Bone dysplasia series. Melorheostosis: review and update.

Melorheostosis is a rare nongenetic developmental anomaly first described in 1922 by Léri and Joanny. Its etiology is unknown. Patients present at any age, and both sexes are affected equally. Onset is usually insidious, with deformity of the extremity, pain, limb stiffness and limitation of motion in the joints first manifesting in late childhood or early adolescence and progressing into adult life. The characteristic radiographic appearance consists of irregular hyperostotic changes of the cortex, generally on one side of the bone, resembling melted wax dripping down one side of a candle. This appearance gave the anomaly its name, which is taken from the Greek words for member (melos) and flow (rhein). There is usually a distinct demarcation between the affected and normal bone. Dense, sclerotic linear areas are seen mainly in the cortex but also extending into the cancellous bone. Melorheostosis affects mainly the long bones of the upper and lower limbs, but also the short bones of the hand and foot and, rarely, the axial skeleton. It may co-exist with osteopoikilosis and osteopathia striata as well as with tumours or malformations of blood vessels or lymphatics. Soft-tissue ossifications at the site of the joint are common. Bone scintigraphy is positive and shows moderately increased uptake of tracer. Computed tomography and magnetic resonance imaging can further characterize the lesion, but rarely contribute to the diagnosis. The forme fruste of melorheostosis may mimic other conditions such as myositis ossificans, osteoma and parosteal osteosarcoma. Treatment of this chronic and sometimes debilitating condition consists of surgical soft-tissue procedures and even, in very severe cases, amputation.