This report describes a rare, congenital hypertrophy of the left upper extremity that appeared after compressive bandage of right arm at the age of two. He is eighteen years old, and hypertrophy was aggravated for about 2 years since he started weight training exercise. Recently, skin turgor changed and he visited the Dermatology department. Skin biopsy revealed increased thickness of the dermis. On Orthopaedic examination, the left arm showed nonspecific neuro-muscular changes other than easy fatigability a.nd increased skin consistency after exercise, compared to the right arm. The differences of circumference were 2.5 to 4cm according to the level of the upper limb. But the relative proportion of hypertrophy of the limb was balanced., On X-ray examination, bony changes were not shown. Through the MRI, we could find edematous changes of subcutaneous fatty tissue. Muscular structures showed unremarkable changes. Through the endurance test of both arms, we could find a decrease in endurance of the left upper arm musculatures. On histologic examination, infrequent focal necrosis and peri fascicular degeneration of the muscle fiber were present.
