Heterozygous Variants Research Articles

Prenatal detection of novel compound heterozygous variants of the PLD1 gene in a fetus with congenital heart disease

Prenatal detection of novel compound heterozygous variants of the PLD1 gene in a fetus with congenital heart disease

Compound heterozygous variants in the ABCG5 gene in a Korean boy with sitosterolemia.

Compound heterozygous variants in the ABCG5 gene in a Korean boy with sitosterolemia.

Persistent renal dysfunction post-chemotherapy: a diagnostic conundrum in pediatric cancer survivorship – a case report

BackgroundLate-onset type II Bartter syndrome is an exceedingly rare condition, with only six documented cases presenting symptoms and signs beyond infancy. We report a unique case of late-onset type II Bartter syndrome with an atypical presentation and clinical course following chemotherapy treatment during childhood.Case presentationA 10-year-old boy, diagnosed with hepatoblastoma at age 2 and treated with cisplatin and epirubicin, presented with polyuria, polydipsia, failure to thrive, and electrolyte imbalances. He exhibited hypokalemia, metabolic alkalosis, and elevated urinary excretion of sodium, chloride, calcium, and magnesium. Whole exome sequencing and Sanger sequencing identified compound heterozygous variants in the KCNJ1 gene, confirming the diagnosis of type II Bartter syndrome. The patient’s clinical presentation was distinct from previously reported cases, with an absence of nephrocalcinosis, unusually small and hyperechoic kidneys, and a substantial decline in kidney function. Treatment included oral potassium supplementation, spironolactone, and angiotensin-converting enzyme inhibitors.ConclusionsThis case highlights the importance of considering late-onset Bartter syndrome in patients with a history of chemotherapy presenting with persistent electrolyte imbalances and ongoing renal dysfunction. The atypical features and rapid progression of chronic kidney disease in this patient may be attributed to the deleterious nature of the identified variants and the potential impact of previous chemotherapy on kidney susceptibility to damage. Careful monitoring and management of electrolyte imbalances and renal function are crucial in such cases.

A New Case of Mitochondrial RNA Helicase SUPV3L1-Associated Neurodegenerative Disease: Ataxia, Spasticity, Optic Atrophy, and Skin Hypopigmentation (ASOASH)

Background: The SUPV3L1 gene encodes ATP-dependent RNA helicase SUPV3L1, which is a part of the mitochondrial degradosome complex or SUV3. SUPV3L1 unwinds secondary structures of mitochondrial RNA (mtRNA) and facilitates the degradation of mtRNA molecules. A nonsense homozygous variant in the SUPV3L1 gene was recently associated with mitochondrial disease. Our study presents the second documented case of SUPV3L1 pathology in humans. Methods: Whole-genome sequencing was performed on the NovaSeq 6000 platform using pair-end reading. Data analysis was performed with an in-house developed pipeline. Results: The 17-year-old female patient exhibited a diverse array of symptoms, including ataxia, spastic paraparesis, cognitive deficit, optic atrophy, and horizontal gaze-evoked nystagmus. Early onset of symptoms, such as ataxic gait and nystagmus, was noted, with subsequent progression of neurological manifestations. At the time of the observation, the proband had extensive regions of hypopigmented skin patches on the body and extremities, which have progressed over time. Whole-genome sequencing revealed compound heterozygous variants in the SUPV3L1 gene: c.272-2A>G and c.1924A>C; p.(Ser642Arg). RNA analysis demonstrated splicing changes attributable to the c.272-2A>G variant. ELISA assay showed increased Complex I content in the patient’s fibroblasts. This case underscores the phenotypic diversity associated with SUPV3L1 mutations, emphasizing the importance of considering mitochondrial RNA helicase dysfunction in the differential diagnosis of neurodegenerative disorders. Further elucidation of the molecular mechanisms underlying SUPV3L1-associated pathology may provide valuable insights into targeted therapeutic interventions.

