Rare Manifestation Research Articles

ERN ReCONNET-SLICC-SLEuro expert consensus on the therapeutic management of rare systemic lupus erythematosus manifestations.

ERN ReCONNET-SLICC-SLEuro expert consensus on the therapeutic management of rare systemic lupus erythematosus manifestations.

Metastatic basal cell carcinoma: Case series and literature review.

Metastatic basal cell carcinoma: Case series and literature review.

Epilepsy as the Main Clinical Manifestation of Congenital Hypothyroidism: A Rare Case Report

Background: Congenital hypothyroidism (CH) is defined as a deficiency of thyroid hormones present at birth and is one of the most common causes of intellectual disability. CH shows several manifestations, but it is rarely reported that CH manifests as epilepsy. To our knowledge, this rare manifestation of congenital hypothyroidism has only been reported four times previously. The potential association between CH and epilepsy remains unclear. Case: We reported a rare case of a 1-year-old child who presented to the emergency department with complaints of recurrent seizures. Laboratory results showed increased TSH levels and decreased FT4 levels. Electroencephalography (EEG) results were expected. The patient was diagnosed with epilepsy and congenital hypothyroidism. The patient received stabilization therapy in the ER and was admitted to the PICU for 7 days. During hospitalization and a seven-day evaluation at home, the patient did not experience any further seizures. Discussion: Epilepsy and congenital hypothyroidism can affect each other through three known pathogeneses: mitochondrial dysfunction, oxidative stress, and failure of amino acid regulation in the brain. Long-term use of some anti-epileptic drugs is known to reduce thyroid hormone levels. Conclusion: Thyroid hormones play an essential role in various aspects of epilepsy. Thyroid function screening in patients with epilepsy may be advisable, especially in patients with developmental disorders and relevant symptoms.

Myxedema madness: exploring a reversible psychosis with case review and discussion

Myxedema madness is a rare but severe neuropsychiatric manifestation of profound hypothyroidism, frequently mistaken for primary psychiatric illness due to its striking psychotic symptoms. We present the case of a 52-year-old woman with no prior psychiatric history who developed progressive persecutory delusions, auditory hallucinations, cognitive impairment, and psychomotor slowing over three months. Despite initial treatment with antipsychotics, her symptoms persisted. A broader clinical assessment, prompted by systemic features including weight gain, cold intolerance, constipation, menorrhagia, and generalized swelling, led to the diagnosis of severe hypothyroidism (TSH >100 mIU/L, free T4 <0.3 ng/dL) due to Hashimoto’s thyroiditis. Levothyroxine replacement therapy resulted in the complete resolution of both psychiatric and systemic symptoms within six weeks. This case emphasizes the necessity of thyroid function screening in atypical psychosis, underscoring how early recognition can prevent misdiagnosis and unnecessary psychiatric treatment. A comprehensive discussion contextualizes this case within the existing literature, reinforcing its clinical significance.

Therapeutic effect of adalimumab in the treatment of intestinal Behçet's disease in children

