Mixed Connective Tissue Disease (MCTD) in a Girl with Lower Extremities Edema: A Brief Report

Mixed Connective Tissue Disease (MCTD) is a rare condition in children, characterized by a high titer of anti-ribonucleoprotein-U1 (anti-U1 RNP) antibodies, often presenting with overlapping features of two or more rheumatologic disorders, including juvenile idiopathic arthritis (JIA), systemic lupus erythematous (SLE), systemic sclerosis (SSc), and juvenile dermatomyositis/polymyositis (JDM/PM).

We report the case of an 8-year-old girl with a history of fever, hair loss, lower extremities edema, weakness, oral aphthous ulcers, and a high titer of anti-U1 RNP antibodies, which is consistent with the diagnosis of MCTD. The patient received immunomodulator drugs, and her disease went into remission.

Diagnosing MCTD in pediatric patients can be challenging. It should be considered especially in cases with recurrent muscular weakness or pain, lupus-like manifestations, and edema. Moreover, serum anti-U1 RNP testing can be a helpful diagnostic tool.