Epilepsy in Loeys-Dietz Syndrome: The Rare Concurrence of a Connective Tissue and Neuronal Migration Disorder

We present a 7-year-old girl who presented to our emergency department in active status epilepticus. Seizures responded to standard antiepileptic medications; however, baseline work-up for seizure etiology remained unremarkable. Her new-onset seizures were further investigated via EEG and MRI brain, which revealed focal epileptiform discharges and periventricular nodular heterotopia, respectively. Concurrently, the clinical evaluation revealed extensive marfanoid features, and a personal history of eczema and asthma. Her family history was pertinent for aortic valve disease, asthma, and tall stature. Given the peculiar skeletal features, allergic propensities and coexistent weighty family history, a molecular genetic panel analysis for Marfan Syndrome and Loeys-Dietz Syndrome (LDS) were sought. Genetic testing revealed an underlying heterozygous variant in the TGFBR-1 gene; thereby confirming the presence of LDS. The child had responded well to single antiepileptic agent therapy and was discharged in good condition with regular outpatient cardiac and neurology follow-up. This is a unique case reported of a child with genetically diagnosed LDS concurring with an underlying neuronal migration disorder, manifesting in an acute, severe, and lifethreatening fashion.

Novel FLNC variants in pediatric cardiomyopathy: an insight into disease mechanisms

BackgroundFLNC gene variants have predominantly been reported in adult populations with cardiomyopathies, and early-onset cases are less common. The genotype–phenotype relationship indicates that dilated cardiomyopathy (DCM) is often associated with FLNC truncating variants.MethodsWe conducted a comprehensive genetic analysis using next generation sequencing (NGS) to identify FLNC variants in patients with cardiovascular conditions. Detailed phenotypic and variant analyses were performed to characterize the clinical features and genetic alterations. Minigene assays and structural modeling were used to investigate the pathogenicity caused by the identified variants.ResultsIn a cohort of 58 patients, novel heterozygous FLNC variants, c.3962A > T (p.Glu1321Val) and c.7543C > T (p.Leu2515Phe), were identified in patients presenting with dilated and mixed restrictive/hypertrophic cardiomyopathies, respectively. The c.3962A > T variant disrupted normal splicing, as demonstrated through the splicing prediction tool and minigene studies, further emphasizing its pathogenic potential.ConclusionFor missense variants of FLNC in patients with DCM, the splicing effect of the variant should be carefully checked. Early detection and intervention are crucial given the high risk of sudden cardiac death and severe cardiac complications.

Carrier frequency and incidence estimation of deficiency of adenosine deaminase 2 in the Chinese population based on massive exome sequencing data

Deficiency of adenosine deaminase 2 (DADA2) is an autosomal recessive autoinflammatory disease characterised by early onset stroke, recurrent fever, and diverse vascular pathologies, caused by loss-of-function homozygous or compound heterozygous variants of ADA2. This research aimed to determine the carrier frequency and expected incidence of DADA2 in China, using massive exome sequencing (ES) data. A total of 50 likely pathogenic/pathogenic variants (LP/PVs) were identified among 69,413 Chinese individuals, including 20 novel and rare variants (<0.0022 % allele frequency), expanding the known spectrum of PVs in ADA2. The overall carrier frequency in the Chinese population was 1.05 % (732/69,413) and the estimated incidence of DADA2 was approximately one in 92,251 individuals. The present study provides an accurate estimation of the prevalence of DADA2 in China, supporting genetic counseling, early diagnosis treatment, and prognostic evaluation.

Thiamine-Responsive Megaloblastic Anemia (TRMA) Syndrome mimicking myelodysplastic neoplasm (MDS)

Thiamine-responsive megaloblastic anemia syndrome (TRMA) is a rare autosomal recessive disease with a homozygous or compound-heterozygous mutation in the SLC19A2 gene characterized by megaloblastic anemia, diabetes mellitus (DM), and sensorineural hearing-loss with onset in childhood. Folic acid and vitamin B12 in serum are normal with dysplastic erythropoiesis in the bone marrow often mimicking myelodysplastic neoplasms (MDN) as a potential differential diagnosis. Thiamine substitution leads to normalization of anemia, without effects on hearing-loss or DM. We report about a 38-year-old male patient, presented with a 12-year history of anemia, insulin dependent DM, optic neuropathy and a cataract since early childhood. The laboratory showed megaloblastic anemia. Other values were normal. The bone marrow smear showed dysplastic erythropoiesis with megaloblastic changes, and normal findings in cytogenetic and molecular genetic examinations. Next-generation sequencing based diagnostics revealed a heterozygous missense variant in the SLC19A2 gene on the maternal allele and a 3.4 Mb inversion in the chromosomal region 1q24.2 with breaking points in FAM78B and SLC19A2 on the paternal allele. Treatment with oral thiamine 100 mg daily was initiated, and 12 weeks later Hb levels and bone marrow morphology had normalized. Late-onset TRMA should be considered in adult patients with indicative comorbidities and a typical phenotype, which may mimic features of MDS.

