[Clinical features and genetic analysis of a patient with type 2 neurofibromatosis manifested as oculomotor nerve palsy].

OBJECTIVE:To report on a rare case of Neurofibromatosis type 2 (NF2) manifesting as oculomotor nerve palsy and explore its genetic basis. METHODS:A patient with NF2 who had presented at Beijing Ditan Hospital Affiliated to Capital Medical University on July 10, 2021 was selected as the study subject. Cranial and spinal cord magnetic resonance imaging (MRI) was carried out on the patient and his parents. Peripheral blood samples were collected and subjected to whole exome sequencing. Candidate variant was verified by Sanger sequencing. RESULTS:MRI revealed bilateral vestibular Schwannomas, bilateral cavernous sinus meningiomas, popliteal neurogenic tumors, and multiple subcutaneous nodules in the patient. DNA sequencing revealed that he has harbored a de novo nonsense variant of the NF2 gene, namely c.757A>T, which has replaced a codon (AAG) encoding lysine (K) at position 253 with a stop codon (TAG). This has resulted in removal of the Merlin protein encoded by the NF2 gene from position 253 onwards. The variant was not found in public databases. Bioinformatic analysis suggested that the corresponding amino acid is highly conserved. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), the variant was rated as pathogenic (PVS1+PS2+PM2_Supporting+PP3+PP4). CONCLUSION:The heterozygous nonsense variant c.757A>T (p.K253*) of the NF2 gene probably underlay the disease in this patient with an early onset, atypical but severe phenotype.