Mismatch between fetal sexing and birth phenotype: A case of complete androgen insensitivity syndrome

Abstract

With advancing maternal age, the number of prenatal genetic tests is increasing in many countries. Prenatal genetic tests, such as amniocentesis, chorionic villus sampling and non-invasive prenatal testing, can disclose fetal chromosomal sex, although these tests were originally designed to prenatally diagnose chromosomal aneuploidies, such as trisomy 21, 18 and 13. Complete androgen insensitivity syndrome (CAIS) is an X-linked recessive disorder caused by an androgen receptor dysfunction leading to hormone resistance. The affected individuals are genetic males as shown by 46,XY but present complete female external genitalia and normal breast development at puberty albeit without menstruation. CAIS is commonly diagnosed in adolescence based on primary amenorrhea or in childhood based on inguinal hernia or testis-like masses in the inguinal region. In the present report, we describe a baby in whom CAIS was diagnosed immediately after birth based on a mismatch between the fetal karyotype detected by amniocentesis and the external genitalia phenotype at birth. We speculate that the increase in the number of prenatal genetic tests is contributing to the early detection of 46,XY disorders of sex development, especially those previously called complete sex reversal, which is supposedly diagnosed during childhood or adolescence. Hence, it is necessary to understand the disease-specific hormone profile at each developmental stage for accurate diagnosis.