Development of photosensitivity and an SLE-like syndrome in a patient with psoriasis

An unusual case of photosensitive psoriasis and systemic lupus erythematosus-related syndrome was characterized by erythroderma, chronic urticaria, angioneurotic edema, intermittent low-grade fever, and polyarthralgias. Investigation revealed no measurable total hemolytic complement and markedly diminished levels of C4, C2, and C3. Microscopic examination of three skin biopsy sections of sun-exposed skin showed psoriasis. Skin biopsy sections of sun-exposed psoriatic plaques and of non-sun-exposed, uninvolved skin (which were stained with fluorescein-tagged anti-IgG, anti-IgM, anti-IgA, and anti-C3) showed granular deposits of IgM and C3 at the dermal-epidermal junction in the sun-exposed plaques, and IgM alone in a granular pattern at the dermal-epidermal junction in uninvolved skin. Antibodies to single-stranded but not double-stranded DNA were detected in the patient's serum. In addition, serum immune complex-like material was detected by sucrose density-gradient ultracentrifugation, standard anticomplementary assays, and radioimmunoassays using both C1q and monoclonal rheumatoid factor.