Ultraviolet light exposure is not a requirement for the development of cutaneous neonatal lupus.

Cutaneous neonatal lupus erythematosus (NLE) is a rare disorder, linked to the presence of transplacentally acquired maternal autoantibodies (anti-ENA). NLE skin lesions frequently appear in the second or third month of life, and ultraviolet exposure is thought to be an initiating factor since it can externalize intranuclear autoantigens at the cell surface. We report a baby who was born already with an extensive NLE rash, suggesting that sun exposure is not a requirement for the development of NLE skin lesions. A 31-year-old woman affected with mixed connective tissue disease gave birth to a female after 38 weeks of gestation. Pregnancy was uneventful and no perinatal complications were seen. The mother was positive for anti-RNP, but negative for anti-SSA/Ro and SSB/La autoantibodies. Already at birth, an extensive scarring rash with a few erythematosus lesions was present on the baby's face and scalp; this progressed over the following months, and subsequently stabilized. Anti-RNP were present in the baby's serum. Due to the unusual features of the disease expression, a skin biopsy was performed at age 5 months; results were consistent with the diagnosis of NLE, showing mononuclear cell infiltration and immunoglobulin deposition. No other features of NLE were detected. This observation is unusual for: (1) the presence of an NLE rash in the absence of anti-SSA/Ro; (2) the scarring and atrophic characteristics of the lesions; and (3) the development already in utero. This latter finding argues against sun exposure being necessary for lesion induction.