Prenatal Diagnosis of a Congenital Postaxial Longitudinal Limb Defect: A Case Report

Introduction. Although congenital longitudinal fibular deficiency is one of the most common long bone deficiencies, there are few published cases of its prenatal diagnosis. Case report. A right longitudinal deficiency of the fibula associated with tibial shortening, foot equinovalgus, and absence of the fourth and fifth foot rays diagnosed at 22 weeks gestation is described. Sequential ultrasonographic surveillance was performed without obstetric complications. The anomaly was confirmed after birth, and conservative orthopaedic management was decided. Conclusion. Though rarely seen, postaxial longitudinal limb defect may be detected by ultrasound. The correct approach can only be decided after birth, when the functional impact of the anomaly can be fully evaluated. 1. Introduction Postaxial longitudinal defect is one of the most common congenital limb reduction defects. This entity includes a large spectrum of abnormalities that may range from severe hypoplasia to complete absence of the fibula and the 5th rays. It is a rare disorder, with an estimated prevalence of 5.7 to 20 cases per 1 million births [1]. Up to now, only few cases of prenatal diagnosis of isolated longitudinal deficiency of the fibula were reported [1–4]. 2. Case Report A 38-year-old healthy primigravida, with no familiar history of limb defects or exposure to teratogenic drugs, was referred to our ultrasound unit at 22 weeks gestation after the absence of the right fibula was diagnosed during the second trimester ultrasound examination. This diagnosis was confirmed in our department. Further assessment of the ipsilateral lower limb detected a discrete femur shortening (35？mm versus 37？mm of left femur, discrepancy of 5.4%), anteromedial bowing and tibial shortening (27.2？mm versus 33.6？mm of left tibia, discrepancy of 19%), see Figure 1, foot equinovalgus, and absence of the fourth and fifth foot rays and digits. All other long bones (humeri, ulnae, and radii) were symmetric and appropriated in length and configuration for gestational age, as were the hands. No other anomalies were detected, namely, craniosynostosis, omphalocele, renal displasia, neural tube defects, thoracoabdominal schisis, or facial dysmorphies. Amniocentesis revealed a normal female karyotype (46, XX). Fetal echocardiography was normal. Follow-up ultrasound examinations were carried out periodically until birth (Figure 2). Tibial discrepancy increased slightly with a difference of 13？mm (23.6%) at 34 weeks gestation. Figure 1: Ultrasound images showing absence of right fibula, bowing of right tibia (a), and