ObjectiveIntestinal Behçet's disease is a rare but severe manifestation of Behçet's disease, particularly in pediatric populations. Currently, there is no cure for intestinal Behçet's disease, and the goal of treatment is to control acute episodes and reduce inflammation. Adalimumab, a tumor necrosis factor-alpha (TNF-α) inhibitor, has shown promise in adult patients, but data on its efficacy and safety in children are limited. The aim of this study was to evaluate the efficacy and safety of adalimumab in the treatment of intestinal Behçet's disease in children.MethodsA retrospective analysis was conducted on 8 children with intestinal Behçet's disease treated with adalimumab at Xi'an Children's Hospital from January 2021 to December 2024. Clinical symptoms, endoscopic findings, and inflammatory markers were assessed before and after treatment. Efficacy was evaluated on the basis of symptom resolution, ulcer healing, and changes in inflammatory markers.ResultsThe cohort included 4 males and 4 females, with an average age of 11.9 ± 1.4 years and a disease course of 10.5 (6.75, 22.5) months. All patients presented with gastrointestinal symptoms, including abdominal pain (n = 7), vomiting (n = 1), and complications such as intestinal obstruction (n = 3) and perforation (n = 1). Colonoscopy revealed ileocecal ulcers in 7 patients and only terminal ileal ulcers in 1 patient. After treatment with adalimumab, complete resolution of clinical symptoms was observed in all patients. Gastrointestinal endoscopy revealed that 6 patients had completely healed ulcers, while the remaining 2 patients had ulcers that were reduced to 50% of their original size. The levels of inflammatory markers significantly decreased, with the erythrocyte sedimentation rate (ESR) decreasing from 44.63 ± 43.48 mm/h to 10.50 ± 7.65 mm/h (p = 0.046) and the high sensitivity C-reactive protein (hs-CRP) level decreasing from 43.87 ± 39.10 mg/L to 0.96 ± 0.67 mg/L (p = 0.017). On the basis of clinical symptoms and endoscopic findings, 6 patients (75%) achieved complete remission, and 2 patients (25%) showed improvement. Adalimumab was well tolerated, with only one case of mild eczema reported.ConclusionAdalimumab is safe and effective in the treatment of intestinal Behçet's disease in children.

Wernicke encephalopathy presenting with rare clinical findings: bilateral VI cranial nerve palsy and pontine lesion

Wernicke encephalopathy (WE) is a serious acute neurological condition that is commonly associated with vitamin B1 (thiamine) deficiency due to alcohol abuse, albeit it can also occur in non-alcoholic settings. In cases of thiamine deficiency, a clinical diagnosis of WE is considered when two or more of the classic features—such as ophthalmoplegia, gait ataxia, and confusion—are present. A rare clinical manifestation of WE, including bilateral sixth cranial nerve palsy, ataxia, and pontine involvement on MRI, is described in this report. A 36-year-old male was admitted with complaints of diplopia for five days, along with a one-month history of hallucinations and insomnia. His medical history revealed chronic alcohol dependence, including recent consumption of homemade alcohol shortly before his complaints began. On neurological examination, bilateral restricted lateral gaze was observed. Axial T2-weighted MRI images of the brain showed a hyperintense lesion at the pontine midline. The patient was admitted with a preliminary diagnosis of WE and started on thiamine therapy at 500 mg/day for five days, followed by 200 mg/day and then 100 mg/day, each administered for an additional five days. During the early stages of WE, patients typically exhibit characteristic symptoms such as alterations in mental status, ophthalmoplegia, and ataxia. On T2-weighted MRI, Wernicke encephalopathy is indicated by hyperintense lesions in brain regions with high carbohydrate metabolism, particularly involving the ventral thalamus, hypothalamus, mammillary bodies, periaqueductal gray matter, and the floor of the fourth ventricle. This case has been presented to highlight a rare clinical presentation of Wernicke encephalopathy.

Myxedema psychosis, a rare complication of untreated hypothyroidism

Myxedema psychosis, also known as myxedema madness, is a rare neuropsychiatric manifestation of untreated or inadequately treated hypothyroidism. We report the case of a 46-year-old woman presenting to the emergency department with acute psychiatric symptoms, including confusion, hallucinations, and delusions. Physical examination revealed classic signs of hypothyroidism, such as periorbital edema, dry skin, and diffuse hair loss. Laboratory results showed a markedly elevated thyroid-stimulating hormone (TSH) level of 45.76 mU/L and a severely reduced free thyroxine (T4) level (< 1.0 pmol/L), confirming the diagnosis of myxedema psychosis. Intravenous administration of levothyroxine and liothyronine (T3) led to rapid resolution of psychotic symptoms. This case report underscores the critical need to evaluate somatic causes, including hypothyroidism in patients presenting with acute psychiatric symptoms. Timely diagnosis and appropriate thyroid hormone replacement therapy can result in full recovery.

