| Synonym: | Transient neonatal pustulosis[1] and lentigines neonatorum[2] |
| Specialty: | dermatology, pediatrics |
Transient neonatal pustular melanosis (TNPM), also known as pustular melanosis, is a type of neonatal pustular eruption that is a transient rash common in newborns. It is vesiculopustular rash made up of 1–3 mm fluid-filled lesions that rupture, leaving behind a collarette of scale and a brown macule.[3] The lesions are fragile and with no surrounding erythema.[3] This rash occurs only in the newborn stage, usually appearing a few days after birth,[4] but pigmented macules are sometimes already present at birth.[3] The rash usually fades over three to four weeks but may linger for up to three months after birth.[3] It can occur anywhere on the body, including the palms and soles.[4]
The cause of TNPM is unknown. It has been suggested that TNPM is merely a variant of erythema toxicum neonatorum[3] or a "precocious" form of erythema toxicum neonatorum.[5] No treatment is needed except for parental reassurance.
Transient neonatal pustular melanosis was initially described in 1961 as lentigines neonatorum[6] and as such was not fully distinguished from other similar rashes.
Transient neonatal pustular melanosis was clearly identified in 1976 by Ramamurthy et al.[6] [7]
The cause of TNPM is unknown.[3]
It has been suggested that TNPM is merely a precocious form of erythema toxicum neonatorum based on the similar histopathology.[5]
Transient neonatal pustular melanosis is diagnosed clinically, based on appearance alone, with no need for special testing. Proper identification is important to distinguish it from other serious, infectious neonatal diseases[3] and to help avoid unnecessary diagnostic testing and treatments.
A smear of the pustular contents will show polymorphic neutrophils and occasional eosinophils on Wright's stain.[3]
On histopathology, the pigmented macules will show basal and supra-basal increase in pigmentation without any pigmentary incontinence.[3] Bacterial culture will be negative.[5]
Increased frequency of placental squamous metaplasia has been reported in the mothers of some of these infants.[8]
No treatment is needed except for parental reassurance. The rash spontaneously resolves, usually in three to four weeks, but the pigmented macules may linger for up to three months after birth.[3]
The incidence of TNPM is 0.6% in white infants and 4.4% in African-American infants in the United States.[9] This rash also generally has a higher incidence in non-African-American infants with skin of color.[9]
There is significant regional variation and the incidence can vary widely in other nations. For example, in Brazil, transient neonatal pustular melanosis occurs in 9.6% of all newborns.[10]
TNPM occurs equally in both sexes.[9]
Genetic influence is unlikely as it has been reported in only one of pairs of identical twins.[10]