Neonatal Pustular Melanosis Workup

Updated: Dec 18, 2019
  • Author: Robert A Silverman, MD; Chief Editor: Dirk M Elston, MD  more...
  • Print

Laboratory Studies

If the appearance is typical of transient neonatal pustular melanosis, no further workup is indicated. If appearance is not typical, potassium hydroxide preparation, Gram stain, and Wright-Giemsa stain can support other diagnoses in the differential. In atypical cases, pustules can be cultured for bacteria and clustering of pustules should prompt polymerase chain reaction to identify possible herpes simplex.

Wright-Giemsa stain of pustule contents demonstrates a predominance of neutrophils. Few, if any eosinophils are present. The brown macules are not true freckles or lentigines. Skin biopsy shows pigment incontinence characteristic of postinflammatory hyperpigmentation. The diagnosis of Langherhans cell histiocytosis can only be made by skin biopsy.