Subacute cutaneous lupus erythematosus mimicking psoriatic arthritis: a case report

Subacute cutaneous lupus erythematosus (SCLE) is a distinct subtype of cutaneous lupus erythematosus that may occasionally present with psoriasiform lesions, creating diagnostic overlap with psoriasis and psoriatic arthritis. This overlap may delay recognition, particularly when inflammatory musculoskeletal symptoms coexist. We report the case of a 23-year-old Arab female who presented with a two-month history of migratory inflammatory polyarthralgia and an eight-year history of recurrent erythematous scaly lesions previously diagnosed as a psoriasiform dermatosis. The lesions predominantly involved sun-exposed areas and were exacerbated by sun exposure and heat. She also had clinically evident Raynaud phenomenon and inflammatory peripheral joint involvement, with tenderness and swelling affecting the wrist, elbows, knees, tarsi, and ankles, in addition to Achilles tendon and plantar fascia tenderness. Psoriatic arthritis was initially considered because of psoriasiform lesions, negative rheumatoid factor, and enthesitis-like symptoms. However, the absence of nail changes, axial symptoms, and radiographic sacroiliitis, together with prominent photosensitivity and Raynaud phenomenon, raised suspicion for SCLE. Antinuclear antibodies (ANA) testing was reportedly negative, but anti-Ro/Sjögren's syndrome antigen A (SSA) antibodies were positive. Skin biopsy from a retroauricular scaly lesion showed epidermal atrophy, follicular plugging, basal vacuolar degeneration, occasional psoriasiform acanthosis, and perivascular/periadnexal lymphocytic infiltration, supporting the diagnosis of SCLE. Treatment with strict photoprotection, hydroxychloroquine, and low-dose prednisolone resulted in marked improvement of cutaneous and joint manifestations over three months. This case emphasizes that psoriasiform morphology and inflammatory joint symptoms should not automatically lead to a diagnosis of psoriasis or psoriatic arthritis. In patients with photosensitive lesions, Raynaud phenomenon, anti-Ro/SSA positivity, and compatible histopathology, SCLE should remain an important diagnostic consideration, even when ANA testing is negative.