Amplicon-based long-read sequencing is useful for confirming zygosity of DSG2 variants associated with Japanese ARVC

Abstract Background Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited cardiomyopathy mainly caused by desmosomal gene variants. Previously, we reported that DSG2 variants were the most common in 153 Japanese ARVC probands (DSG2 multiple, n=62 and single, n=4; PKP2, n=28; others, n=7). Among the multiple DSG2 variant carriers, 22 probands were compound heterozygous carriers, and 25 were homozygous, which were confirmed by genetic testing for family members (Figure A). On the other hand, 88% of their family members with single DSG2 variant carriers were not diagnosed with ARVC, which meant that recessive DSG2 variants were the major cause of ARVC in Japan. However, zygosities in remaining 15 probands with multiple DSG2 variants were unknown due to the lack of genome data from their parents. Purpose This study aimed to clarify the zygosities of multiple DSG2 variants using amplicon-based long-read sequencing. Methods Genomic DNA was extracted from whole blood using standard protocols. The range containing multiple variants was amplified by long-range PCR. Sequencing libraries were prepared using ONT Ligation Sequencing Kit. Each library was loaded onto a flow cell for sequencing on ONT GridION Mk1 running MinKNOW control software. FASTQ files were aligned to hg38 using minimap2. Variants were called using Clair3 and phased using WhatsHap. Integrative Genomics Viewer (IGV) was used for visualization of the phased variants. Results We successfully phased all the multiple DSG2 variants found in the 15 proband. A typical result of amplicon-based LRS was shown in Figure B. It was IGV screen shot of reads at DSG2 containing c.874C&amp;gt;T (p.R292C) and c.1481A&amp;gt;C (p.D494A). The reads colored in red belonged to one haplotype, while the ones in blue belonged to the other. Each of the two variants was on different color reads, indicating they were compound heterozygous variants. Using LRS, we confirmed all the 15 probands had compound heterozygous variants in DSG2. Overall, the 62 probands (40.5%) with DSG2 variants were recessive variant carriers (Figure A). Conclusions Japanese ARVC was mainly caused by autosomal recessive variants in DSG2. Clarifying the zygosity of causative variants is crucial for the diagnosis in recessive diseases including Japanese ARVC. Amplicon-based LRS was helpful for phasing the multiple DSG2 variants directly without genetic testing of the parents.Figure AFigure B

AAV-based TCAP delivery rescues mitochondria dislocation in limb-girdle muscular dystrophy R7.

Limb-girdle muscular dystrophy R7 is a rare genetic disease caused by homozygous or compound heterozygous variants in the titin-cap (TCAP) gene that results in the absence of the protein telethonin. The primary pathological features of limb-girdle muscular dystrophy R7 are fiber size variation, nuclear centralization, and abnormal mitochondrial distribution. The mechanisms underlying this disease are unclear, and there is currently no specific treatment for limb-girdle muscular dystrophy R7. This study established a Tcap-deficient mouse model to explore the disease mechanism of mitochondria dislocation and potential therapeutic strategies. We use methods such as proteomics, immunofluorescence, histopathological staining, and western blotting to explore the mechanism of mitochondrial dislocation. Moreover, in the quest for a prospective therapeutic intervention for this disorder, the adeno-associated virus serotype 2/9 was employed to deliver the Tcap gene into the muscles of these mice, facilitating preclinical experimentation. After 2 months and 7 months, the muscular phenotype was evaluated and selected mice were humanely euthanized for subsequent molecular and histological analysis. The phenotype of Tcap-/- mice mimicked that observed in individuals diagnosed with limb-girdle muscular dystrophy R7. This study elucidated the mechanism of mitochondrial dislocation in limb-girdle muscular dystrophy R7. Through our in vitro experiments, we discovered that telethonin aids in preserving the integrity of desmin by preventing truncation at the N-terminus. Additionally, telethonin combined with desmin and colocalized at the Z-disc. Research has shown that the Tcap gene plays a crucial role in controlling the desmin cytoskeleton organization. The absence of telethonin leads to a collapsed desmin cytoskeleton. This causes disorganization of the mitochondrial network, leading to mitochondrial dysfunction. In addition, the study investigated the efficacy of adeno-associated virus (AAV)-mediated Tcap replacement in Tcap-/- mice. By intramuscular delivery of AAV, we observed dramatic improvements in muscle phenotype, muscle pathology, CK levels, muscle magnetic resonance imaging, mitochondrial network organization, and mitochondrial function. The results of this study demonstrated that telethonin deficiency led to desmin cytoskeleton collapse that caused mitochondrial dislocation. AAV-mediated replacement therapy could be a promising safe and efficient treatment option for limb-girdle muscular dystrophy R7. The study highlights the potential of AAV-mediated replacement therapy for specific types of limb-girdle muscular dystrophy.

