Aplasia cutis congenita of limbs: diagnostic role of prenatal ultrasonography

Introduction

Aplasia cutis congenita (ACC) is a rare congenital malformation, particularly in the trunk, abdomen, or limbs. Prenatal two-dimensional (2D) ultrasound can detect limb structural abnormalities and has become a routine method for prenatal diagnosis. The skin around the trunk of a normal fetus appears hyperechoic on ultrasound. However, three-dimensional (3D) ultrasound can more clearly show the detailed morphology of fetal fingers and toes. Surface pattern imaging is considered the most effective technique for identifying surface anatomy, skin coverage integrity, and the topographic relationships between limb segments (1,2). This study aimed to analyze the prenatal ultrasound features of a fetus with ACC and to determine the diagnostic value of 2D ultrasound combined with 3D ultrasound for ACC.

Case presentation

A 24-year-old pregnant woman was referred to Gansu Provincial Maternity and Child-care Hospital at 23 weeks of gestation with suspected fetal morphological and structural abnormalities of the right buttock and right lower limb. The patient had no medical, surgical, or family medical history. At 23 weeks of gestation, a detailed ultrasonographic examination with a Voluson E10 scanner (GE HealthCare, Chicago, IL, USA), revealed an excess of amniotic fluid but a normal stomach size. Fetal biometry revealed a left femoral length of 40 mm (the 90th to 97th percentile is 42.5 to 44.2) (1), a left tibial length of 34 mm, and a left fibular length of 35 mm (the mean value of the tibia and fibula was 35 mm at 23 weeks) (2). Meanwhile, the length of the right femur was 37 mm, the length of the right tibia was 30 mm, and the length of the right fibula was 11 mm (Figure 1A-1D). The muscle layer in the middle of the right thigh was thinner than that on the left, with a diameter of 15 mm in the right thigh and 22 mm in the left thigh (Figure 1E). Subsequent 3D ultrasonography revealed only the first, second, and third metatarsals and phalanges of the right foot, with the fourth and fifth toe rows missing and a break in continuity of the skin layer in the sacrococcygeal region (Figure 2). After informing the pregnant woman and her family of the possible presence of complications in the fetus, they chose to induce labor at 24 weeks via intrauterine drug injection. Postpartum ultrasonography showed that the right fibula was significantly shorter than the tibia, the left tibia and fibula were of normal length, and there was extensive loss of the skin layer of the right buttock and right lower extremity (Figure 3A,3B). The stillborn fetus was found to have a large skin defect on the right buttock and lower limb (Figure 3C). The parents heeded our genetic counseling advice and underwent testing for whole-exome sequencing. Consequently, one variant of undetermined significance was detected in the fibroblast growth factor receptor 1 (FGFR1) gene, which was partially associated with the participant’s phenotype.

Figure 1 Two-dimensional ultrasound images of the lower limbs of a fetus with ACC. (A-D) Fetal lower limb bone length was measured via two-dimensional ultrasound at 23 gestational weeks. (E) Two-dimensional ultrasonography revealed disrupted sacrococcygeal continuity (red arrows), loss of skin hyperechogenicity in the right lower extremity (red arrows), a shorter right femur, and a smaller right thigh diameter as compared to the left. ACC, aplasia cutis congenita; FIB, fibula; FL, femur length; L, left; R, right; TIB, tibia.

Figure 2 3D ultrasound findings. 3D ultrasound showed a varus right foot with only the first, second, and third toes visible (A,C; white arrows), with the skin of the right buttock and right lower limb being exfoliated (B; white arrow). 3D, three-dimensional.

Figure 3 Postnatal ultrasound images and specimens of a fetus with ACC. (A) An ultrasound image showed hyperechogenicity of the skin layer in the left thigh (white arrows). (B) An ultrasound image indicated disappearance of the skin layer in the right thigh (white arrows). The right fibula was significantly shorter than the tibia (B; red arrows). (C) Pathomorphological specimen of the same aborted fetus. ACC, aplasia cutis congenita; L, left; R, right.

All procedures in this study were performed in accordance with the ethical standards of the relevant institutional and/or national research committee(s) and with the Declaration of Helsinki and its subsequent amendments. Written informed consent was obtained from the patient for publication of this article and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Discussion

ACC is a condition characterized by focal or extensive and complete or partial absence or scarcity of skin at birth. Cases of multiple skin lesions are extremely rare. ACC was first reported in 1767 by Cordon and involved the extremities. In 1826, Campbell first described congenital cutaneous ACC of the scalp (3,4). The incidence of ACC has been reported to be 3 of 10,000 births (5), but the etiology of ACC is not well defined. Factors discussed include hereditary or episodic factors, intrauterine necrosis, intrauterine infection, intrauterine pressure, cerebrovascular pathology, amniotic adhesions, and teratogens (6). We report a case of a fetus with congenital cutis hypoplasia on the right buttock and lower extremity with syndactyly of the right fourth and fifth toes. Transmission electron microscopy of fetal skin biopsies and immunofluorescence studies are currently the only methods for achieving definitive prenatal diagnosis; however, this approach is invasive. In our experience, ACC of the trunk can be detected in prenatal ultrasound examination. In 1990, Meizner and Carmi (6) described a new ultrasound “snowflake” sign, which may be useful in establishing an early diagnosis of intrauterine skin-exfoliation syndrome; however, in our case, echo-clear amniotic fluid was present. In a healthy fetus, the skin surrounding the trunk generates strong echoes. When ACC occurs, these strong echoes will be absent. On 3D ultrasound, there is localized disruption of skin continuity, and 3D ultrasonography is the method of choice for optimal morphological reconstruction of fetal extremities and can visualize the detailed morphology of fingers and toes. Surface-mode imaging is the preferred technique for recognizing surface anatomy, integrity of skin cover, and topographic relationships between the segments of each limb. Visualization of the malformations and deformations of fetal extremities is of particular importance within the group of systemic skeletal dysplasias (7,8). For ultrasound-based prenatal testing for ACC, first, fetal karyotyping and genetic testing are recommended, and 3D ultrasound can provide a clearer image of the integrity of skin coverage and the spatial relationships between limbs in the case of generalized bone dysplasia.

Conclusions

In conclusion, our case is among the rarest instances of ACC due to the combined limb deformity. Detection may be difficult but is possible with careful examination. Early recognition can assist in the counseling of parents and provide information critical to the planning of perinatal treatment.

Acknowledgments

None.

Footnote

Funding: This work was supported by the Science and Technology Program of Gansu Province (No. 23JRRA1383).

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://qims.amegroups.com/article/view/10.21037/qims-2025-431/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All procedures in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Declaration of Helsinki and its subsequent amendments. Written informed consent was obtained from the patient for publication of this article and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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