Swyer syndrome and complete androgen insensitivity syndrome are disorders of sex development in which patients present a female phenotype and 46,XY karyotype.

The authors present a case report of an 18-year-old patient with primary amenorrhea and delayed puberty. The karyotype was 46,XY. No mutations of sex-determining region Y gene and androgen receptor genes were identified, and imaging methods failed to show müllerian structures. A diagnosis of complete androgen insensitivity syndrome was presumed, but after hormonal replacement therapy was started a “hidden” uterus developed, leading to the definite diagnosis of Swyer syndrome.

The diagnosis of Swyer syndrome can be challenging, because visualization of müllerian structures is sometimes difficult and analysis of genetic mutations is not helpful in the majority of cases.