Case report of an antimelanoma differentiationassociated protein 5 antibody-associated amyopathic dermatomyositis

ABSTRACT

Autoantibodies against melanoma differentiation-associated protein 5 (MDA5) associated with dermatomyositis have recently been described in Asians with rapidly progressive respiratory disease. Here we report the case of a middle-aged white woman with anti-MDA5 antibody-associated amyopathic dermatomyositis with interstitial lung disease (ILD), which is stable with minimal immune suppression. A 55-year-old woman was referred to a virtual dermatology clinic during the COVID-19 pandemic suspected of having widespread eczema involving the chest, face, arm and hands on the background of atopy. On direct questioning, she admitted to having constitutional symptoms, exertional dyspnoea, joint pain and symptoms of proximal muscle weakness. On clinical suspicion of possible connective tissue disorder, she was urgently reviewed in the hospital, where she was found to have a photodistributed rash involving cutaneous ulceration and violaceous plaques. Hand examination showed mechanic's hand mimicking hand eczema, ragged nail cuticles and acute tenosynovitis in the left index finger. Her upper and lower limb muscle power was normal and respiratory examination revealed bi-basal fine end-expiratory crepitation. Her repeated biochemical, haematological and muscle enzymes remained normal. Skin biopsy taken from photosensitive rash over the wrist showed hypergranulosis, Civatte body formation, colloid bodies and dyskeratotic keratinocytes, in keeping with severe lichenoid eruption. Superficial dermis showed patchy red-cell extravasation, perivascular chronic infiltration, dermal oedema and serum on the surface, in keeping with ulceration secondary to severe inflammatory processes. There were no eosinophils and eccrine coils were free of inflammation, raising the suspicion of a drug eruption. Her antinuclear antibody and double-stranded DNA were repeatedly negative. Myositisspecific antibody panel was performed owing to a high clinical suspicion of photosensitive dermatoses, both clinically and histologically. Histology revealed positive anti-MDA5 antibodies;repeated positive testing confirmed this. Although lung function was normal, computed tomography revealed evidence of ILD. We made a diagnosis of anti-MDA5 antibodyassociated amyopathic dermatomyositis with ILD. Her malignancy screening was negative. The patient was started on lowdose prednisolone and hydroxychloroquine 200 mg twice daily, with topical steroid applications, which resulted in remarkable clinical improvement. Anti-MDA5 associated dermatomyositis has characteristic cutaneous lesions consisting of skin ulceration and tender palmar papules, mechanic's hands, inflammatory arthritis and rapidly progressive ILD, which is frequently fatal. Although our patient had ILD, she was relatively stable on minimal immunosuppression. It is important for clinicians to have an increased awareness of this disease as it could have a highly variable clinical presentation in the white population.