Melorheostosis and Osteopoikilosis: A Review of Clinical Features and Pathogenesis.

Melorheostosis is an exceptionally rare sclerosing hyperostosis that typically affects the appendicular skeleton in a limited segmental fashion. It occasionally occurs on a background of another benign generalised sclerosing bone condition, known as osteopoikilosis caused by germline mutations in LEMD3, encoding the inner nuclear membrane protein MAN1, which modulates TGFß/bone morphogenetic protein signalling. Recent studies of melorheostosis lesional tissue indicate that most cases arise from somatic MAP2K1 mutations although a small number may arise from other genes in related pathways, such as KRAS. Those cases associated with MAP2K1 mutations are more likely to have the classic "dripping candle wax" appearance on radiographs. The relationship between these somatic mutations and those found in a variety of malignant conditions is discussed. There are also similar germline mutations involved in a group of genetic disorders known as the RASopathies (including Noonan syndrome, Costello syndrome and various cardiofaciocutaneous syndromes), successful treatments for which could be applied to melorheostosis. The diagnosis and management of melorheostosis are discussed; there are 4 distinct radiographic patterns of melorheostosis and substantial overlap with mixed sclerosing bone dysplasia. Medical treatments include bisphosphonates, but definitive guidance on their use is lacking given the small number of patients that have been studied. Surgical intervention may be required for those with large bone growths, nerve entrapments, joint impingement syndromes or major limb deformities. Bone regrowth is uncommon after surgery, but recurrent contractures represent a major issue in those with extensive associated soft tissue involvement.

Pharmacotherapy of vasculitis.

The systemic vasculitides are characterized by inflammatory lesions in blood vessels. Therapeutic approaches should be based on the aetiology or pathophysiology of disease. Unfortunately, for many of these disorders neither is fully understood and empirical treatment based on clinical presentation and the pattern of organ involvement is used. This approach is effective in improving survival in the most serious forms. We undertook a systematic literature review to assess the evidence for using drug therapies in vasculitis. Glucocorticoids remain essential for many forms of vasculitis; indeed, in giant-cell arteritis, they may be the only therapy necessary. However, additional immunosuppressive agents are required for other forms of vasculitis: methotrexate in Takayasu's arteritis and non-renal small-vessel vasculitis and cyclophosphamide for classic Wegener's granulomatosis, microscopic polyangiitis, polyarteritis nodosa and Churg-Strauss syndrome with poor prognostic features. Subsequent disease control is with low-dose glucocorticoid and azathioprine or methotrexate. Biologic therapy is being used in resistant cases. Patients experience significant short- to medium-term toxicity, especially infection and steroid side effects. Late sequelae due to high cumulative doses of cyclophosphamide include infertility and malignancy. Such risks are being reduced due to more judicious use of short courses of cyclophosphamide followed by substitution by safer agents.