Partial Androgen Insensitivity Syndrome and Congenital Adrenal Hyperplasia—A Case Report of the Coexistence of Two Rare Diseases in One Patient

<b>Background and Clinical Significance</b>: In a single phenotypically female patient, we describe the rare co-occurrence of partial androgen insensitivity syndrome (PAIS) and congenital adrenal hyperplasia (CAH). Partial androgen insensitivity syndrome (PAIS) is one of disorder of sex development (DSD) with a 46 XY karyotype. Congenital adrenal hyperplasia (CAH) is a genetic defect in adrenal steroidogenesis. <b>Case presentation</b>: We present the case of a 26-year-old female patient who was observed to have abnormally formed external genitourinary organs. She was diagnosed at the neonatal period. Tests performed showed a 46 XY karyotype, an absence of sex chromatin with a weakly positive DNA test for the SRY gene, an absence of uterine primordium with the presence of male gonads in the perineal skin folds, and a urethral outlet at the base of an undeveloped genital process. The daily urinary steroid excretion profile was normal. The patient was diagnosed with partial androgen insensitivity syndrome (PAIS). As a 4-year-old child, she underwent a bilateral gonadectomy due to possible further virilization and also the risk of testicular malignancy. Despite treatment, progressive androgenization was observed, the cause of which turned out to be congenital adrenal hyperplasia (CAH) in the course of P450 oxidoreductase (POR) disorder. <b>Conclusions</b>: In this article, we highlight the exceptional rarity of the co-occurrence of PAIS and CAH, underscoring the need for a multidisciplinary and individualized approach in the absence of clear guidelines regarding surgical timing and gender identity. Careful clinical evaluation and ongoing observation are essential for accurate diagnosis and optimal patient care.