ACUTE LYMPHOCYTIC INFILTRATION IN AN EXTREMELY EARLY LESION OF FIBRODYSPLASIA OSSIFICANS PROGRESSIVA

A 2-year-old child with fibrodysplasia ossificans progressiva underwen t a muscle biopsy of a very early lesion, and had findings that showed the earliest stage ever seen in the histopathology of fibrodysplasia ossificans progressiva. This very early stage consisted of intense per ivascular lymphocytic infiltration into normal appearing skeletal musc le. A nearly identical histopathologic sequence was noted in a cat wit h phenotypic features similar to those of fibrodysplasia ossificans pr ogressiva in humans. These new findings represent the earliest documen ted changes that have ever been noted in fibrodysplasia ossificans pro gressiva, and provide further histopathologic support for the recent d iscovery that lymphocytes may play a role in the pathogenesis of heter otopic ossification in fibrodysplasia ossificans progressiva.