Surgical intervention for peripheral plexiform schwannoma of the sciatic nerve: a pediatric case study

Plexiform Schwannoma, or neurilemmomas, is a rare and benign manifestation of peripheral nerve sheath tumors. The tumor mostly arises from the gradual growth of Schwann cells. These nerve tumors occur in several sites, with the most prevalent being the head, or neck, or even upper extremities. This tumor predominantly manifests in individuals aged 30 to 40 years and is seen equally in both sexes, with these tumors generally measuring less than 2 cm in size. A 14-year-old boy was referred to Oriana Specialty Hospital, Sharjah, UAE, with a one-year history of vague pain in the middle third posterior aspect of the right thigh accompanied by mild tenderness but no peripheral neurological deficit. Magnetic resonance imaging (MRI) of the right thigh revealed a lesion, and a true-cut biopsy confirmed the diagnosis of a peripheral plexiform Schwannoma arising from the sciatic nerve. On 29 December 2024, a surgical excision of the right thigh sciatic nerve Schwannoma was carried out. A posterior midline thigh incision was made, and the procedure was done with advanced techniques, including the use of a microscope and intraoperative nerve stimulator, to ensure precise tumor dissection from the sciatic nerve. The entire Schwannoma, measuring 24×5.5 cm, was successfully excised. There were excellent recoveries post operatively with no neurological deficits or complications of surgery. He was mobilized with full weight-bearing three hours after the surgery and discharged the next day on oral medications. This particular case testifies to the complete excision of a tumor through proper surgery techniques, preserving the neurological function, with promising outcomes for similar cases.

An ST elevation myocardial infarction with multisystemic embolization: a shocking and striking first presentation of antiphospholipid syndrome: a case report

Abstract Introduction Anti-phospholipid syndrome is characterized by venous and/or arterial thrombosis in the presence of anti-phospholipid antibodies. We report a rare and dramatic manifestation of the syndrome: thrombotic coronary occlusion leading to myocardial infarction, resulting in multiple intra-LV thrombi responsible for multisystemic embolization Case presentation We report the case of a 38-year-old Caucasian woman, who presented to the emergency department with acute chest pain. On initial clinical examination, the patient was tachycardic at 123 bpm with a correct blood pressure of 127/69 mmHg. The ECG showed sinus tachycardia at 125 bpm with QS waves in the anteroseptal with persistent ST-segment elevation in the same territory. Transthoracic echocardiography revealed LVEF of 35% with several intra-LV thrombi. Troponin Ic was elevated at 5668 ng/L. The diagnosis of myocardial infarction was suspected and the patient was treated as such. 8 hours after admission, the patient presented with an embolization to both common femoral arteries which was treated by Fogarty embolectomy. The patient underwent coronary angiography, which revealed thrombotic occlusion of the proximal left anterior descending artery. A Cerebro-thoraco-abdomino-pelvic CT scan found a right renal infarct and a splenic infarct. Lab tests revealed positive anti-cardiolipin antibodies. Anti-phospholipid syndrome was confirmed and the patient was treated using aspirin and vitamin K antagonists. The evolution was marked by complete resolution of LV thrombi and the patient is actually asymptomatic apart from a slight exertional dyspnea. Conclusion Anti-Phospholipid Syndrome is an autoimmune disorder whose complications can be life-threatening and/or functionally disabling. Arterial thrombosis can cause dramatic complications.

Perisplenic mass as initial diagnosis of malignant peritoneal mesothelioma.

