Race for the Case answers

Diagnose this new case by Haowei Han, DO, and Aysham Chaudry, DO

A 64-year-old woman presented to the dermatology clinic with a two-year history of a widespread rash involving the scalp and left ear. She reported associated joint pain but denied fevers, fatigue, weight loss, oral ulcers, photosensitivity, or Raynaud phenomenon. Social history is notable for cigarette smoking and lack of regular sunscreen use.

On physical examination, there were bilateral preauricular hyperpigmented, atrophic plaques. The parietal scalp demonstrated violaceous to hyperpigmented, atrophic plaques accompanied by alopecia.

Laboratory evaluation revealed a positive antinuclear antibody (ANA) with a speckled pattern at a titer of 1:160 and an elevated Sjögren’s syndrome-related antigen A (SS-A/Ro) antibody level of 3.6 (reference range: 0.0–0.9). Anti-double-stranded DNA (anti-dsDNA) and anti-Smith antibodies were negative. Complete blood count (CBC), comprehensive metabolic panel (CMP), and urinalysis (UA) were all within normal limits.

A 4-millimeter (4 mm) punch biopsy of the scalp revealed follicular plugging, perifollicular fibrosis, periadnexal lymphocytic inflammation, increased dermal mucin deposition, and pigment incontinence. Vacuolar interface changes were noted, along with increased thickness of the basement membrane zone.

1. Based on the clinical, histopathologic, and laboratory findings, what is the most likely diagnosis?

Answer: The most likely diagnosis is discoid lupus erythematosus (DLE), a chronic cutaneous lupus subtype characterized by scarring, atrophic plaques, and follicular plugging, most commonly affecting the scalp, face, and ears.

2. What is the likelihood that this condition will progress to systemic lupus erythematosus (SLE)?

Answer: The risk is low but not negligible. Approximately 5-20% of these patients eventually meet the classification criteria for SLE.

3. Which stain can be used to highlight the thickened basement membrane zone seen in this condition?

Answer: Periodic acid-Schiff (PAS) stain is used to highlight the thickened basement membrane zone, which is a common histologic feature in cutaneous lupus erythematosus.

4. What stain can be used to highlight the increase in mucin deposition?

Answer: Alcian blue stain (at pH 2.5) is used to detect increased dermal mucin, which is often seen in discoid lupus erythematosus and other connective tissue diseases. Toluidine blue and colloidal iron are also acceptable and effective.

5. Infants born to mothers with positive SS-A (Ro) antibodies are at increased risk for which condition characterized by congenital heart block, annular lesions, and thrombocytopenia?

Answer: They are at risk for neonatal lupus erythematosus (NLE). This condition is associated with maternal anti-SS-A (Ro) and/or anti-SS-B (La) antibodies crossing the placenta and can present with:

• Congenital heart block (often irreversible)

• Annular, erythematous cutaneous lesions commonly on the face

• Hematologic abnormalities such as thrombocytopenia