Anti-synthetase syndrome is the presence of inflammatory myositis and/or interstitial lung disease with the presence of antibodies directed against an aminoacyl transfer RNA synthetase. Some cases may go on to develop arthritis, Raynaud’s phenomenon and mechanic’s hands. This patient during the initial presentation only had evidence of myositis and interstitial lung disease. However, prior to the subsequent relapse of the disease she developed mechanic’s hands. In fact, the mechanic’s hands preceded the muscle symptoms by a few months.
15–25% of patients with anti-synthetase syndrome will have anti Jo-1 antibody positivity while several other antibodies have been described with its unique clinical phenotypes. The anti Jo-1 positive anti synthetase syndrome is associated with myositis, interstitial lung disease, non-erosive arthritis, Raynaud’s phenomenon and mechanic’s hands.
Pathogenesis of mechanic’s hands in the setting of anti-synthetase syndrome is not clear. Histologically there is marked hyperkeratosis, focal parakeratosis, psoriasiform acanthosis, and colloid bodies in the epidermis. These are similar to histological features of psoriasis. Similarities in the histological changes and the successful use of ustekinumab in refractory mechanic’s hands could mean a pathogenesis similar to psoriasis [1, 2].
While mechanic’s hands are described as part of the clinical manifestations, whether its presence can be utilized as a prodromic sign of disease relapse needs further evaluation. In our case, the patient was in remission when she developed mechanic’s hands. Myositis was in remission evident by absence of muscle pains, proximal muscle weakness and by normalization of CPK and ESR. From a respiratory standpoint, she had a cough without any shortness of breath at the time of initial diagnosis however clinically improved with immunosuppressive therapy. Though spirometry results are not readily available, she remained clinically and radiologically stable respiratory wise throughout the disease course.
Few months developing mechanic’s hands she did go on to develop proximal muscle pain, weakness and CPK elevation. Subsequent escalation of immunosuppressive therapy led to the resolution of the mechanic’s hands and improvement in muscle power and normalization of CPK levels.
Therefore, the chronology of events in this case is suggestive of mechanic’s hands being considered as a prodromic sign of disease relapse.
In one previously reported case, the appearance of mechanic’s hands had preceded the development of myositis and arthritis . In another case with anti Jo-1 positive anti-synthetase syndrome, mechanic’s hands preceded the development of respiratory manifestations . However, in contrast there is another reported case of anti Jo − 1 antibody positive anti-synthetase syndrome with mechanic’s hands which was refractory to conventional treatment while other systemic manifestations were under control for a period of 3 years. Though cutaneous manifestations were resistant to therapy, the continuation of immunosuppressive therapy including MMF and methotrexate could have prevented a systemic disease relapse in this particular case .
Therefore, while further evidence is required before any solid conclusion can be made, our patient’s clinical scenario adds to the current evidence that mechanic’s hands should be considered as a prodromic sign of disease relapse.