Diagnostic Considerations for Myopathies with Hand Rash

Primary Diagnostic Consideration: Dermatomyositis

The American College of Rheumatology suggests that dermatomyositis is the primary diagnosis to consider when a patient presents with myopathy and hand rash, particularly when Gottron's papules or mechanic's hands are present 1
The presence of Gottron's papules, which are erythematous papules over the metacarpophalangeal and interphalangeal joints, is diagnostic of dermatomyositis, as stated by the European League Against Rheumatism 2, 3
Mechanic's hands, which are hyperkeratotic, cracked skin on the lateral and palmar aspects of fingers, are strongly associated with antisynthetase syndrome, according to the American College of Rheumatology 1

The American College of Rheumatology recommends considering antisynthetase syndrome in patients with hand rash, particularly those with mechanic's hands, and associated features such as Raynaud phenomenon, arthritis, interstitial lung disease, fever, and myositis 1
Anti-Jo-1 antibody is the most common antibody associated with antisynthetase syndrome, but other antibodies such as anti-PL-7, anti-PL-12, OJ, EJ, KS, Ha, and Zo may also be present, as stated by the European League Against Rheumatism 1

The American College of Rheumatology suggests identifying the hand rash pattern, determining the temporal relationship between rash and weakness, and performing laboratory evaluations, including measuring CK and myositis-specific antibodies, to diagnose myopathies with hand rash 1, 2, 4
The European League Against Rheumatism recommends confirming the diagnosis with muscle biopsy if the diagnosis is unclear, but notes that perifascicular atrophy is not specific for pure dermatomyositis 2, 3

The American College of Rheumatology recommends screening for malignancy in patients with pure dermatomyositis, particularly those with anti-p155/140 antibodies, due to the 21% cancer association, and suggests age-appropriate cancer screening plus CT chest/abdomen/pelvis 1, 5