BIOTIN-RESPONSIVE BASAL GANGLIA DISEASE - A NOVEL ENTITY

We describe a novel, biotin-responsive basal ganglia disease in 10 pat ients, At onset, it appears as a subacute encephalopathy, with confusi on, dysarthria and dysphagia with occasional supranuclear facial nerve palsy or external ophthalmoplegia, and progresses to severe cogwheel rigidity, dystonia and quadriparesis, These symptoms disappear within a few days if biotin (5-10 mg/kg/day) is administered, and there are n o neurological sequelae, They reappear within 1 month if biotin is dis continued, Patients diagnosed late, or who have had repeated episodes, suffer from residual symptoms such as paraparesis, mild mental retard ation or dystonia, The numerous biochemical studies of intermediary me tabolism, like the autoimmune and toxicological studies, enzyme assays including biotinidase, carboxylase and lysosomal activities, and bact erial and viral studies were all normal, The aetiology may be related to a defect in the transporter of biotin across the blood-brain barrie r. The only consistent radiological abnormality was central necrosis o f the head of the caudate bilaterally and complete, or partial, involv ement of the putamen on brain MRI. This was present during the initial acute encephalopathy and remained unchanged during followup of 3-10 y ears, Although its aetiology is unknown, it is important to recognize this disease, since its symptoms may be reversed and the progression o f its clinical course prevented simply by providing biotin.