Perisplenic masses or collections are rare findings on imaging examinations. The differential diagnostic spectrum is broad. We report the case of an 84-year-old man who presented to our emergency department with fatigue, unwanted weight loss, loss of appetite and abdominal pain. In B-mode ultrasound a very hypoechoic collection circularly located around the spleen was seen. A splenic hematoma or an abscess were primarily suspected. Performing contrast-enhanced ultrasound examination the perisplenic collection was surprisingly strongly contrasted in the arterial phase. An additional abdominal CT confirmed the mass in the left upper abdomen circularly around the spleen, compressing the left colic flexure and beginning to infiltrate the gastric fundus. An ultrasound-guided tissue biopsy was taken via a percutaneous intercostal approach, which resulted in the diagnosis of a low-grade epithelioid malignant peritoneal mesothelioma (MPM). MPM often presents with diffuse multifocal involvement of the peritoneal lining, however a unifocal manifestation of MPM is uncommon in general. A perisplenic mass manifestation of malignant peritoneal mesothelioma is an extremely rare occurrence. This case highlights the diagnostic challenges posed by the rare perisplenic manifestation of MPM.

Acute Rhabdomyolysis as a Rare Manifestation of Hypothyroidism: A Case Report and Literature Review

Acute Rhabdomyolysis as a Rare Manifestation of Hypothyroidism: A Case Report and Literature Review

Wilms Tumor and Paraneoplastic Syndromes: Unusual Presentation With Acquired von Willebrand Disease, Polycythemia and Hyperviscosity-A Comprehensive Case Report and Literature Reviews.

A 10-month-old child presenting with renal tumor with polycythemia, acquired von Willebrand disease, and elevated serum hyaluronic acid, leading to a diagnosis of Wilms tumor. Laboratory profile showed elevated levels of hemoglobin and hematocrit, prolonged aPTT, and high levels of hyaluronic acid and erythropoietin, which normalized after chemotherapy and tumor resection. She had a complete response and has remained in remission. Paraneoplastic syndromes are rare manifestations of Wilms tumor (WT). The simultaneous occurrence of distinct types, as demonstrated in this report (polycythemia, hyperviscosity, and coagulopathy), has not been previously reported. This unique presentation poses a challenge for both diagnostic and clinical management.

Childhood Lupus-Associated Protein-Losing Enteropathy (LUPLE): A Case Report and Review of the Literature.

Protein-losing enteropathy (PLE) is a rare condition characterized by clinical findings such as edema, ascites, pleural effusion, and diarrhea due to excessive protein loss from the gastrointestinal system. Although systemic lupus erythematosus (SLE) is rare in childhood, PLE can be the first presenting feature; this condition is referred to as lupus-associated protein-losing enteropathy (LUPLE). Protein-losing enteropathy (PLE) is an uncommon condition resulting from excessive protein loss in the gastrointestinal system. Our case shows that PLE can be the initial presentation of SLE, which is a rare manifestation in childhood. PLE, a rare complication of lupus, tends to be more severe in children, and the diagnostic process can be challenging. This case report presents a 7-year-old girl who presented with abdominal distension, generalized edema, chronic diarrhea, and weakness. Despite treatment, the recurrence of symptoms and the addition of new joint findings led to further investigations, which revealed positive anti-dsDNA and low complement levels, resulting in a diagnosis of systemic lupus erythematosus. The patient's clinical condition improved with steroid, azathioprine, and hydroxychloroquine treatments. This case highlights the importance of considering SLE in the differential diagnosis of PLE and underscores the significance of recognizing the rare presentations of childhood lupus.

Clinicopathological features of feline emphysematous cholecystitis: five cases (2017-2022).

