Transient Neonatal Pustular Melanosis (Lentigenes Neonatorum)
Are You Confident of the Diagnosis?
What you should be alert for in the history
Transient neonatal pustular melanosis occurs most commonly in African-American male infants; it can be seen in up to 5% of these babies. It is seen in only 0.6% of Caucasian infants.
Characteristic findings on physical examination
Characteristic lesions, which are present at birth, can be intact or ruptured papulovesicles, 2 to 10mm in size, with a surrounding collarette of scale. Intact lesions are sometimes not seen. This is because of the subcorneal nature of the lesions; they are so friable that they are often wiped off as the infant is bathed for the first time.
Small hyperpigmented macules surrounding the collarettes can be present at birth, or can develop as the pustular lesions resolve, which usually occurs within the first week of life. The hyperpigmented macules usually resolve within 3 weeks to 3 months.
Expected results of diagnostic studies
Histology of a biopsied lesion would show a subcorneal neutrophilic pustule; however, the diagnosis can easily be made without a biopsy by doing a Wright’s stain of pustule contents, which will show numerous neutrophils and only a few eosinophils. A Gram stain will be negative for organisms.
The differential diagnosis would include miliaria crystallina and rubra, herpetic infection (multinucleated giant cells on Tzanck preparation), candidiasis (positive potassium hydroxide examination), erythema toxicum neonatorum (eosinophils on Tzanck preparation), and early-onset acropustosis of infancy (possibly postscabetic). All of these can be differentiated by the appropriate stains used on pustulovesicle contents, be it Wright’s stain, Gram stain, potassium hydroxide, or a Tzanck smear.
Who is at Risk for Developing this Disease?
Any infant can develop this condition; African-American male infants have the highest risk.
What is the Cause of the Disease?
The etiology and pathophysiology of this condition are unknown, although some authors believe the condition may be a variant of erythema toxicum neonatorum.
Systemic Implications and Complications
There are no complications and no systemic implications.
No treatment is necessary, as these lesions are asymptomatic and resolve spontaneously within the first few weeks of life.
Optimal Therapeutic Approach for this Disease
No treatment is needed so there is no therapeutic ladder.
No follow-up is needed once the diagnosis is confirmed because the disease is benign and self-limited.
Unusual Clinical Scenarios to Consider in Patient Management
Be alert for the presence of transient neonatal pustular melanosis in either a very sick febrile neonate or an infant of extremely low birth weight (less than 1kg). In these two settings, the differential diagnosis would have to be expanded to include more unusual infections such as congenital candidiasis or syphilis. In either of these two settings, the work-up would have to be extended beyond simple stains to include samples sent for culture and biopsy.
What is the Evidence?
Ramanurthy, RS, Reveri, M, Esterly, NB. "Transient neonatal pustular melanosis". J Pediatric. vol. 88. 1976. pp. 831-5.(Historically important article. The first case report describing and naming this condition.)
Ferrandiz, C, Coroleu, W, Ribera, M. "Sterile transient neonatal pustulosis is a precocious form of erythema toxicum neonatorum". Dermatology. vol. 185. 1992. pp. 18-22.(This article suggests that transient neonatal pustular melanosis may be a variant of erythema toxicum neonatorum. The evidence against this is that pustular melanosis lesions are full of neutrophils, while erythema toxicum lesions are full of eosinophils.)
Merlob, P, Metzker, A, Reisner, SH. "Transient neonatal pustular melanosis". Am J Dis Child. vol. 136. 1982. pp. 521-2.(An early review of this condition. The article describes the relatively low incidence in the general population, and the increased incidence in African-American infants, especially males.)
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