Paediatrics: Mixed connective tissue disease - overlap syndromes

Mixed connective tissue disease— overlap syndromes

Combined features of SLE, progressive systemic sclerosis, and dermato-myostis with positive ribonucleoprotein (RNP) antibody.

•   Prognosis and management similar to that of SLE , but more benign prognosis because renal and CNS involvement are rare.

Clinical features

•   Raynaud’s phenomenon (common).

•   Swollen hands and fingers (common).

•   Polyarthritis: symmetrical peripheral.

•   Rashes: similar to SLE or JDM rash; tight non-elastic skin of hands.

•   Muscle weakness and myositis.

•   Restrictive lung disease and pulmonary hypertension (rare).

Differential diagnosis

•   Systemic onset JIA.

•   RF-positive polyarticular JIA.

•   SLE.

Investigations

•   Characteristic anti-RNP antibody.

•   Other autoantibodies: ANA +ve (90%); RF +ve (often).

•   FBC: leucopenia; thrombocytopenia.

•   CXR.

·  Renal function.

Echocardiogram: screen for right ventricular hypertrophy secondary to pulmonary hypertension in established disease.