Concurrent Cold Autoimmune Hemolytic Anemia, Painless Thyroiditis, and Deep Vein Thrombosis Following Mycoplasma pneumoniae Pneumonia: A Rare Case of Multi-Organ Immune Complications.

A 22-year-old woman developed palpitations, fatigue, and right leg pain 18 days after suffering from Mycoplasma pneumoniae (MP) pneumonia. Laboratory tests revealed severe hemolytic anemia with elevated lactate dehydrogenase levels, a C3b/C3d-positive direct antiglobulin test, and high cold agglutinin titers, confirming cold autoimmune hemolytic anemia. Thyroid studies showed asymptomatic thyrotoxicosis without tenderness, which was consistent with painless thyroiditis. Venous ultrasonography revealed deep vein thrombosis in the right popliteal and soleal veins. She improved with cold avoidance and apixaban treatment. This case underscores that multi-organ immune complications can emerge during the subacute phase of an MP infection.