Even though 89% of the patients had a fasting urinary osmolality below 450 mosmol/kgH2O [i.e., far below the normative values of 805–867 mosmol/kgH2O (11) in a healthy population], the plasma ADH value was high in most of our patients with SCA. The gene discussed is AVP; the disease is autosomal dominant cerebellar ataxia.