Spinocerebellar ataxia type I (SCA1): Revised diagnosis of a familial multiple sclerosis

A 7-generation pedigree of a family residing in and originating from the region of the German Hart Mountains is presented. The index patient, now a 43-y old man, suffers from typical clinical signs of cerebellar ataxia, First symptoms were reported at the age of 30 years and were misdiagnosed as multiple sclerosis, because an elder sister was thought to be suffering from this disease. She died at the age of 45 years. Apart from this sister, pedigree analysis revealed that the mother (death at 50 years) and the maternal grandfather (death at 49 years) had also suffered from multiple sclerosis. Molecular genetic analysis of the ataxin-1 gene showed in the affected persons a normal CAG repeat and an expanded one. We have had to correct the diagnosis as SCA1 as a special form of ADCA. Further predictive molecular genetic investigations of the at-risk siblings revealed values of normal CAG repeats. On comparing the progression of the illness between the index patient and his affected sister, we suggest that it is less progressive in the former because of better coping.