Association of LONP1 gene with epilepsy and the sub-regional effect

The LONP1 gene encodes Lon protease, which is responsible for degrading damaged or misfolded proteins and binding mitochondrial DNA. Previously, LONP1 variants have been identified in patients with cerebral, ocular, dental, auricular, and skeletal anomalies (CODAS syndrome) and mitochondrial diseases. Seizures were occasionally observed. However, the association between LONP1 and epilepsy remains elusive. In this study, we performed trio-based whole-exome sequencing in a cohort of 450 patients with unexplained epilepsy and identified four pairs of compound heterozygous LONP1 variants in four unrelated cases. All patients exhibited good responses to anti-seizure medications and demonstrated no developmental delay or intellectual disabilities. The variant allele frequencies observed in this study were absent or low in the general population and were significantly lower than those of benign variants. At least one variant in each biallelic pair affected hydrogen bonding and/or altered protein stability. The CODAS syndrome-associated variants were concentrated in the AAA+ module, especially the α domain. Four of the five mitochondrial disease-associated variants were located in the AAA + domain and the NTD5H and NTD3H subdomains. In contrast, each of the biallelic variants from the patients with pure epilepsy had one variant located in the linker domain, and the other variant located in the mitochondrial targeting sequence or P domain. This study suggested that LONP1 gene is potentially a novel candidate gene for pure epilepsy. The phenotypic variation is associated with the sub-regional effects of variants.

Are rare heterozygous SYNJ1 variants associated with Parkinson’s disease?

Previous studies have established that rare biallelic SYNJ1 mutations cause autosomal recessive parkinsonism and Parkinson’s disease (PD). We analyzed 8165 PD cases, 818 early-onset-PD (EOPD, < 50 years) and 70,363 controls. Burden meta-analysis revealed an association between rare nonsynonymous variants and variants with high Combined Annotation-Dependent Depletion score (> 20) in the Sac1 SYNJ1 domain and PD (Pfdr = 0.040). A meta-analysis of EOPD patients demonstrated an association between all rare heterozygous SYNJ1 variants and PD (Pfdr = 0.029).

Biallelic germline DDX41 variants in a patient with bone dysplasia, ichthyosis, and dysmorphic features.

DDX41 (DEAD‑box helicase 41) is a member of the largest family of RNA helicases. The DEAD-box RNA helicases share a highly conserved core structure and regulate all aspects of RNA metabolism. The functional role of DDX41 in innate immunity is also highly conserved. DDX41 acts as a sensor of viral DNA and activates the STING-TBK1-IRF3-type I IFN signaling pathway. Germline heterozygous variants in DDX41 have been reported in familial myelodysplasia syndrome (MDS)/acute myeloid leukemia (AML) patients; most patients also acquired a somatic variant in the second DDX41 allele. Here, we report a patient who inherited compound heterozygous DDX41 variants and presented with bone dysplasia, ichthyosis, and dysmorphic features. Functional analyses of the patient-derived dermal fibroblasts revealed a reduced abundance of DDX41 and abrogated activation of the IFN genes through the STING-type I interferon pathway. Genome-wide transcriptome analyses in the patient's fibroblasts revealed significant gene dysregulation and changes in the RNA splicing events. The patient's fibroblasts also displayed upregulation of periostin mRNA expression. Using an RNA binding protein assay, we identified DDX41 as a novel regulator of periostin expression. Our results suggest that functional impairment of DDX41, along with dysregulated periostin expression, likely contributes to this patient's multisystem disorder.

BCL11A intellectual developmental disorder: defining the clinical spectrum and genotype-phenotype correlations.