Emphysematous cholecystitis is a rare manifestation commonly associated with acute cholecystitis complicated by gas-producing organisms. The study aimed to describe the clinical and pathological features of emphysematous cholecystitis in cats. The databases of 32 Diplomate-led Small Animal Internal Medicine referral centres located in the United Kingdom and Ireland were searched. Five cases with confirmed feline emphysematous cholecystitis were identified and retrospectively reviewed. The main clinical signs included inappetence (100%), vomiting (80%) and lethargy (60%). The main abnormalities on physical examination were jaundice (60%), abdominal discomfort (40%) and organomegaly (40%). The most common laboratory abnormalities were leucocytosis (range 1.12- to 2.3-fold increase), lymphopenia (range 0.4- to 0.93-fold decrease), increased serum alanine transaminase activity (range 2.02- to 11.72-fold increase) and hyperbilirubinemia (range 4.8- to 18.58-fold increase). Abdominal imaging including ultrasound or computed tomography showed dilated intra- and extra-hepatic bile ducts and luminal and/or intra-luminal gas foci in all cases. Bacterial culture identified a moderate growth of Corynebacterium spp. in one case and Enterococcus spp. in another case. Three cats survived to discharge following cholecystectomy; two of which had medical stabilisation prior to surgery. Two cats died; one was treated medically and the other treated surgically without prior medical stabilisation. This is the first time that emphysematous cholecystitis has been described in a cohort of cats. It warrants consideration as a rare differential diagnosis in cats presenting with increased serum alanine transaminase activity and bilirubin. Medical stabilisation with antibiotic therapy followed by cholecystectomy may offer a favourable outcome.

Uveal Melanoma and the Lynch Syndrome Tumor Spectrum

To date, no environmental factors and few therapeutic options are known for uveal melanoma (UM), the most common malignant intraocular primary tumor in adults. Identification of new predisposition factors could lead to better monitoring and possibly improved treatments of patients with UM. To identify new genetic alterations predisposing for UM. This was a prospective cohort study conducted at Institut Curie in Paris, France, among 381 consecutive patients diagnosed with UM between July 2021 and February 2023. UM was diagnosed clinically by ophthalmologists, and a senior pathologist confirmed the diagnosis when tumor or biopsy was available. All participants received genetic counseling and consented to extended genetic testing. A panel of 122 genes predisposing to cancer were analyzed by targeted sequencing on germline DNA from these patients. Frequency of pathogenic variants (PVs) in genes from a targeted panel, with classification of germline PVs done according to the American College of Medical Genetics and Genomics guidelines and the French Unicancer Genetics Group. A total of 79 PVs were identified in 70 participants (41 female and 29 male; mean [SD] age, 60.6 [15.3] years). Among them, 21 were found in clinically relevant genes, with an enrichment in the mismatch repair (MMR) genes, involved in Lynch syndrome, a frequent predisposition to colon and endometrial cancers. This finding suggested MMR germline PVs could also predispose to UM. One tumor was available from a participant carrying a MLH1 germline PV. The tumor exhibited a monosomy 3 with loss of the wild-type allele of MLH1, located on chromosome 3. Loss of expression of MLH1 was observed by immunohistochemistry, and MMR variant signatures SBS6, ID1, and ID2 were identified from the whole-genome sequencing of this tumor, supporting the possibility that MLH1 contributes to the oncogenesis of this UM. This prospective germline study on patients with UM provided evidence supporting the notion that MMR germline alterations are enriched among patients with UM and may contribute to oncogenesis of UM, and that UM may therefore be a rare tumor manifestation of Lynch syndrome.

Inverse Gottron’s sign in Anti TIF1 gamma positive juvenile dermatomyositis

Dermatomyositis is a rare idiopathic inflammatory myopathy characterized by distinctive cutaneous findings and proximal muscle weakness. We describe a 15-year-old girl who presented with a six-month history of heliotrope rash and V-sign erythema, accompanied by symmetrical proximal muscle weakness. Further examination revealed Gottron’s papules and the rare manifestation of inverse Gottron’s papules. Laboratory evaluation revealed elevated muscle enzymes. An extended myositis antibody panel demonstrated strong anti-TIF1γ positivity, while anti-MDA5, Mi-2, Jo-1, and other myositis-specific antibodies were negative, confirming a diagnosis of dermatomyositis. Screening excluded interstitial lung disease and underlying malignancy. Inverse Gottron’s papules are usually associated with anti-MDA5 dermatomyositis and rapidly progressive interstitial lung disease; their occurrence in anti-TIF1γ–positive juvenile cases is scarcely documented. Treatment with oral prednisolone and methotrexate led to gradual resolution of cutaneous lesions and muscular symptoms. This case documents the rare coexistence of inverse Gottron’s papules and anti-TIF1γ seropositivity in juvenile dermatomyositis, underscores the diagnostic utility of this atypical palmar cutaneous sign, highlights the clinical phenotype associated with anti-TIF1γ positivity, and emphasizes the importance of continued malignancy surveillance despite the lower cancer risk in pediatric cohorts.

