A 10-year-old girl with Down syndrome and alopecia areata was admitted with severe ketoacidosis. She had high blood glucose level: 615 mg/dL and her HbAlc level was 13.3 %. After the control of ketoacidosis and reduction of the plasma glucose level, we found low free T4 level and high TSH levels. Thyroid peroxidase antibodies titer was 1383 IU/mL and both gliadin and endomysial antibodies were negative. This was the first report of a child with Down syndrome showing type 1 diabetes combined with alopecia areata and autoimmune thyroid disease. © 2009 Dr. K C Chaudhuri Foundation.