A baby with giant freckles?

The Case

You report to the emergency department to admit a hypoxemic, 2-month-old boy with respiratory syncytial virus (RSV) bronchiolitis. He has been growing well and has no other significant past medical history. As you're listening to his wheezing chest, his mother asks about the "big freckles" on his scalp and forehead that have been present since birth.

CLINICAL FINDINGS

Transient neonatal pustular melanosis occurs in about 5% of black newborns and less than 1% of white newborns.¹ It is a self-limiting, benign condition present at birth.^1,2 It may present in the macular stage or with vesiculopustular lesions lacking surrounding erythema. The lesions rupture easily and leave behind a collarette of scale and a pigmented macule.¹

The pigmented macules are the most commonly visualized lesion. They typically cluster under the chin or on the forehead, nape of the neck, lower back, and shins.¹ The macules are not associated with any symptoms or discomfort and typically fade within a few weeks to a few months. These lesions are unique to transient neonatal pustular melanosis. Contrary to concern decades ago, they do not seem to be the result of an infectious process, and no culture or additional workup is required.

Etiology

The etiology of transient neonatal pustular melanosis remains unclear.¹ Gram stains and bacterial cultures from pustular fluid have not revealed a pathogen. The lesions contain neutrophils, sparse eosinophils, keratinous debris, serous fluid, and fragmented hair shafts.

DIFFERENTIAL DIAGNOSIS

There are many neonatal pustular eruptions. Most are benign, but some are more severe and must be considered.

Erythema toxicum is a benign common condition that differs in that the lesions are surrounded by erythema and that it presents after birth, usually at 24 to 48 hours of life.³

Acne neonatorum occurs in up to 20% of newborns.³ Closed comedones appear on the forehead, nose, and cheeks. Open comedones, papules, and pustules also may develop. Lesions normally clear without treatment within 4 months.

Milia, 1-mm to 2-mm pearly white or yellow papules, are caused by retention of keratin within the dermis.³ They occur in up to 50% of newborns and disappear spontaneously within the first months of life.

In some neonates, pustules are indicative of systemic diseases including neurocutaneous syndromes and oncologic processes.⁴ Incontinentia pigmenti presents with vesicles that may appear pustular, in linear formations along the lines of Blaschko, and that evolve into verrucous lesions over weeks. Pustules in neonatal histiocytosis usually take months to regress and do not leave melanotic lesions.

Bacterial pustulosis is most commonly caused by Staphylococcus aureus but also can be caused by Listeria monocytogenes, Haemophilus influenzae, or group B streptococcus.⁴ Newborns may present with signs of sepsis, and pustular fluid can be cultured to obtain the etiologic agent. Congenital herpes simplex virus or varicella zoster virus lesions classically contain clear fluid, but may appear pustular, and can be identified using the Tzanck smear or polymerase chain reaction.

Congenital melanocytic nevi may present as macular hyperpigmented lesions but are unlikely to be clustered around the scalp line and typically do not regress within the first few months of life.⁵

Our patient

Our 2-month-old infant recovered uneventfully from his RSV infection and had no other dermatologic findings. His mother was relieved that his "forehead freckles" would likely clear soon.

MS SGARLATA is a fourth-year medical student at the University of Illinois College of Medicine, Rockford. DR SKLANSKY is clinical instructor of pediatrics and pediatric hospitalist, University of Illinois-Chicago Medical School, Rockford Memorial Hospital. DR COHEN, the section editor for Dermatology: What's Your Dx? is director, Pediatric Dermatology and Cutaneous Laser Center, and associate professor of pediatrics and dermatology, Johns Hopkins University School of Medicine, Baltimore, Maryland. The authors and section editor have nothing to disclose regarding affiliation with, or financial interest in, any organization that may have an interest in any part of this article. Vignettes are based on real cases that have been modified to allow the authors and editor to focus on key teaching points. Images also may be edited or substituted for teaching purposes.

REFERENCES

1. Ramamurthy RS, Reveri M, Esterly NB, Fretzin DF, Pildes RS. Transient neonatal pustular melanosis. J Pediatr. 1976;88(5):831-835.

2. Liu C, Feng J, Qu R, et al. Epidemiologic study of the predisposing factors in erythema toxicum neonatorum. Dermatology. 2005;210(4):269-272.

3. O'Connor NR, McLaughlin MR, Ham P. Newborn skin: part I. Common rashes. Am Fam Physician. 2008;77(1):47-52.

4. Van Praag MC, Van Rooij RW, Folkers E, Spritzer R, Menke HE, Oranje AP. Diagnosis and treatment of pustular disorders in the neonate. Pediatr Dermatol. 1997;14(2):131-143.

5. Lyon, VB. Congenital melanocytic nevi. Pediatr Clin North Am. 2010;57(5):1155-1176.