A 28-year-old woman with a 6-month history of photosensitive facial erythema presents to the dermatology clinic. Examination reveals a symmetric erythematous rash over the cheeks and bridge of the nose in a butterfly distribution. The area marked **C** in the diagram (nasolabial folds) is notably spared. Laboratory investigations show ANA 1:320, anti-dsDNA positive, and low C3 levels. Which of the following diagnoses is most strongly supported by the sparing of the nasolabial folds as a distinguishing feature?

Explanation

## Why Systemic Lupus Erythematosus with malar rash is right The sparing of the nasolabial folds (marked **C**) is a classic and distinguishing histopathologic and clinical feature of the malar rash of SLE. This finding, combined with the photosensitive butterfly distribution across the nasal bridge, ANA positivity, anti-dsDNA positivity, and complement reduction, fulfills the 2019 EULAR/ACR SLE classification criteria. The malar rash is one of the weighted clinical criteria in the classification system, and its characteristic sparing of the nasolabial folds helps differentiate it from other facial erythematous conditions. Hydroxychloroquine is the first-line agent for all SLE patients, including those with cutaneous manifestations. ## Why each distractor is wrong - **Rosacea with telangiectasia and pustules**: Rosacea characteristically *involves* the nasolabial folds and features telangiectasias, pustules, and papules. The sparing of nasolabial folds is NOT a feature of rosacea, making this diagnosis incompatible with the clinical presentation described. - **Seborrheic dermatitis with greasy scales**: Seborrheic dermatitis is a common inflammatory condition that typically *affects* the nasolabial folds, presenting with greasy, yellowish scales. The sparing of nasolabial folds is not characteristic of this condition. - **Acute cutaneous lupus erythematosus (ACLE) without systemic involvement**: While ACLE does present with the malar rash and sparing of nasolabial folds, the presence of anti-dsDNA positivity, low complement levels, and systemic ANA elevation indicates systemic involvement and meets criteria for SLE rather than isolated cutaneous disease. **High-Yield:** The sparing of nasolabial folds in a photosensitive butterfly rash is pathognomonic for SLE malar rash and helps distinguish it from rosacea and seborrheic dermatitis, which involve the nasolabial folds. [cite: Robbins 10e Ch 6; Harrison 21e Ch 360; 2019 EULAR/ACR SLE Classification Criteria]