[Clinical diagnosis of the adult form of Niemann-Pick type C disease].

The adult form of Niemann-Pick type C disease displays specific phenotypic, biochemical and genetic features that differentiate it from the infantile and juvenile ones. This form is often linked to the variant biochemical phenotype with mild abnormalities of the filipin test that can make the diagnosis difficult. Visceral signs usually consist in an asymptomatic hepato splenomegaly which can be present since early childhood, remains poorly progressive, and may not be detected unless abdominal ultrasonography is performed. Psychiatric signs and cognitive troubles constitute the most frequent revealing symptoms in adults and can sometimes appear after 50 years. During the clinical course, main clinical features include vertical supranuclear gaze palsy, cerebellar ataxia, dysarthria, cognitive troubles and movement disorders. Because of these poorly specific signs at onset, the diagnosis is often delayed. Clinicians must know how to recognize mild vertical supranuclear gaze palsy, which is an almost constant and very specific feature. An early diagnosis is mandatory since the treatment seems more efficient when started early.