Asymmetric darkened knuckles with subclinical myopathy revealed anti-Mi2b positive dermatomyositis

Excerpt

A 25-year-old female presented to the Rheumatology outpatient department with 1-year history of fatigue, arthralgia, and skin hyperpigmentation. She noticed a gradually progressing darker tone in her skin with significant blackish pigmentation of the knuckles for 6 months. She also complained of occasional myalgia and difficulty in getting up from the bed. On examination, she had blackish pigmentation on left finger knuckles and skin of fingertips. Her skin complexion had a blackish hue. Motor examination revealed mild neck and truncal weakness (neck power by manual muscle testing 8 (MMT8) method = 7/10) with preserved motor power in upper and lower limbs (MMT8 for all groups of muscles 9/10). There were no tender joints at the time of examination. Other systemic examinations were unremarkable. There was a suspicion of clinically amyopathic dermatomyositis (CADM). Muscle enzymes were normal and routine blood reports were unremarkable. Myositis profile showed anti-Mi2b antibody was strongly positive. This was a case of anti-Mi2b antibody-positive CADM presented with pigmentary lesions on knuckles (Fig. 1).

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