A global perspective on the spatial representation of climate extremes from km-scale models

Abstract Weather and climate extremes are rare manifestations of climate variability that can severely impact society and the environment. To investigate their properties and changes on a global scale, observational records are often complemented by climate models such as those from the latest Coupled Model Intercomparison Project (CMIP6). However, typical CMIP6 models have a grid spacing of about 100 km and, therefore, do not allow the representation of extremes at local scales important for impacts. Here, we provide a global view on the information lost at such resolutions, focusing on temperature and precipitation extremes. We draw on two next-generation, km-scale global climate models, run with a grid spacing of about 10 km, and regrid them to a range of coarser resolutions. From the regridded data, we then investigate the spatial sub-grid variability hidden at the CMIP6-like 100 km grid spacing to quantify the effect resolution has on the representation of extremes globally. We find clear patterns of such a resolution effect on a diverse set of temperature extremes, particularly in mountainous areas, at coastlines, and along large rivers. For the example of annual maximum temperature, the difference between the 10 km and 100 km grid spacings can exceed 10 ∘C. For precipitation, globally aggregated low and high extremes are shown to be underestimated at coarse resolution, with the strongest spatial signals emerging in regions with complex topography and in the tropics. Our results quantify existing knowledge and demonstrate the importance of spatial resolution for the representation of climate extremes, in particular for hotspot regions such as coastlines, which often coincide with densely populated areas. The advent of ever higher resolved global models, hence, allows improved estimates of local climate impacts and related risk assessments with global coverage.

A Case of Primary Cutaneous Cryptococcosis in the Setting of Tofacitinib Therapy for Rheumatoid Arthritis

Primary cutaneous cryptococcosis is a rare manifestation of Cryptococcus infection, which can present with diverse clinical manifestations, ranging from solitary nodules or papules to ulcerative lesions or cellulitis-like erythema. A 49-year-old female, a known case of rheumatoid arthritis who was on daily 4 mg of methyl prednisolone and 10 mg of tofacitinib, presented with painful, rapidly progressing ulcers over the right flank for 15 days. A differential diagnosis of pyoderma gangrenosum was considered since patient had rheumatoid arthritis. Histopathological examination of the skin biopsy from the edge of the ulcer showed granulomatous infiltrate with budding yeast forms surrounded by a thick capsule, suggestive of Cryptococcus neoformans . Fungal culture showed milky and creamy colonies on Sabouraud dextrose agar. Patient was initiated on oral Fluconazole 200 mg daily for three months. The ulcers healed completely after three months of treatment. To conclude, in patients with rapidly progressing ulcers, a differential diagnosis of cutaneous cryptococcosis must also be considered.

Clinical Features in VEXAS syndrome: a systematic review.

