Figure 21a. Fatty overgrowth. Axial T1-weighted MR images of the pelvis and upper thighs (a) and the upper to middle thighs (b) in a patient aged 20 years show asymmetric muscle development in the thighs, asymmetric focal increase of fatty tissue in the right buttock (* in a), diffuse increase of fatty tissue in the left thigh, and focal accumulation of fat anterior to the left distal femur (arrow in b).