Von Hippel-Lindau disease associated with myasthenia gravis not related to thymoma

BACKGROUND Von Hippel-Lindau disease (VHL) is a rare autosomal dominant inherited disorder characterized by an increased risk of tumours in a number of locations (eyes, brain, adrenal gland, pancreas, liver, kidneys, or other areas of the body). It is caused by germline mutation in the VHL gene. The VHL gene is a tumour suppressor gene that has been identified on the short arm of chromosome 3.
CASE REPORT We report a case of a 60 year-old female with the clinical diagnosis of VHL type 1 (cerebellar haemangioblastoma, pancreatic cysts with subsequent steatorrhoea, and bilateral renal carcinoma) who developed weakness and fatigability of skeletal muscles, left lid ptosis, snarling expression and nasal timbre speech. Acetylcholine receptor antibodies were negative in serum, while the electrodiagnostic test demonstrated an alteration of neuromuscolar junction which was consistent with the diagnosis of myasthenia gravis. Contrast-enhanced TC scan of the anterior mediastinum was performed, which excluded thymus enlargement. VHL gene evaluation in this patient identified a new mutation (c279delC9) and polymorphism c291C>G. At present the patient still suffers from ataxia and dysmetria due to cerebellar involvement in VHL, while fatigue and lid ptosis improved after the treatment with oral pyridostigmine 60 mg tid.
DISCUSSION AND CONCLUSIONS To our knowledge this is the first report of a case of VHL associated with myasthenia gravis without thymoma. A case of VHL associated with a form of myasthenia gravis related to thymoma has been recently reported. In our case the absence of acetylcholine receptor antibodies may suggest a genetic origin also for the myasthenia gravis.