Metastatic melanoma presenting with paraneoplastic dermatomyositis mimicking polymyalgia rheumatica.

Authors

Srikanth Akunuri, Stella Bowcock, Ashir Iqbal, Jesal Doshi

Published in

BMJ case reports. Volume 19. Issue 9. Sep 30, 2026. Epub Sep 30, 2026.

Abstract

A man in his late 70s presented with 6-week bilateral shoulder and hip girdle pain, morning stiffness and significant weight loss. Although polymyalgia rheumatica was initially suspected, red flag weight loss prompted referral through the 2 week-wait cancer pathway with parallel laboratory and imaging assessment.Markedly elevated creatine kinase (>5000 U/L), proximal weakness and subtle cutaneous features raised suspicion of dermatomyositis. A CT scan then demonstrated extensive intra-abdominal and right inguinal lymphadenopathy, initially suggesting lymphoma and prompting haematology referral. Ultrasound-guided lymph node biopsy unexpectedly confirmed metastatic melanoma.Subsequent skin and nail examination identified a pigmented right great toe lesion, previously attributed to trauma, consistent with the primary acral melanoma. The overall picture was paraneoplastic dermatomyositis presenting as a polymyalgia-like syndrome. Corticosteroids and B-Raf proto-oncogene, serine/threonine kinase (BRAF)/mitogen-activated protein kinase (MEK) targeted therapy were followed by resolution of muscle symptoms and radiological response.

PMID:
42816108
Bibliographic data and abstract were imported from PubMed on 01 Oct 2026.

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