A 13 year-old female with an 11-month history of type 1 diabetes mellitus (DM) was admitted to the hospital with a muscle infarction. Diagnosis of this rare complication of DM was suggested by clinical presentation, magnetic resonance imaging (MRI) and muscle biopsy. While diabetic muscle infarction (DMI) has been previously described in adult patients with long-standing DM associated with microangiopathy, it is an unexpected finding in this clinical setting.