutropenia. Urine organic acid assay revealed a massive elevation of fumaric acid on 2 occasions. Molecular analysis revealed a homozygous likely pathogenic missense variant, NM000143.3:c.1048C>T p. (Arg350Trp), in the FH gene, confirming the biochemical diagnosis. Our patient was the first patient in Sri Lanka molecularly diagnosed with fumaric aciduria. This case study highlights the importance of performing organic acid assays in children presenting with neurologic manifestations especially when these are suspected to have a metabolic basis.

Fumarate Hydratase Deficiency Should be Considered in the Differential Diagnosis of Uterine and Extrauterine Smooth Muscle Tumors of Uncertain Malignant Potential (STUMP).

Fumarate hydratase-deficient leiomyomas (dFH leiomyomas) often display atypical pathologic features yet exhibit a benign clinical course. Recent data suggest that dFH leiomyomas may be misclassified as smooth muscle tumors of uncertain malignant potential, a category that encompasses a heterogenous subgroup of uterine neoplasms with smooth muscle differentiation and atypical features that impart ambiguity regarding their expected clinical behavior. dFH leiomyomas can be seen in the context of hereditary leiomyomatosis and renal cell carcinoma syndrome or in the sporadic setting. In this retrospective study, we sought to examine the prevalence and clinicopathologic characteristics of dFH leiomyomas in 48 tumors previously diagnosed as smooth muscle tumors of uncertain malignant potential from 38 patients. Of these 48 tumors, 3 (6.3%) occurring in 2 patients were found to be deficient for FH by immunohistochemistry, including 1 uterine and 2 extrauterine (abdominopelvic) tumors. The 3 tumors showed histologic features typical of dFH leiomyomas, including hemangiopericytoma-like vessels, edema, macronucleoli, and atypia. Neither patient developed recurrent leiomyomas or renal cell carcinoma, and both were alive without disease at last follow-up. Our data suggest that dFH leiomyomas should be considered in the differential diagnosis of smooth muscle tumors of uncertain malignant potential, even in the context of extrauterine disease. Identification of FH deficiency in these tumors supports their classification as dFH leiomyomas despite their atypical morphologic features and/or clinical presentation. Importantly, detection of dFH in these cases may identify women at increased risk for hereditary leiomyomatosis and renal cell carcinoma who would benefit from genetic counseling and consideration for FH germline testing.

Biochemical Analysis of a Patient with Fumarate Hydratase Deficiency

Mutations in the human FH gene are associated with the rare recessive metabolic disease known as Fumarate Hydratase Deficiency (FHD). Symptoms associated with FHD include brain malformations, developmental delays, poor growth, and seizures. Many FHD patients do not survive past early childhood. The FH gene encodes the Krebs cycle enzyme fumarate hydratase, also known as fumarase. We describe the symptoms and treatment of a female adolescent with FHD, along with a biochemical analysis of the patient's fumarase variants. While FHD patients commonly experience infantile spasms, the patient had epileptic spasms that occurred only later in childhood. After several first line medication trials failed, the patient responded well to lacosamide for her seizures. We biochemically analyzed the patient's two fumarase variants, introducing each of the mutations (D65G and E432Kfs*17) into a recombinant plasmid containing the human FH gene. We purified and characterized wild-type fumarase along with the variants. E432Kfs*17 had defects in oligomerization and catalysis, including a ~1500-fold decrease in turnover (kcat). The variant D65G displayed oligomerization and turnover similar to wild-type, and only a very mild defect in Km. We hypothesize that the rather mild deficiency of the D65G variant may have contributed to the mild clinical severity of the patient.

Genotypic and Phenotypic Characteristics of Hereditary Leiomyomatosis and Renal Cell Cancer Syndrome in Korean Patients.

