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Chapter: Clinical Dermatology: Connective tissue disorders

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Mixed connective tissue disease

This is an overlap between SLE and either scleroderma or polymyositis.

Mixed connective tissue disease

This is an overlap between SLE and either scleroderma or polymyositis.

Presentation

As in LE, women are affected more often than men. Many develop swollen hands and sclerodactyly, and skin lesions like those of cutaneous LE may also be present. Alopecia is mild and the hair fall mimics telogen effluvium. Peri-ungual telangiectasia and pigmentary disturbances are common. About 25% of patients have a small vessel vasculitis with palpable purpura, leg ulcers and painful dermal nodules on the hands or elbows. Many show Raynaud’s phenomenon, arthritis, serositis and myositis. Headaches, weakness, fatigue, lymph node enlargement or hoarseness occur in about one in three patients; renal and central nervous system disease are less common.

Course

The disorder is chronic, and usually turns into either SLE or systemic sclerosis.

Differential diagnosis

The disorder can be confused with SLE, dermato-myositis, polymyositis, systemic sclerosis and other sclerosing processes such as porphyria cutanea tarda.

Investigations

Patients with mixed connective tissue disease have anti-bodies in high titre directed against one or more extract-able nuclear antigens. These give a speckled pattern when serum is reacted against nuclei and detected by indirect immunofluorescence. Direct immunofluores-cence of involved and uninvolved skin shows IgG within the epidermal nuclei, also in a speckled pat-tern. Only one-third of patients have subepidermal immunoglobulin deposits in involved skin. Most have hypergammaglobulinaemia, a high ESR, oesophageal dysmotility, abnormal pulmonary function tests and a positive rheumatoid factor. Hypocomplementaemia, leucopenia, anaemia, cryoglobulinaemia and false-positive biological tests for syphilis occur in a few patients. 

Treatment

Treatment depends upon which organs are involved, but systemic steroids are usually needed, in the same dosage as for SLE. Immunosuppressive agents reduce the dosage of systemic steroids, and NSAIDs help with arthralgia, myalgia and swelling of the hands.

 

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