21/2/96

Dear Colleague:

Some months ago I was challenged by a family with a distinct autosomal dominant cerebellar ataxia associated with visual failure secondary to retinal pigmentary changes. Ages of onset and clinical course were variable(visual failure was not a feature in some patients of this family), but ataxia was a constant feature. Transmission of the disease to severe, infantile-onset cases occured in two siblings and both had a severe course, dying during adolescence.The ophthalmological examination always disclosed retinitis pigmentosa in those who are blind. Almost all of the affected adult patients in this family have already died. One affected young lady is living in the US but I do not know specifically where she is receiving medical care. One affected male living in Rio de Janeiro, now aged 27 is completely blind and has hyperactive tendon reflexes and some other severe neurological features besides ataxia.His intellect is apparently normal. His mother was blind and ataxic and died from the progressive disease about two years ago. Two married and apparently "healthy" brothers at ages 32 and 35 want desperately a presymptomatic diagnosis since they are planning to have children. I searched the literature and found a report from Enevoldson et al (Brain > 117:445-60, 1994) on 54 members of eight families in England, who presented with features similar to those here described. As far as I know, the gene mutation of this type of ataxia and blindness is still unknown and there is a possibility that like other types, it may consist of an unstable trinucleotide repeat expansion.The report of Gouw et al. (Neurology, 44:1441-7, 1994 is also pertinent and they have done linkage analysis to both SCA1 and SCA2. We plan to report this family as soon as possible.I would value comments of anyone with some clinical and genetic experience with a similar > family.Would anyone doing research in the area of molecular neurogenetics be interested in getting a blood sample from the above mentioned patient with the purpose of studying the gene mutation?