Flea-bitten baby

February 19, 2015

Clinical Vignette

You are called to the emergency room to calm a panicked mother with a healthy 9-day old baby who awoke this morning with disseminated pustules (figures 1-3). What’s the diagnosis?

Diagnosis and Clinical Presentation

On examination you note 1-2 mm pustules on a red urticarial base giving the flea-bitten appearance typical of erythema toxicum neonatorum (ETN). The eruption is most dense on the trunk but lesions are also scattered on the face and extremities. She is afebrile and feeds well in the emergency room The infant was delivered vaginally at term to a healthy mother who had an uncomplicated pregnancy. ETN occurs in 30-70% of newborns and usually presents between the first and fourth days of life. The vesiculopustular rash consists of white-yellow lesions with surrounding erythema and typically lasts 2-3 days. The asymptomatic lesions predominate on the trunk, but may involve the extremities, and usually spare the palms and soles.1 Case reports have documented ETN in newborns up to 2 weeks of age.2-3

Epidemiology and pathogenesis

Although the underlying cause remains uncertain, some investigators have suggested that the presence of eosinophils may provide a clue.4 Proposed etiologies include a graft-versus-host reaction induced by maternal cells, skin reaction to perinatal mechanical and thermal stimulation, and obstruction of sebaceous glands.3 Allergic and infectious etiologies have been suggested, but no specific allergen or infection has been linked to ETN. A recent epidemiologic study showed that term gestation, vaginal delivery, and formula feeding were associated with higher rates of ETN.1 There are no known short or long term complications associated with ETN.

Differential Diagnosis

Although ETN is common and often viewed as a normal variant in the nursery, a wide differential for vesiculopustular rashes should be considered, especially with an atypical presentation such as in our patient. Benign pustular eruptions: Transient neonatal pustular melanosis differs from ETN in that it presents with pustules that are more impressive than erythema, and with evidence of lesions present at birth. The lesions can appear on any surface, including the palms and soles, and regress by 2 weeks of age, often leaving hyperpigmented skin. Eosinophilic pustular folliculitis may present in the newborn period with yellow pustules on erythematous bases localized mostly to the scalp. Lesions usually resolve in several days, but may recur in crops multiple times during infancy. Neonatal acne, also known as benign cephalic pustulosis, is hypothesized to result from maternal hormonal stimulation, and occurs in about 20% of newborns. The pustular lesions are localized to the face and typically resolve by 3 months of age.5 Infectious diseases: Suspicion of infectious agents warrants culture of the lesion, and likely further infectious workup with possible IV medications. Neonatal Herpes Simplex Virus (HSV) infection usually manifests with grouped vesicles or crusted papules, but more widespread lesions may occur. HSV onset peaks around 10-12 days of life and is likely to also present with fever, lethargy and poor feeding.6 Neonatal varicella zoster virus (VZV) infection may also present with fever and crops of vesicular lesions that may coalesce and become hemorrhagic. Severe VZV infection may lead to other organ involvement. Bollous impetigo can present with one ore more pustular lesions with surrounding erythema, and is likely to be caused by Staphylococcus aureus. Congenital candidiasis may present with papulovesicles and erythema soon after birth, often with palm and sole involvement.5 Other neonatal eruptions Milia often presents on the face with 1-2mm firm papules. It is caused by retention of keratin in the dermis, with eventual resorption and subsequent resolution usually in the first month of life. Miliaria is caused by sebaceous gland obstruction at different levels. Miliaria crystallina results from distal obstruction of eccrine ducts, and presents with 1-2mm vesicles. There is no erythema and the lesions disappear as desquamation occurs over hours to days. Miliaria rubra results from a more proximal obstruction, often associated with heat, and thus occurs in covered areas. It presents with erythematous papules and vesicles.7 Incontinentia pigmenti is an X-linked dominant condition occurring mostly in females. It presents in the first few weeks of life with inflammatory linear pustules along the lines of Blaschko.

Our Patient

Our 9 day old male was well appearing, afebrile, had no risk factors for infectious diseases, and had lesions with the appearance and distribution of ETN. Therefore no further workup was pursued and he was sent home from the ER with the reassuring diagnosis of ETN.

Conclusion

Erythema toxicum neonatorum is a common benign self-limited pustular eruption of the newborn that should be distinguished from potentially serious bacterial, viral, and fungal infections in early infancy.

References

  1. 1. Liu C, Feng J, Qu R, Zhou H, Ma H, Niu X, Dang Q, Zhang X, Tian Z. Epidemiologic study of the predisposing factors in erythema toxicum neonatorum. Dermatology. 2005;210(4):269-72 2. Akoglu G, Ersoy Evans S, Akca T, Sahin S. An unusual presentation of erythema toxicum neonatorum: delayed onset in a preterm infant. Pediatr Dermatol. 2006 May-Jun;23(3):301-2. 3. Chang MW, Jiang SB, Orlow SJ. typical erythema toxicum neonatorum of delayed onset in a term infant. Pediatr Dermatol. 1999 Mar-Apr;16(2):137-41. 4. Boralevi F. Erythema toxicum neonatorum: still a problem in 2005? Dermatology. 2005;210(4):257-8. 5. Wagner A. Distinguishing vesicular and pustular disorders in the neonate. Curr Opin Pediatr. 1997 Aug;9(4):396-405. 6. Kimberlin DW, Whitley RJ. Neonatal herpes: what have we learned. Semin Pediatr Infect Dis. 2005 Jan;16(1):7-16. 7. O'Connor NR, McLaughlin MR, Ham P. Newborn skin: Part I. Common rashes. Am Fam Physician. 2008 Jan 1;77(1):47-52.

Diagnosis and Clinical Presentation Tags

Pattern

Morphology

Pigmentation

Body Site

Anatomic Depth