Picture of the Month—Diagnosis

The scalp lesion was identified as cutis aplasia. Cutis aplasia is a congenital skin defect seen in the neonate. Although somewhat rare, it is important for the examiner to recognize this skin lesion, to understand its pathologic features, and to be aware of the associated anomalies that may coexist in a newborn with cutis aplasia. The majority of these lesions are confined to the scalp and do not pose a great risk to the newborn.

Cutis aplasia is an area with absent skin formation characterized by well-circumscribed, noninflammatory lesions. Most commonly seen as a single lesion at the vertex of the scalp, affected areas can be multiple in number and may be found on the trunk and extremities. The appearance of cutis aplasia varies between an ulcerated, vesicular, or “punched out” appearance. Affected skin depth ranges from the epidermis to the meninges. Superficial ulcerations may undergo epithelialization in utero and present as an area of scarring with alopecia at birth. Most affected areas are small, but documented cases have revealed sizes varying from 0.5 to 100 cm. Larger lesions tend to correspond with greater depth involvement.¹

The cause of cutis aplasia is not well-defined. Most cases are considered idiopathic. Hypotheses have included vascular disruption, pressure necrosis during labor, and amniotic adhesions as possible causes. In addition, several reports have also shown a relation between maternal methimazole use during pregnancy and cutis aplasia.^2-5

The majority of cases of cutis aplasia are sporadic. The incidence is between 0.01% and 0.03%. It is seen in all populations. There have been more than 500 cases reported in the literature.

Cutis aplasia can be seen in association with additional abnormalities or syndromes. Reports have shown both autosomal-dominant and recessive patterns of inheritance.⁶ Frieden⁷ described a classification for cutis aplasia, consisting of groups 1 through 9, based on the numbers of lesions and the presence of additional physical anomalies. Scalp cutis aplasia without additional anomalies composes a group of its own. Other groups include scalp cutis aplasia associated with limb, cardiac, or gastrointestinal anomalies; epidermal nevi; or underlying central nervous system malformations. Cutis aplasia may also be associated with malformation syndromes, including trisomy 13 syndrome, 4p− syndrome, and Adams Oliver syndrome.^7,8

The differential diagnosis for a lesion of this type must include epidermolysis bullosa, herpes, and varicella because these cutaneous diagnoses warrant immediate intervention. Some cases of cutis aplasia have been mistaken as birth trauma. As in this case, when instrumentation was not required during delivery, it is important to explain that neither improper technique nor fetal scalp electrode use contribute to the presence of this anomaly.

When a scalp lesion is noted at birth, it is important to obtain a birth history. Was instrumentation used for the birth, or was a scalp electrode placed? Underlying skull abnormalities may represent central nervous system pathologic abnormalities and will rarely heal without intervention.⁹ A head computed tomography scan is recommended when the cutis aplasia is over the scalp to rule out bony abnormalities.

Most cases of cutis aplasia require local wound care only. Epithelialization usually occurs after birth and creates a hairless scar overlying the site of the defect. No treatment is necessary unless there are signs of an infection. However, reports have described cases of meningitis caused by extravasation of bacteria to the central nervous system in deeper lesions. Surgical repair is sometimes necessary if the lesion is large. Other rare complications include hemorrhage and sagittal sinus thrombi, which may warrant surgical closure.

In conclusion, cutis aplasia is a rare scalp defect. While it can be seen with a number of genetic abnormalities, it is often seen as an isolated defect. Understanding the causes and management is important.

Correspondence: Carolyn Jones, MD, Department of Pediatrics, Loyola University Medical Center, 2160 S First Ave, Bldg 105, Maywood, IL 60153 (cjones4@lumc.edu).

Accepted for Publication: July 1, 2005.