A healthy full-term newborn presented with a prominent sacral dimple within an oval patch. Ultrasound showed no evidence of spinal anomalies, and the child was discharged home. Three days later, the patch became elevated, red, and moist appearing, and she was brought to the emergency department (ED) for further evaluation of the “growing blister.”
Examination and testing
The infant continued to feed and stool appropriately and was able to move her upper and lower extremities equally with no signs of weakness, although she had not voided for 23 hours. Concerned about the enlarging lesion, the patient’s mother brought her to the pediatric ED.
In the ED, the neonate’s exam was significant for a sacral dimple with a small opening and a 2.5-cm by 2.5-cm erythematous and moist-appearing "protruding sac" on her lower back that oozed serous fluid, thought to be cerebrospinal fluid (CSF). The Neurosurgery service was consulted, who recommended vancomycin and cefepime out of concern for myelomeningocele with external communication. An ultrafast magnetic resonance imaging (MRI) of the brain and lumbar spine was obtained, which was read as most consistent with a noncommunicating cyst in the subcutaneous soft tissues, although communication with the spinal canal could not be excluded. A urinalysis was obtained given the initial concern for obstruction but showed no evidence of infection. The neonate was admitted to the neonatal intensive care unit (NICU) for monitoring and further diagnosis (Table 11-8).
The Dermatology service was then consulted, who described the lesion as a “well-circumscribed flaccid erythematous-violaceous blister” with a thick overlying membrane (Figure). The Dermatology team diagnosed the lesion as membranous aplasia cutis congenital (ACC).
Aplasia cutis congenita has been estimated to have an incidence of 3 in 10,000 births.4 More than 500 cases have been described in the medical literature,9 but it is believed to be underreported because of its often benign nature. No predilection for race or sex has been reported.4