Prenatal diagnosis of apert syndrome at 23 weeks: a case report with isolated syndactyly and sacrococcygeal appendage preceding cranial malformation.

BACKGROUND: Apert syndrome is a rare congenital malformation caused by a mutation in the fibroblast growth factor receptor 2 (FGFR2) gene. Characteristic imaging findings include bilateral premature closure of the coronal suture, midfacial hypoplasia, and symmetrical syndactyly of the fingers and toes. These features may be accompanied by lateral ventricle dilation, absence of the corpus callosum, cervical vertebral fusion, and other anomalies. However, in the second trimester, syndactyly and extracranial anomalies may be the only detectable signs, which complicate early diagnosis. The purpose of this study is to improve the early diagnosis rate of Apert syndrome.

CASE DESCRIPTION: We report an atypical case of Apert syndrome carrying the FGFR2 S252W mutation, which typically associated with severe cranial deformities and cleft palate, but prenatal ultrasound at 23 weeks revealed symmetrical syndactyly of both hands and feet and a sacrococcygeal soft tissue mass resembling a "tail" without cranial abnormalities. Although prior studies have linked this mutation to advanced paternal age, the father in this case was 25 years old, which does not align with this association.

CONCLUSIONS: This case demonstrated that Apert syndrome may present prenatally features other than cranial abnormalities. A practical screening strategy should therefore combine detailed second-trimester ultrasound evaluation of extremities and cardiac structures with prenatal genetic testing, even in the absence of cranial abnormalities.