Late-onset hereditary ataxia with global thermoanalgesia and absence of fungiform papillae on the tongue in a Japanese family.

Two Japanese male siblings, aged 68 and 59 years, affected by late-onset progressive ataxia distinguished by extensive sensory and mild autonomic disturbances are described. They had global thermoanalgesia, positive Romberg signs, sensorineural deafness, canal paresis and ageusia. Their autonomic disturbances consisted of absence of overflow tears with usual stimuli, dysphagia, blood pressure and vasomotor instability, diarrhoea/constipation, and urinary frequency. Sensory nerve action potentials were completely absent, whereas motor conduction velocity was slightly reduced only in the lower extremities. Sural nerve biopsy on the younger brother demonstrated a marked loss of myelinated fibres and a reduction in the number of unmyelinated axons. Tongue histology revealed absence of fungiform papillae and taste buds. Autonomic function tests showed widespread but mild sympathetic and parasympathetic failures. Neuro-imaging studies revealed atrophy of the spinal cord, cerebellum, brainstem and corpus callosum, and enlargement of the lateral, third and fourth ventricles. These siblings represent a previously unrecognized variant of late-onset hereditary spinocerebellar degeneration with global thermoanalgesia and absence of fungiform papillae on the tongue.