summary Dysplasia Epiphysealis Hemimelica, also known as Trevor's Disease, is a rare congenital bone dysplasia caused by the development of an osteochondroma in the epiphysis that presents with asymmetrical limb deformity. Diagnosis is made with radiographs of the affected joint. Treatment is usually surgical excision of the lesion in early symptomatic disease. Epidemiology Incidence extremely rare estimated at ~ 1:1,000,000 Demographics recognised male predilection usually presents in young children Anatomic location most common in knee or ankle usually only involves one joint Etiology Pathophysiology caused by a defect in the Groove of Ranvier asymmetrical limb deformity due to localized overgrowth of cartilage Genetic non hereditary Presentation Symptoms asymmetrical limb deformity joint symptoms Physical exam decreased motion joint line tenderness Imaging Radiographs may see calcification at the joint line CT useful for assessing cortical continuity with the epiphysis Studies Histology similar to osteochondroma diagnosis of DEH is made with the location of the osteochondroma, specifically located in the epiphysis of the involved bone Treatment Operative excision of overgrowth indications symptomatic early disease osteotomies indications symptomatic late stage disease Complications Recurrence a common complication following excision Prognosis May lead to early osteoarthritis of affected joint