Aplasia cutis congenita (ACC) is a rare malformation characterized by the localized absence of skin, which may extend through the underlying tissues to the musculature and bone. Aplasia cutis congenita associated with fetus papyraceus is classified as type V ACC. We present a case of type V ACC with extensive truncal lesions.
Ultrasonic examination has become a conventional method in prenatal diagnosis. Many congenital malformations can be detected by ultrasound (US). Abnormalities in the structure of the abdominal wall can be detected in prenatal US examination. In the normal fetus, the abdominal skin surrounding the trunk generates strong echoes on US. In the present case, strong echoes were unobtainable for part of the abdomen.
A 28-year-old woman (gravida 3, para 1, abortus 1) presented for US examination at 13 and 32 weeks of gestation. At 13 weeks of gestation, US showed a twin pregnancy with one death. At 32 weeks, US examination displayed only one fetus. The surviving fetus was smaller than expected for the post-menstrual period. Measurements calculated in US indicated a fetus at 28 weeks of gestation. When we examined the trunk, sagittal and cross-sectional US scans demonstrated that the abdominal skin was absent. In a normal fetus, the skin surrounding the trunk generates strong echoes. In the present case, strong echoes were absent for some of the abdominal circumference. The liver appeared to be exposed. No strong echo was generated between the liver and amniotic fluid. We designated this US characteristic as indicating “absence of skin” (Fig. 1). The positions and shapes of intra-abdominal organs were normal. No other structural abnormality was found. We excluded gastroschisis, omphalocele and Prune belly syndrome. Ultrasonic diagnosis indicated that: (i) fetal intrauterine growth was retarded, and (ii) fetal abdominal skin was absent.
The patient was delivered vaginally at term with a macroscopically normal placenta. Apgar scores were 10 and 10 at one minute and five minutes, respectively. The infant was male and weighed 1850 g. A 95 × 45 × 10-mm fetus papyraceus was also delivered.
On examination of the newborn, extensive defects were seen on the trunk. The infant presented with symmetrical abdominal wall lesions. Vessels were prominent, and the abdomen was covered with a translucent protective membrane (Figures 2 and 3). The infant was diagnosed by a dermatologist as having ACC.
Overall, 15% of cases of ACC involve locations other than the scalp. These non-scalp locations are often bilaterally symmetrical. A total of 10% of all non-scalp variants of ACC are associated with fetus papyraceus. This cutaneous type is usually linked with the death of a second fetus in utero, which results in the delivery of a fetus papyraceus. The vascular theory is upheld as a likely etiology for type V ACC.
The timing of the disappearance of one or more fetuses is extremely important in predicting the outcome of the remaining fetus. If vanishing twin syndrome occurs during the second half of pregnancy, the remaining fetus may develop cerebral palsy or extensive aplasia cutis. At 13 weeks of gestation, we were able to identify the shape of the dead fetus. At 32 weeks of gestation, only one fetus was detected. Thus vanishing twin syndrome occurred in the second trimester.
The literature includes reports of only two cases[8, 9] in which membranous ACC of the scalp was detected in utero. Cambiaghi et al. reported that the “hair collar” sign may be a marker for ectopic neural tissue. The “hair collar” sign, which was found at birth, was surrounded by long, dark hair, had well-defined boundaries, and followed the regular shape of the scalp defect. In the US, the disorder appears as a protruding, round lesion on the scalp. To our knowledge, no cases of ACC with truncal lesions have been reported in utero.
In our experience, ACC of the trunk can be detected in prenatal US examination. In the normal fetus, the abdominal skin surrounding the trunk generates strong echoes. When ACC occurs, these strong echoes will be absent. In the present case, the positions and shapes of intra-abdominal organs were normal. No organ was found in the amniotic fluid. The intra-abdominal organs seemed to be exposed. Indications of absence of skin may be found in US images. Compared with membranous ACC of the scalp, the area of the truncal lesion was larger and irregular. The whole lesion could not be displayed in a single US image. Whereas membranous ACC on the scalp appears in US as a protruding, round lesion, ACC lesions on the trunk do not generate strong echoes. The US sign for absence of skin over intra-abdominal organs may represent a typical finding in this condition. This sign should be regarded as a distinct marker and used to differentiate such ACC lesions from protruding lesions. According to the medical history of the fetus, a prenatal diagnosis of type V ACC should be strongly considered when such a lesion is visualized on prenatal US. The “absence of skin” sign indicating the absence of abdominal skin may not be obvious. Detection may be difficult but is possible with careful examination. Early recognition will assist in the counseling of parents and provide information important for planning perinatal treatment.