BackgroundHereditary leiomyomatosis and renal cell cancer (HLRCC) is an autosomal dominant cancer predisposition syndrome. HLRCC is characterized by the development of cutaneous leiomyomas, early-onset uterine leiomyomas, and HLRCC-associated renal cell cancer (RCC) and caused by germline fumarate hydratase (FH) deficiency. We investigated the genotypic and phenotypic characteristics of Korean patients with HLRCC.MethodsWe performed direct sequencing analysis of FH in 13 patients with suspected HLRCC and their family members. A chromosomal microarray test was performed in female patients with negative sequencing results but highly suspected HLRCC. In addition, we analyzed the clinical characteristics and evaluated the genotype–phenotype correlations in Korean patients with HLRCC.ResultsWe identified six different pathogenic or likely pathogenic FH variants in six of the 13 patients (46.2%). The variants included two nonsense variants, two splicing variants, one frameshift variant, and one missense variant. Of the six variants, two (33.3%) were novel (c.132+1G > C, and c.243dup). RCC and early-onset uterine leiomyoma were frequently observed in families with HLRCC, while cutaneous leiomyoma was less common. No significant genotype–phenotype correlation was observed.ConclusionsWe describe the genotypic and phenotypic spectrum in a small series of Korean patients with HLRCC. Our data reveal the unique characteristics of Korean patients with HLRCC and suggest a need for establishing an optimal diagnostic approach for them.

Hereditary leiomyomatosis and renal cell carcinoma syndrome associated uterine smooth muscle tumors: Bridging morphology and clinical screening.

Hereditary leiomyomatosis and renal cell carcinoma (HLRCC) is an autosomal dominant familial syndrome that results from germline mutation in the fumarate hydratase (FH) gene and is associated with an increased risk for smooth muscle tumors of the uterus and skin and renal cell carcinoma. HLRCC associated RCC develop in up to 25% of patients, often presenting in the fourth decade and are high stage, aggressive tumors with poor clinical outcome. Most women with HLRCC develop large and bulky uterine smooth muscle tumors (USMT) in the second to third decade, thus presenting the ideal opportunity for early detection of HLCC to enable timely implementation of surveillance for their RCC risk. However, the concept of screening women with USMT for HLRCC is challenging given that HLRCC is rare but USMT are common. In addition, FH deficiency in USMT can also result from sporadic FH gene aberrations, unrelated to HLRCC, further complicating any potential screening process. Recent studies show that tumor morphology can be used to identify FH deficiency in USMT and thereby direct patients to formal genetic counseling. The low magnification clues of staghorn shaped blood vessels and alveolar pattern should prompt for high magnification examination for eosinophilic cytoplasmic inclusions and oval nuclei containing prominent eosinophilic macronucleoli surrounded by a halo. Additional clues include Schwannoma-like growth and chain-like distribution of the tumor cells. Although immunostains exist for FH and 2SC, their role is limited in the presence of well-developed FH deficient morphology. The prevalence of germline pathogenic mutation in FH among women with USMT with FH deficient morphology is as high as 50% in some studies, with somatic FH mutation accounting for the remainder. Therefore, morphologic evaluation of USMT for features of FH deficiency can serve as a screening tool for HLRCC syndrome by triaging patients to formal hereditary risk assessment.

Targeted sequencing of FH-deficient uterine leiomyomas reveals biallelic inactivating somatic fumarase variants and allows characterization of missense variants

Uterine leiomyomas (ULs) constitute a considerable health burden in the general female population. The fumarate hydratase (FH) deficient subtype is found in up to 1.6% and can occur in hereditary leiomyomatosis and renal cell carcinoma (HLRCC) syndrome. We sequenced 13 FH deficient ULs from a previous immunohistochemical screen using a targeted panel and identified biallelic FH variants in all. In eight, we found an FH point mutation (two truncating, six missense) with evidence for loss of the second allele. Variant allele-frequencies in all cases with a point mutation pointed to somatic variants. Spatial clustering of the identified missense variants in the lyase domain indicated altered fumarase oligomerization with subsequent degradation as explanation for the observed FH deficiency. Biallelic FH deletions in five tumors confirm the importance of copy number loss as mutational mechanism. By curating all pathogenic FH variants and calculating their population frequency, we estimate a carrier frequency of up to 1/2,563. Comparing with the prevalence of FH deficient ULs, we conclude that most are sporadic and estimate 2.7–13.9% of females with an FH deficient UL to carry a germline FH variant. Further prospective tumor/normal sequencing studies are needed to develop a reliable screening strategy for HLRCC in women with ULs.