Bilateral congenital absence of the abductor pollicis brevis muscle: a case report.

Congenital absence of the abductor pollicis brevis is a very rare condition and is usually associated with other congenital anomalies. Here we report a case of bilateral congenital absence of the abductor pollicis brevis without any other abnormalities, which has not been previously reported. A 24-year-old Caucasian male patient presented to our clinic with flattening in the palmar region, pain and discomfort in writing, and weakness in both hands. USG and MRI revealed bilateral absence of the abductor pollicis brevis muscle. Bilateral congenital absence of the abductor pollicis brevis muscle requires no treatment due to satisfactory hand function, and results in cosmetic problems. Congenital absence of the abductor pollicis brevis muscle should be kept in mind in patients with flattening of the thenar eminences.