A 28-year-old woman with biopsy-proven lupus nephritis (Class IV) is being evaluated for extra-renal manifestations of SLE. Which of the following is NOT a typical feature of SLE?

Explanation

## Cutaneous Manifestations of SLE — Distinguishing Features **Key Point:** While SLE has multiple cutaneous manifestations, erythematous nodules with central ulceration on extensor surfaces are characteristic of **erythema nodosum**, which is NOT a typical SLE skin finding. Erythema nodosum is associated with sarcoidosis, tuberculosis, streptococcal infection, and inflammatory bowel disease — not SLE. ### Typical SLE Skin Lesions | Lesion Type | Characteristics | SLE Association | | --- | --- | --- | | **Malar (butterfly) rash** | Erythema over cheeks and bridge of nose, classically spares nasolabial folds | Hallmark; acute or chronic | | **Discoid rash** | Erythematous plaques with follicular plugging, central atrophy, scarring | Chronic cutaneous SLE; may occur without systemic disease | | **Photosensitive rash** | Exacerbation of lesions on sun-exposed areas | Present in ~40–60% of SLE patients | | **Subacute cutaneous SLE (SCLE)** | Non-scarring, annular or papulosquamous lesions on trunk/arms | Associated with anti-Ro/SSA antibodies | | **Erythema nodosum** | Tender nodules on shins/legs with central ulceration | NOT typical of SLE; associated with sarcoidosis, TB, IBD | **High-Yield:** The **ACR/EULAR 2019 classification criteria** for SLE include malar rash, discoid rash, and photosensitivity as skin manifestations, but erythema nodosum is explicitly excluded. **Clinical Pearl:** Patients with discoid lesions may develop systemic SLE later; conversely, systemic SLE patients may have discoid lesions. However, pure discoid lupus (without systemic features) is a distinct entity. ### Why Erythema Nodosum is Not SLE 1. **Histopathology:** Erythema nodosum shows septal panniculitis; SLE skin lesions show interface dermatitis and vacuolar degeneration. 2. **Clinical context:** Erythema nodosum is tender, nodular, and typically on lower extremities; SLE rashes are usually non-tender and on face/upper trunk. 3. **Immunology:** Erythema nodosum is not associated with ANA or anti-dsDNA antibodies. [cite:Harrison 21e Ch 297]