Search

At birth, commensal microbes penetrate into the skin of the human newborn, eliciting an acute rash, erythema toxicumn neonatorum. Histologically, the rash is characterized by an upregulation of proinflammatory activity and a local recruitment of immunocytes, including macrophages. High mobility group box chromosomal protein 1, a nuclear and cytosolic protein, is also a pro-inflammatory cytokine released by macrophages in response to microbial stimulation. Here, we reasoned that macrophages but also keratinocytes might upregulate this protein in response to the first colonization and that high mobility group box chromosomal protein 1 might play a role as a proinflammatory mediator in the development and progression of erythema toxicum. Punch biopsy specimens from 1-day-old healthy infants, seven with and four without erythema toxicum were analyzed with indirect immunohistochemistry and two different antihigh mobility group box chromosomal protein 1 antibodies, immunofluorescence, nuclear counterstaining, confocal and immunoelectron imaging. We found relocation of nuclear high mobility group box chromosomal protein 1 into the cytoplasm in keratinocytes and macrophages in erythema toxicum. Cytoplasmatic high mobility group box chromosomal protein 1 was also found in melanocytes and did neither co-locate with lysosomal-associated membrane proteins nor with melanosomes. We speculate that terrestrial adaptation triggers the induction of the endogenous "danger signal" high mobility group box chromosomal protein 1 in the skin of the newborn infant, perhaps in response to the first commensal colonization and that this signal may contribute to alert the immune system and promote a protective immune response.

Pseudomonas aeruginosa septicemia is rare in healthy infants and children. Also not common, dermatologic manifestations such as ecthyma gangrenosum and indurated erythematous nodular lesions may be the first signs of pseudomonas infection, or may appear later in the course of the disease. Peripheral facial paralysis and mastoiditis are also rare and serious complications of acute otitis media caused by P. aeruginosa. We report a previously healthy 6-month-old boy who had an uncommon presentation and rare complications during the course of P. aeruginosa sepsis.