Cutaneous neonatal lupus erythematosus: discordant expression in identicaltwins.

Background, Neonatal lupus erythematosus is a rare syndrome characterized e ssentially by cutaneous lesions and/or congenital heart block occurring in infants at birth, or shortly after. It is related to transplacental crossin g of maternal auto antibodies (usually anti Ro/SS-A, La/SS-B or rarely anti -U,RNP) from the mother to the infant. Mothers of affected children have si gns of systemic lupus erythematosus or other collagenosis or are asymptomat ic. Case report. We report a case of neonatal lupus erythematosus in one identi cal twin, revealed at the age of 3 months by erythematous and annular cutan eous lesions of the face and limbs. These lesions were preceded at birth by an asymmetrical livedo pattern of the lower limbs. Her twin sister was una ffected but both infants had a high rate of anti-Ro/SSA antibodies. The dia gnosis of neonatal lupus erythematosus permitted to reveal a biological lup us syndrome in their asymptomatic mother. Cutaneous lesions cleared almost completely within 1 year whereas antiRo/SSA antibodies disappeared. Conclusion. Cases of neonatal lupus erythematosus in twins are rare and mos tly described in heterozygotic twins. Clinical discordance is usual and cou ld partly be explained by genetic factors. In monozygotic twins, like in ou r case, chromosome X inactivation could be an explanation of the difference s observed.