Dermatomyositis — SCE Dermatology MCQ

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HardGeneral dermatology & dermatology in primary health careDermatomyositisSCE Dermatology

A 59-year-old woman has violaceous erythema over the eyelids, scaly papules over the metacarpophalangeal joints and proximal muscle weakness. Creatine kinase is 1,480 IU/L, and she has dysphagia. What is the most important differential to exclude?

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Correct answer: A — Underlying malignancy associated with dermatomyositis

The correct answer is A, underlying malignancy associated with dermatomyositis. The heliotrope eyelid erythema, Gottron papules over the metacarpophalangeal joints, raised creatine kinase (1,480 IU/L) and dysphagia together confirm dermatomyositis, and adult onset disease carries a well-documented paraneoplastic association, with malignancy found in up to a quarter of cases, most commonly ovarian, lung, pancreatic, gastric, colorectal and lymphoma. Dysphagia here reflects oesophageal or pharyngeal muscle involvement, which itself is a marker of more severe, treatment-resistant disease and higher malignancy risk. Because occult cancer can predate, coincide with, or follow the skin and muscle findings, all newly diagnosed adult dermatomyositis patients require age-appropriate cancer screening (examination, CT chest/abdomen/pelvis, relevant tumour markers, and CA-125 or pelvic imaging in women) rather than dermatology or rheumatology treatment alone. Why the other options are wrong: E. Simple allergic eyelid dermatitis: this causes eczematous, itchy eyelid change without Gottron papules, myositis, raised CK, or dysphagia, so it does not fit the systemic features described. D. Rosacea with ocular involvement: produces facial erythema, telangiectasia and blepharitis/keratitis, not a heliotrope rash, and has no association with proximal weakness or elevated CK. C. Chronic plaque psoriasis: gives well-demarcated silvery plaques typically over extensor surfaces, not violaceous eyelid erythema, and does not cause myositis or dysphagia. B. Seborrhoeic dermatitis: causes greasy scaling in sebaceous areas (scalp, nasolabial folds), lacking the violaceous hue, Gottron papules, muscle enzyme rise, or swallowing difficulty seen here. Key point: Any adult with new dermatomyositis, especially with dysphagia or rapid onset, must undergo prompt malignancy screening because of the strong paraneoplastic association.

Reference: DermNet NZ, Dermatomyositis, 2023 update, https://dermnetnz.org/topics/dermatomyositis