De Quervain disease is caused by a stenosing tenosynovitis in the first dorsal compartment, and the main aetiology is extensor pollicis brevis (EPB) tenosynovitis. We encountered three cases in which EPB tenosynovitis was absent and abductor pollicis longus (APL) tenosynovitis was confirmed during operation. In the treatment of de Quervain disease, APL tenosynovitis should be paid as much attention as EPB tenosynovitis.