Abstract

We describe the clinical features of the first UK family with the recently described autosomal dominant cerebellar ataxia, deafness and narcolepsy associated with mutations in exon 21 of the DNMT1 gene. Only four other families have been described Worldwide.

The proband presented at the age of 53 years with a ten year history of unsteadiness and episodes of emotionally induced cataplexy. A cerebellar syndrome with accompanying ptosis, myoclonus and mild long–tract signs were notable on examination.

The patient's father was said to have had epilepsy and deafness. Examination of two other of the patients siblings revealed two other affected individuals (aged 58 and 60 years) with similar clinical features but with varying degrees of additional cognitive disturbance and optic atrophy. In addition, investigation of two of the offspring of one of the affected siblings revealed problems with cataplexy from their 20s.

MR Imaging of the proband revealed mild generalised involutional changes, EEG interictal epileptiform discharges, multiple sleep latency testing, neurophysiology and a muscle biopsy were within normal limits. Imaging of the more clinically affected siblings revealed more substantial cortical changes.

Sequencing of exon 21 of the DNMT1 gene revealed the previously described Ala570Val mutation.