An increasing number of individuals with intellectual developmental disorder (IDD) and heterozygous variants in BCL11A are identified, yet our knowledge of manifestations and mutational spectrum is lacking. To address this, we performed detailed analysis of 42 individuals with BCL11A-related IDD (BCL11A-IDD, a.k.a. Dias-Logan syndrome) ascertained through an international collaborative network, and reviewed 35 additional previously reported patients. Analysis of 77 affected individuals identified 60 unique disease-causing variants (30 frameshift, 7 missense, 6 splice-site, 17 stop-gain) and 8 unique BCL11A microdeletions. We define the most prevalent features of BCL11A-IDD: IDD, postnatal-onset microcephaly, hypotonia, behavioral abnormalities, autism spectrum disorder, and persistence of fetal hemoglobin (HbF), and identify autonomic dysregulation as new feature. BCL11A-IDD is distinguished from 2p16 microdeletion syndrome, which has a higher incidence of congenital anomalies. Our results underscore BCL11A as an important transcription factor in human hindbrain development, identifying a previously underrecognized phenotype of a small brainstem with a reduced pons/medulla ratio. Genotype-phenotype correlation revealed an isoform-dependent trend in severity of truncating variants: those affecting all isoforms are associated with higher frequency of hypotonia, and those affecting the long (BCL11A-L) and extra-long (-XL) isoforms, sparing the short (-S), are associated with higher frequency of postnatal microcephaly. With the largest international cohort to date, this study highlights persistence of fetal hemoglobin as a consistent biomarker and hindbrain abnormalities as a common feature. It contributes significantly to our understanding of BCL11A-IDD through an extensive unbiased multi-center assessment, providing valuable insights for diagnosis, management and counselling, and into BCL11A's role in brain development.

CSF d18:1 sphingolipid species in Parkinson disease and dementia with Lewy bodies with and without GBA1 variants

Variants in GBA1 result in dysregulated sphingolipids. We investigated five CSF d18:1 sphingolipid species in a longitudinal multicenter cohort comprising people with Parkinson’s Disease and Dementia with Lewy bodies with and without GBA1 variants and healthy controls. We found no increase of sphingolipid species in heterozygous GBA1 variant participants and no effect on development of cognitive impairment. Thus, CSF d18:1 sphingolipids are not suitable as state markers in Parkinson’s Disease.

A Leaky Deep Intronic Splice Variant in CLRN1 Is Associated with Non-Syndromic Retinitis Pigmentosa

Background: Inherited retinal diseases (IRDs) are clinically complex and genetically heterogeneous visual impairment disorders with varying penetrance and severity. Disease-causing variants in at least 289 nuclear and mitochondrial genes have been implicated in their pathogenesis. Methods: Whole exome sequencing results were analyzed using established pipelines and the results were further confirmed by Sanger sequencing and minigene splicing assay. Results: Exome sequencing in a 51-year-old Ashkenazi Jewish patient with non-syndromic retinitis pigmentosa (RP) identified compound heterozygous variants in the CLRN1 gene: a known pathogenic missense [p.(N48K)] and a novel deep intronic variant c.254-643G&gt;T. A minigene splicing assay that was performed aiming to study the effect of the c.254-643G&gt;T variant on CLRN1 pre-mRNA splicing revealed the inclusion of a pseudo-exon that was also reported to be included in the transcript due to an adjacent variant, c.254-649T&gt;G. However, unlike the reported c.254-649T&gt;G variant, c.254-643G&gt;T showed aberrant splicing in a leaky manner, implying that the identified variant is not totally penetrant. Conclusion: We report on a novel deep intronic variant in CLRN1 causing non-syndromic RP. The non-syndromic phenotype observed in this index case may be attributed to the leaky nature of this variant, which is causing some normal transcripts to be produced.

Epidermolytic Hyperkeratosis Type 1 with a New Heterozygous Mutation in KRT1 Gene: A Case Report

Background: Epidermolytic hyperkeratosis (EHK) formerly known as bullous ichthyosiform erythroderma, is a rare autosomal dominant inheritance condition with a prevalence ranging from 1:200,000 to 1:300,000. The underlying etiology of which is a mutation in the genes responsible for keratin proteins synthesis, primarily in KRT1 and KRT10 genes, cataloged under OMIM number 113800. Clinicopathological presentations include blistering in the neonatal period followed by ichthyotic hyperkeratosis in childhood and adolescence, characterized by the hallmark features of generalized dry skin, scaling, hyperkeratosis, and frequently associated with erythroderma. EHK may present with or without palmoplantar keratoderma involvement, depending on the keratin gene variant. Case report: A 24-year-old male of Arab descent was born with diffuse skin hyperkeratotic plates featuring erythematous fissures, covering his entire body, resembling a collodion baby. His birth was full-term via cesarean section without complications, although he later developed developmental dysplasia of the hip. By the time he started primary school, he began experiencing severe thickening of the skin around his joints, reducing flexibility and leading to contractures and significant disfigurement. He is undergoing treatment with acitretin. Genetic testing using Next-Generation Sequencing (NGS) was performed to identify the responsible gene, revealing a novel heterozygous variant in the KRT1 gene (OMIM 139350), while no variant was detected in the KRT10 gene. Conclusion: EHK type 1 manifests with a new heterozygous variant in the KRT1 gene. This rare disorder, associated with variant in genes related to keratin production such as KRT1 and KRT10, results in distinctive skin features present from birth, as well as joint problems and fungal foot infections. Genetic testing has confirmed the presence of a variant in the KRT1 gene.

