[A new observation of cherry-red spot myoclonus syndrome (author's transl)].

A 24 year-old white male patient presents since 8 years progressive gait disturbances, myoclonic jerks and a decrease of eyesight. Clinical examination reveals features reminding of Ramsay Hunt dyssynergia cerebellaris myoclonica associated with cherry-red spots in the eyegrounds. The diagnosis of sialidosis is supported by the ultrastructural examination of skin-conjunctival biopsies and by the abnormal urinary excretion of sialyloligosaccharides. It is established by the demonstration of a deficiency of acid neuraminidase in leukocytes and cultured fibroblasts. The phenotypic spectrum of sialidosis is extremely wide; this case belongs to the cherry-red spot myoclonus syndrome (Rapin et al., 1978), also called sialidosis type 1 - normosomatic group (Lowden and O'Brien 1979).