To systematically characterise the complete phenotypic spectrum of VEXAS (vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic) syndrome through comprehensive analysis of all published cases since its discovery in 2020. We conducted a systematic review following PRISMA guidelines across five databases. Studies reporting genetically confirmed VEXAS cases were included. To minimise duplicate counting while maximising data utility, we applied stringent inclusion criteria. Prevalence estimates were calculated using Wilson score intervals. Results were discussed, with secondary analysis focusing on rare manifestations of the disease, and clinical recommendations as appropriate. Analysis of 720 patients from 33 case reports and 21 case series across 32 countries revealed cutaneous involvement as the predominant manifestation (81.8%, 95% CI: 78.8-84.5%), followed by constitutional symptoms (69.4%, 95% CI: 66.0-72.7%) and respiratory disease (61.3%, 95% CI: 57.6-64.7%). Joint involvement (47.3%, 95% CI: 43.5-51.2%), ocular disease (44.3%, 95% CI: 40.5-48.2%), and venous thromboembolism (41.8%, 95% CI: 38.3-45.4%) were also common. Myelodysplastic syndrome occurred in 35.8% (95% CI: 32.3-39.4%) of patients. Previously under-recognised manifestations included significant respiratory involvement and a broad spectrum of vascular complications. Rare but clinically significant features included cardiac involvement (7.6%), renal disease (7.0%), and central nervous system manifestations (7.8%). This systematic review provides the most comprehensive characterisation of VEXAS syndrome to date, establishing robust prevalence estimates across all organ systems and identifying rare manifestations with important clinical implications. These findings will facilitate earlier diagnosis, inform monitoring strategies, and guide future research priorities.

Abstract P1-08-24: The diagnosis of Anti-Yo antibody mediated paraneoplastic syndrome, a rare neurodegenerative disorder in a patient with invasive breast cancer, a case report

Abstract Abstract: Background: Paraneoplastic cerebellar degeneration (PCD), also known as Anti-Yo antibody syndrome, is a rare neurodegenerative manifestation described in patients with malignant tumors, including breast cancer. In these patients, the diagnosis of breast cancer usually follows the onset of neurologic symptoms and can be made months to years after symptom onset, most commonly through PET scan or CT whole body scans. Case presentation: We present the case of a 51-year-old female undergoing neurologic work up for suspected multiple sclerosis (MS) after experiencing sudden onset severe neurologic deficits to include diplopia, dysarthria, gait instability, and extremity paresthesias. As part of her evaluation, CT chest was obtained which revealed an incidental left breast mass. Diagnostic mammogram and subsequent core needle biopsy lead to the diagnosis of an ER/PR negative, HER2 positive invasive ductal carcinoma (IDC). During this time her neurologic symptoms were not responding to MS treatment regimens and further imaging was inconsistent with MS. In the setting of a newly confirmed breast malignancy, she underwent work up for a paraneoplastic syndrome to include PCA1/Anti-Yo antibodies. She was found to have significantly elevated levels of PCA1 (anti-Yo antibodies) consistent with PCD. She underwent neoadjuvant chemotherapy with TCHP, followed by partial mastectomy with sentinel lymph node biopsy, with minimal improvement in her neurologic symptoms. Surgical pathology revealed no evidence of residual IDC, negative margins, and no evidence of axillary metastasis – ypT0N0. To date she has completed adjuvant radiation therapy and remains on adjuvant Herceptin and Perjeta. Unfortunately, the patient’s symptoms have persisted despite breast cancer treatment. She has additionally undergone four cycles of plasmapheresis and IVIG treatments, with no significant improvement noted to date. Conclusions: Anti-Yo antibodies detected at significantly elevated levels causing a paraneoplastic syndrome of the brain is a rare manifestation and a very uncommon complication of breast cancer. The elevation of Anti-Yo antibodies has been observed in only 1.6% of breast cancer cases, with few documented instances of associated neurologic symptoms. This patient is one of the few rare cases to manifest this neoplastic syndrome and develop severe neurologic symptoms. While an uncommon complication of breast cancer, providers should consider investigating PCD in patients presenting with new-onset neurologic degenerative symptoms alongside a recent breast cancer diagnosis. Additionally, it has also been reported that over-expression of HER2 is frequently seen in patients with elevated levels of PCA1/Anti-Yo antibodies, as in our case. Citation Format: Ashley Montgomery, Ismail Jatoi, Carissia Calvo-Strube. The diagnosis of Anti-Yo antibody mediated paraneoplastic syndrome, a rare neurodegenerative disorder in a patient with invasive breast cancer, a case report [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2024; 2024 Dec 10-13; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2025;31(12 Suppl):Abstract nr P1-08-24.