Urticaria Neonatorum: Accumulation of Tryptase-Expressing Mast Cells in the Skin Lesions of Newborns with Erythema Toxicum

    December 2007 in “ Pediatric allergy and immunology ”
    Arne Nelson, Ann‐Kristin Ulfgren, Josefine Edner, Berit Ståbi, Hjalmar Brismar, Kjell Hultenby, Giovanna Marchini
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    Studysummary In this study, researchers found that mast cells in Erythema Toxicum lesions in newborns are actively involved in the immune response around hair follicles, but do not express the antimicrobial peptide LL-37. Our plain-language summary of this paper — not a Tressless recommendation.
    The study investigated the role of mast cells (MCs) in Erythema Toxicum, a common rash in newborns, by examining the presence of tryptase-expressing MCs and the cathelicidin peptide antibiotic LL-37 in the skin lesions. The study included skin samples from 7 infants with the rash, 6 without, and 3 adults. It was found that numerous tryptase-expressing MCs were recruited around the hair follicles in the lesions, and these MCs showed signs of degranulation, indicating activation. However, neither the skin MCs from the newborns nor from the adults expressed LL-37. The results suggest that MCs are actively involved in the innate immune response of Erythema Toxicum, particularly around the hair follicle, but their activity does not involve the LL-37 peptide. This points to a significant role for MCs in the body's initial immune defense during the critical period of perinatal colonization.
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