Lipodystrophies are a group of diseases characterized by loss of fat tissue and are associated with insulin resistance. A six-year-old girl followed with the diagnosis of autoimmune hepatitis showed a severe loss of fat tissue, hyperinsulinemia, impaired glucose tolerance, hypertriglyceridemia and low serum complement 4 (C4) levels. She had coarse facial features with generalized loss of subcutaneous fat and prominent muscularity. Remarkable acanthosis nigricans was present over the neck, axilla, and umbilicus. Two hours after glucose loading, the glucose tolerance test revealed a glucose level of 258 mg/dL, a HbA1c value of 6.8%, and an insulin level of 642.9 mIU/mL, documenting a state of insulin resistance and type 2 diabetes mellitus. Acquired generalized lipodystrophy was diagnosed and metformin with dietary intervention was initiated. Low serum complement levels proved the autoimmune nature of the process. We conclude that the serum complement levels must be investigated in patients with acquired lipodystrophy, particularly when it is associated with autoimmune hepatitis.