Article Text
Abstract
Our patient first presented with progressive unsteadiness and slurred speech at the age of 67 years. The initial working diagnosis was progressive ataxia. There were minimal cerebellar changes on MRI head and extensive laboratory tests including common spinocerebellar ataxia screen was negative. He sub- sequently developed distal muscle wasting and weakness, and pathologically brisk reflexes, with normal CK levels. Motor neuron disease (MND) was then clinically suspected, however, further neurophysiologi- cal studies and a nerve biopsy revealed changes consistent with an axonal neuropathy. Generalised muscle wasting, bilateral scapular winging, eyelid ptosis and complex ophthalmoplegia were identified eight years after initial clinic review. The complex evolving neurological phenotype prompted a muscle biopsy to investigate for mitochondrial disease. Whilst some evidence of mitochondrial dysfunction was identified, the mitochondrial DNA maintenance nuclear gene panel was negative. He was enrolled to the 100k genome project which revealed a heterozygous KIF5A pathogenic variant. Mutations in KIF5A are associated with a wide phenotypic spectrum including CMT neuropathy, hereditary spastic paraplegia and MND-like syndrome. Our case highlights the diagnostic conundrum of evolving neurological mani- festations of KIF5A disease that demonstrates overlapping cardinal features with mitochondrial disease.