Autosomal dominant cerebellar ataxia: frequency analysis and clinical characterization of 45 families from Portugal.

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The relative frequency of the different autosomal dominant cerebellar ataxia (ADCA ) varies widely amongst different geographic locations . Here we describe a series of 45 ADCA families from Portugal .Patients with progressive cerebellar dysfunction of autosomal dominant transmission underwent a clinical examination protocol and genetic testing for spinocerebellar ataxia (SCA )1 to Machado-Joseph disease (MJD )/SCA 3 , SCA 6 , SCA 7 , SCA 10 , SCA 12 , SCA 17 and dentatorubral-pallidoluysian atrophy (DRPLA ). We registered the clinical characteristics and frequency of each type of ataxia .MJD /SCA 3 was the most frequent ADCA (26 families , 57 .8 % of all families ), followed by DRPLA (5 families , 11 .2 %), SCA 7 (2 families , 4 .4 %), SCA 2 and SCA 1 (1 family each , 2 .2 % each ); 10 families (22 .2 %) had no molecular diagnosis . SCA 1 and SCA 7 patients had African ancestry . DRPLA patients had Portuguese ancestry and were characterized by prominent anticipation and a variable combination of epilepsy , extra -pyramidal symptoms and dementia . Ophtalmoparesis , slow saccades and retinopathy were most distinctive of SCA 3 , SCA 2 and SCA 7 cases , respectively .MJD /SCA 3 was the most common ADCA in this group of families . The high frequency of DRPLA and presence of SCA 1 and SCA 7 cases was unexpected . The presence of these rarer ADCA types probably reflects migration phenomena , posing a challenge for differential diagnosis .