Inclusion body myositis (IBM)

Clinical, histological, immunohistochemical and ultrastructural features of 5 cases of inclusion body myositis -4 sporadic (s-IBM) and one hereditary (h-IBM) form are described. These patients (3 men, 2 women) had chronic progressive weakness of varying severity in all 4 extremities with sparing of cranial muscles. Elevation of CPK was noted in 2 patients. Electromyography revealed features of myopathy in 4 and additional neurogenic changes in 2 subjects. Clinical diagnosis was often other than inclusion body myositis. Presence of characteristic eosinophilic inclusions within the vacuoles established the diagnosis. The inclusions were congophilic and showed positivity to ubiquitin, beta-amyloid and SMI-31 in the sporadic cases while congophila was absent in the hereditary form. Immunostaining to hyperphosphorylated-tau was negative in both s-IBM and h-IBM. Membraneous whorls were observed at ultrastructural level. None of the patients improved with steroids and trial with other immunosuppressants was unsuccessful.