Common presentations of an uncommon disease: A report of two pediatric cases with mixed connective tissue disease

Abstract

Mixed connective tissue disease (MCTD) is one of the rarest connective tissue diseases. Incidence is around 2–3 cases per 100,000 people. The diagnosis is often difficult due to multiple diagnostic criteria and overlapping features with other connective tissue diseases such as systemic lupus erythematosus, systemic sclerosis, and juvenile idiopathic arthritis (JIA). An accurate diagnosis is important for proper treatment and follow-up. We report two pediatric cases, who initially presented with common diseases such as nephrotic syndrome and JIA, but later turned out to have MCTD after completing the workup. Both patients had strongly positive anti-U1-ribonucleoprotein (RNP) antibodies. The first patient had features of Raynaud’s phenomenon as supportive evidence of MCTD. The second patient had hand edema, aseptic meningitis, and myositis as the supporting evidence in addition to clinical features and strongly positive anti-U1-RNP antibodies. Both patients showed good improvement after proper treatment and are under our follow-up.