A Compound Heterozygous Pathogenic Variant in ZP2 Gene Causes Female Infertility.

The oocyte maturation defect 6 is an autosomal recessive hereditary disease caused by a homozygous variant in ZP2 gene. It is characterized by female primary infertility due to an abnormally thin zona pellucida (ZP) and defective sperm binding. Here we identified a compound heterozygous variant (c.1924C > T and c.1695-2A > G) in ZP2 gene in a Chinese Han family. Quantitative real-time PCR showed that the variant c.1924C > T significantly decreased the expression of truncated ZP2message RNA by the nonsense-mediated decay pathway. Minigene assays showed the c.1695-2A > G variant led to an extra-61-nt preservation of intron 15 at the junction between exons 15 and 16 during transcription. Both variants (c.1924C > T and c.1695-2A > G) resulted in truncated ZP2 proteins (p.R642X and p.C566Hfs*2) that lost the transmembrane domain, which prevented the secretion of the mutant ZP2 proteins and produced a structurally abnormal ZP, thus resulting in female infertility. This study further elucidated the pathogenic mechanism of these two variants and provided new support for the genetic diagnosis of female infertility.

CLCN2-related leukoencephalopathy with novel compound heterozygous variants followed with magnetic resonance imaging over 17 years: a case report

BackgroundCLCN2-related leukoencephalopathy (CC2L) is a rare autosomal recessive disorder caused by biallelic variants of CLCN2, which encodes chloride channel 2. Although CC2L is associated with distinct radiological features, it presents with a wide range of clinical features.Case presentationA 34-year-old woman presented to our hospital with a sudden onset of vertigo with headache. The patient reported intermittent headaches and tingling in both arms since the age of 31 years. On the first visit, the patient was alert and neurologically intact, except for slight hyperreflexia of the limbs without laterality. Head magnetic resonance imaging (MRI) showed high-intensity signals on axial T2-weighted fluid-attenuated inversion recovery and diffusion-weighted images bilaterally in the posterior limbs of the internal capsules, cerebral peduncles, superior and middle cerebellar peduncles, decussation of superior cerebellar peduncles, and central tegmental tract. All the patient’s symptoms were resolved or eased following supportive care. The patient stopped attending our hospital at the age of 46 years. At 51 years of age, the patient revisited our hospital because of the recurrence of vertigo, headache, and nausea. She did not present with any abnormalities by neurological examination. Head MRI showed widespread high-intensity signals similar to those 17 years ago. Genetic testing revealed compound heterozygous variants in CLCN2 (NM_004366.6): a novel variant c.1828 C > T, p.(Arg 610*) from her father and c.61dup, p.(Leu21Profs*27) from her mother. The patient was finally diagnosed with CC2L. She received supportive treatment, which made her symptoms manageable.ConclusionsThis is a detailed report of a patient with adult-onset CC2L who was successfully diagnosed and followed up with head MRI. This report provides new insights into CC2L and highlights its persistent, distinct, and stable characteristics observed in head MRI over one decade and the difficulty in forming a diagnosis without MRI when patients have minimal and common symptoms, such as in the present case.

Biallelic pathogenic variants in the LSS gene cause congenital alopecia-cataract syndrome.

Biallelic variants in the LSS gene have been reported in individuals affected by alopecia-intellectual disability syndrome 4, cataract 44, hypotrichosis 14, and palmoplantar keratoderma-congenital alopecia syndrome type 2. The present report described a Chinese girl with congenital alopecia universalis, cataract, esotropia, and nystagmus caused by compound heterozygous variants of c.1025T>G (p.Ile342Ser) and previously unreported c.1011G>A (p.Pro337=) in the LSS gene. Minigene assay confirmed the synonymous variant Pro337= at the edge of exon 9 could produce a novel splice site, leading to a 46-bp insertion of the 5' sequence of the intron 9, likely resulting in a frameshift effect. We consider that the clinical manifestations of this case represent a new type of LSS-related disease, namely congenital alopecia-cataract syndrome (CACS). Our data expand the phenotypic and genetic spectrum of LSS-related diseases.