Suspicious blister on a newborn’s scalp

The vertex of the neonate's scalp displays a solitary, round, 1 cm by 1 cm, slightly erythematous bullous lesion that does not feel fluctuant or fluid filled. Hair surrounding the lesion is similar in color, texture, and length to the reaminder of hair on the scalp.

THE CASE

You are called to the nursery to evaluate a vigorous, healthy-appearing, small-for-gestational-age, full-term, 2-day-old boy with a blister on the vertex of his scalp that was noted in the delivery room. You are worried about infection, so you order a sepsis workup and start parenteral antibiotics and acyclovir, pending culture results. FOR MORE ON THIS CASE, TURN TO NEXT PAGE.

DERMCASE diagnosis}  BULLOUS APLASIA CUTIS CONGENITA

Discussion

Although aplasia cutis congenita (ACC) most commonly presents with a solitary lesion at the vertex of the scalp (Figure), fewer than 20 cases of “bullous” aplasia cutis congenita have been reported, including this case.^1,2 Aplasia cutis congenita refers to a heterogeneous group of skin lesions characterized by congenital focal absence of the skin and the morphologic changes that develop when the defect heals. The typical midline posterior scalp lesion presents with a 0.5- to 5.0-cm sharply demarcated, flattened, depressed, or hypertrophic scar or superficially eroded or deeply ulcerated plaque. Rarely, the defect is covered by a membranous epithelium giving the appearance of a bulla (hence, bullous ACC).

Notably, around 25% of ACC cases have an underlying bony or dural defect. On review of the literature, however, roughly 65% of known cases presenting with bullae have an associated bone defect.² The "hair collar" sign is another well-known marker for cranial defects associated with ACC, such as ectopic neural tissue, encephaloceles, and meningoceles.³ These patients present with a round plaque or nodule surrounded by hair that is longer, darker, and coarser than the other hair on the scalp, similar to the tuft of hair that is seen over lumbosacral myelomeningoceles. Thus, ACC can have a widely variable presentation, along with the potential for multiple other anomalies.⁴

Aplasia cutis congenita presenting with a “bulla” or a “hair collar” sign may need further evaluation to exclude the presence of bony defects. Initial evaluation can be done with cranial ultrasound given its low cost, lack of radiation, no need for sedation, and widespread availability. Should additional evaluation be warranted, magnetic resonance imaging of the brain and spine would be prudent. There may be a reporting bias in the literature because, in the experience of the section editor, most newborns with a hair collar sign have no evidence of communication with the underlying central nervous system. Moreover, the presence of meningeal tissue, which the section editor refers to as meningeal “rests,” if one is brave enough to biopsy the central plaque, is the usual histopathologic finding and does not require further evaluation in otherwise normal infants and children.

The differential diagnosis includes herpes simplex virus (HSV), which often presents with clusters of uniform vesicles, and birth trauma from use of scalp electrodes or forceps, which is easily excluded by history.⁵

The etiology of ACC is unknown and likely includes genetic factors, trauma, and vascular insufficiency that may be associated with rapid head growth in utero. One proposed mechanism is that this may arise from an abnormality of separation of the epithelial and neural ectoderm at eural tube closure.

Management

Beyond appropriate workup for cranial and neural defects, many lesions have already healed in utero and do not require further treatment. Erosions less than 3 cm in diameter can be treated with conservative wound care and use of topical therapy such as bacitracin or petrolatum.⁵ Larger lesions may require surgical investigation and closure.¹

Our patient

The patient’s HSV studies, including surface cultures, cerebrospinal fluid polymerase chain reaction (PCR), and serum PCR were all negative. The primary diagnosis of ACC was made and cranial ultrasound showed normal sonographic appearance of the brain; absence of bony defect; and extension of the membranous lesion in the subcutaneous tissue. The infant displayed no focal neurologic deficits and had appropriate tone and neonatal reflexes. The family opted for conservative treatment and planned to use topical antibiotics only if the lesion ulcerated.

REFERENCES

1. Garcia-Romero MT, Narvóez-Rosales V, Hojyo-Tomoka MT. Bullous aplasia cutis congenita: case report and review of the literature. Indian J Dermatol. 2011;56(3):337-338.

2. Colon-Fontanez F, Fallon Friedlander S, Newbury R, Eichenfield LF. Bullous aplasia cutis congenita. J Am Acad Dermatol. 2003;48(5 suppl):S95-S98.

3. Drolet BA, Clowry L Jr, McTigue MK, Esterly NB. The hair collar sign: marker for cranial dysraphism. Pediatrics. 1995;96(2 pt 1):309-313.

4. Frieden IJ. Aplasia cutis congenita: a clinical review and proposal for classification. J Am Acad Dermatol. 1986;14(4):646-660.

5. Browning JC. Aplasia cutis congenita: approach to evaluation and management. Dermatol Ther. 2013;26(6):439-444. 

Dr Gilbert is a pediatrics resident, All Children’s Hospital, Johns Hopkins Medicine, St. Petersburg, Florida. Dr Pena is a neonatal-perinatal fellow, University of South Florida, Tampa. Dr. Shakeel is a neonatologist, All Children's Hospital, Johns Hopkins Medicine, St. Petersburg. Dr Cohen, section editor for Dermcase, is professor of pediatrics and dermatology, Johns Hopkins University School of Medicine, Baltimore, Maryland. The authors and section editor have nothing to disclose in regard to affiliations with or financial interests in any organizations that may have an interest in any part of this article. Vignettes are based on real cases that have been modified to focus on key teaching points. Images also may be edited or substituted for teaching purposes.