A 28-year-old male musical student has been presented with visible inability of active abduction and extension of the thumbs in both hands beyond the neutral position. The student has not been previously diagnosed and claimed no history of trauma or surgical procedures in the area of hands and no family history of such disabilities. The student remained capable of playing on keyboard instruments on high level due to compensation by hyperextension of the interphalangeal joint of both thumbs and showed no increased frequency of the injuries or playing-related disorders. The ultrasound and magnetic resonance imaging showed complete bilateral agenesis of extensor pollicis brevis muscles and was classified as isolated congenital clasped thumb syndrome. Due to the age of the student and the agenesis of the muscles the conservative treatment was deemed inadequate and due to high functionality of the student as a musician and unforeseeable results it might have on a musician's career, surgical treatment has been disadvised.
Keywords: agenesis; clasped thumb; extensor pollicis brevis; hand; musician.