DermatologyTier 2Disease (DEADMAN)

Cutaneous manifestations of systemic disease - dermatomyositis

Description

Dermatomyositis produces characteristic, often diagnostic cutaneous findings - heliotrope rash and Gottron's papules are pathognomonic - reflecting complement-mediated microvascular injury targeting skin alongside the proximal muscle weakness seen in the systemic disease (see dermatomyositis under myopathies for the full disease detail)

Skin findings can precede, accompany, or (in amyopathic dermatomyositis) occur entirely without significant muscle involvement - a recognised, important variant given its own distinct malignancy-association implications

The same complement-mediated microvascular injury process affecting muscle in dermatomyositis also targets cutaneous small vessels, producing a distinctive photosensitive, vasculopathic rash pattern

Heliotrope rash - a violaceous discoloration of the upper eyelids, often with periorbital oedema; Gottron's papules - violaceous, scaly papules over the extensor surfaces of the MCP/PIP/DIP joints (distinguishing them from the more diffuse "Gottron's sign" seen over other extensor surfaces such as elbows/knees); "shawl sign" (photosensitive erythema over the upper back/shoulders) and "V-sign" (similar distribution on the anterior chest) are also characteristic
Nailfold capillary changes (dilated, dropped-out capillary loops, visible on capillaroscopy or sometimes with the naked eye) are a supportive finding shared with other connective tissue diseases
Amyopathic dermatomyositis (skin findings without significant clinical muscle weakness) still carries the same malignancy association and can still progress to develop muscle involvement or interstitial lung disease over time

Skin-directed therapy (photoprotection given the photosensitive component, topical corticosteroids, hydroxychloroquine) for cutaneous-predominant disease
Systemic immunosuppression as per the classic dermatomyositis approach (corticosteroids + steroid-sparing agent) when muscle or other organ involvement is present
Malignancy screening (age-appropriate, given dermatomyositis's recognised paraneoplastic association) is a key management step regardless of whether myopathy is present

Malignancy association (particularly in older-onset dermatomyositis), interstitial lung disease (particularly with certain myositis-specific antibodies), polymyositis (the key differential lacking the characteristic skin findings)

Amyopathic dermatomyositis (skin findings alone, no significant muscle weakness) still carries the same malignancy association as classic dermatomyositis and requires the same screening - a frequently tested point, since the absence of myopathy might otherwise be mistakenly reassuring

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