Discoid lupus erythematosus

Discoid lupus erythematosus is a benign disorder generally seen in younger females, particularly people with darker skin pigmentation. It very rarely progresses to systemic lupus erythematosus (in less than 5% of cases). Discoid lupus erythematosus is characterised by follicular keratin plugs and is thought to be autoimmune in aetiology.

Features

• erythematous, raised rash, sometimes scaly
• may be photosensitive
• more common on face, neck, ears and scalp
• lesions heal with atrophy, scarring (may cause scarring alopecia), and pigmentation
• serology
  • typically has negative or low-titre ANA, and anti-dsDNA / anti-Sm are usually absent
  • this helps explain how progression to SLE is uncommon

Discoid lupus erythematous affecting the scalp

Management

• topical steroid cream
• oral antimalarials may be used second-line e.g. hydroxychloroquine
• avoid sun exposure and smoking
  • smoking increases disease severity and reduces response to antimalarials

Drug-induced lupus

In drug-induced lupus not all the typical features of systemic lupus erythematosus are seen, with renal and nervous system involvement being unusual. It typically resolves after the trigger drug is stopped; the latent period can be long (≈1 month to >10 years), making causality easy to miss. Drug-induced SCLE can be clinically/serologically indistinguishable from idiopathic SCLE

Features

• arthralgia
• myalgia
• skin (e.g. malar rash) and pulmonary involvement (e.g. pleurisy) are common