Background Incontinentia pigmenti (IP) is a rare, X-linked genodermatosis caused by mutations leading to loss of Nuclear factor kappa B (NFκB) activation. It is generally considered to be lethal in utero in male fetuses, suggesting that normal gene expression is critical for survival.

Objective The purpose of this study was to characterise inflammatory mediators in skin lesions of newborns with IP, and to illustrate the skewed X chromosome inactivation pattern of the disease.

Methods 1–2 punch biopsies were obtained from each of four newborn females with IP, and analysed for expression of the antimicrobial peptides LL37, Psoriasin, and High mobility group box 1 (HMGB1), by using immunohistochemistry, double immunofluresensce, and immuno electron microscopy. Skin biopsies from four newborns and four adults were used as controls. In addition, an X-inactivation assay based on methylation-specific PCR was performed in blood and lesional/non-lesional skin tissues from one infant.

Results A higher expression of LL37, Psoriasin, and HMGB1 was found in the lesions of IP compared to normal skin. The amount of LL37 was 3.5 times higher in eosinophils recruited into the IP lesion than in eosinophils isolated from cord blood of healthy newborns. A skewed X-inactivation pattern was found in blood, but not in lesional or nonlesional skin.

Conclusions Our results demonstrate that LL37, Psoriasin and HMGB1 are upregulated in the skin lesions of newborn females with IP. These data will be of importance for further studies regarding the inflammatory stages of IP in the newborn infant.