Paraneoplastic dermatomyositis
Cancer-associated dermatomyositis; "malignancy-associated DM"; the paraneoplastic subgroup within the broader spectrum of idiopathic inflammatory myopathies
Dermatomyositis (DM) is an autoimmune inflammatory myopathy with characteristic cutaneous features β the heliotrope rash, Gottron papules and Gottron sign, the V sign, the shawl sign, holster sign and mechanic's hands β accompanied by symmetrical proximal muscle weakness and a wide range of pulmonary, cardiac and gastrointestinal complications. The skin-oncology importance lies in the substantially elevated cancer risk in adult-onset DM: in pooled studies, ~15β30% of adults with DM have an underlying or subsequently diagnosed malignancy, with a relative risk of ~6β8 over the general population. The risk is markedly higher in older patients (>50), male sex, certain myositis-specific autoantibodies (especially anti-TIF1-Ξ³), severe cutaneous disease and refractory myopathy. The classical malignancies are ovarian, lung, breast, colorectal and gastric carcinomas in Western populations, with nasopharyngeal carcinoma over-represented in East Asian populations. Comprehensive cancer screening at DM diagnosis and during the subsequent 3 years is now standard practice; the IMACS 2023 (Oldroyd et al., Nat Rev Rheumatol 2023) guidelines provide a structured approach.
Cutaneous features
- Heliotrope rash β violaceous discolouration of the upper eyelids Β± periorbital oedema; pathognomonic.
- Gottron papules β violaceous flat-topped papules over the dorsal MCP, PIP and DIP joints; pathognomonic.
- Gottron sign β symmetric violaceous macules over the extensor surfaces of elbows, knees, malleoli (without papules).
- V sign β V-shaped photo-distributed erythema on the upper anterior chest.
- Shawl sign β erythema across the upper back and shoulders.
- Holster sign β erythema on the lateral hips / thighs.
- Mechanic's hands β hyperkeratotic fissured skin on lateral fingers and palms; particularly with anti-synthetase syndrome.
- Periungual telangiectasia with cuticular hypertrophy ("ragged cuticles").
- Calcinosis cutis β particularly in juvenile DM but also adult.
- Diffuse poikiloderma in chronic disease.
- Severe pruritus is common.
Cancer risk in adult-onset DM
- ~15β30% of adults with DM have an associated malignancy (at diagnosis or within ~3 years).
- Relative risk ~6β8 over the general population.
- Risk highest in:
- Older patients (>50).
- Male sex.
- Anti-TIF1-Ξ³ antibody positive β strongest single autoantibody marker (~70% of TIF1-Ξ³-positive adults have an underlying cancer at diagnosis or within 3 years).
- Anti-NXP-2 antibody β second strongest autoantibody marker (especially in men).
- Severe cutaneous disease.
- Refractory myopathy.
- Rapid onset.
- Skin necrosis.
- Dysphagia (oesophageal) β also a sign of severe DM.
- The risk is concentrated in the 3 years before and after DM diagnosis.
- Common underlying malignancies (Western populations):
- Ovarian (women) β over-represented.
- Lung.
- Breast.
- Colorectal.
- Gastric.
- Pancreatic.
- Non-Hodgkin lymphoma.
- East Asian populations β nasopharyngeal carcinoma (NPC) is the dominant association.
Cancer screening β IMACS 2023 (Oldroyd et al., Nat Rev Rheumatol 2023) guidelines
- Risk-stratified approach based on autoantibody status, age, sex and risk factors.
- Standard initial screen for all adults with new DM:
- Full history and examination.
- FBC, U&E, LFT, calcium, ESR / CRP.
- Urinalysis.
- Stool occult blood test / FIT.
- Tumour markers β SCC antigen, CEA, CA19-9, CA15-3, CA125, AFP, PSA (guided by symptoms / sex).
- Mammography (women); cervical screening up to date.
- CT chest, abdomen, pelvis.
- Pelvic MRI (women) β particularly important for ovarian carcinoma.
- Upper GI endoscopy and colonoscopy in selected patients.
- Nasopharyngoscopy in East Asian patients.
- Whole-body PET-CT β increasingly used as a comprehensive single-test approach.
- Repeat screening at 6, 12, 24 and 36 months in high-risk patients (anti-TIF1-Ξ³-positive, refractory disease, >50 years).
- Refer to a rheumatology / connective tissue MDT.
Management
- Treat the underlying malignancy β DM frequently improves with successful cancer treatment and may relapse with cancer recurrence.
- Immunosuppression for the DM:
- High-dose oral corticosteroid (prednisolone 1 mg/kg/day with slow taper).
- Methotrexate or azathioprine β first-line steroid-sparing.
- IVIg, mycophenolate, ciclosporin, tacrolimus β second-line.
- Rituximab for refractory disease.
- JAK inhibitors (tofacitinib, baricitinib) β emerging.
- Photoprotection β DM eruption is photosensitive.
- Topical corticosteroid / calcineurin inhibitor for skin disease.
- Hydroxychloroquine for cutaneous DM.
- Anti-pruritic measures β antihistamines, gabapentin / pregabalin.
- Calcinosis cutis β challenging; topical sodium thiosulfate, surgical excision.
- Refer to rheumatology, dermatology, respiratory medicine, oncology MDTs.
References
- Oldroyd AGS et al. International Guideline for Idiopathic Inflammatory Myopathy-associated Cancer Screening β IMACS / ENMC. Nat Rev Rheumatol; 2023.
- Trallero-AraguΓ‘s E et al. Cancer-associated myositis and antitif1Ξ³ antibody β review. Arthritis Rheum; 2012.
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