[Postpolio late progressive muscular atrophy--clinical and epidemiologic analyses in 4 Japanese cases].

Four Japanese cases of postpolio progressive muscular atrophy (PPMA) of late onset were clinically studied to characterize their clinical features and discussed upon the epidemiologic viewpoint. Four male patients were included with mean age of 43.5 (30-59) years on examination, diagnosed as PPMA after the criteria by Alter (1982) and Dalakas (1986). All suffered from polio at age 10 month to 8 years (mean: 3y) between 1931 and 1957 with residual motor paresis in one limb or two. Twenty-eight to 55 (mean: 40.3) years later, subsequent muscle weakness and atrophy appeared in the limb seemingly unaffected by the initial polio attack. Marked fasciculations and occasional myalgias were noticed without sensory disturbance and bulbar as well as upper motor neuron signs. Laboratory examinations revealed moderate elevations of serum CK and protein content in SCF. No significant elevation of polio virus antibody titers was found in both serum and CSF. Electromyography showed neurogenic changes of various degrees by muscle tested. Muscle CT disclosed patchy distribution of atrophied muscles with fatty replacement in all extremities. Spinal cord MRI images were unremarkable. Scatters of small grouped atrophy and fiber type grouping were noticed on muscle biopsy specimens. These findings summarized in our cases are generally compatible with those of hereby reported PPMA cases. On reviewing the western literature and the great epidemic of polio around 1960 in Japan, an increasing number of patients with PPMA can be anticipated in near future; possibly in 10 years.