A Case of Bilateral Testicular Tumors Subsequently Diagnosed as Congenital Adrenal Hyperplasia Due to 21-Hydroxylase Deficiency

21-hydroxylase deficiency (21-OHD) caused congenital adrenal hyperplasia (CAH) is a group of autosomal recessive genetic disorders resulting from mutations in genes involved with cortisol (CO) synthesis in the adrenal glands. Testicular adrenal rest tumors (TARTs) are rarely the presenting symptoms of CAH. Here, we describe a case of simple virilizing CAH with TARTs, in a 15-year-old boy. The patient showed physical signs of precocious puberty. The levels of blood adrenocorticotropic hormone (ACTH), urinary 17-ketone steroids (17-KS), dehydroepiandrosterone sulfate (DHEA-S), and serum progesterone (PRGE) were elevated, whereas those of follicle-stimulating hormone (FSH), luteinizing hormone (LH), and CO were reduced. Computed tomography (CT) of the adrenal glands and magnetic resonance imaging (MRI) of the testes showed a soft tissue density (more pronounced on the right side) and an irregularly swollen mass (more pronounced on the left side), respectively. Pathological examination of a specimen of the mass indicated polygonal/circular eosinophilic cytoplasm, cord-like arrangement of interstitial cells, and lipid pigment in the cytoplasm. Immunohistochemistry results precluded a diagnosis of Leydig cell tumors. DNA sequencing revealed a hackneyed homozygous mutation, I2g, on intron 2 of the CYP21A2 gene. The patient’s symptoms improved after a three-month of dexamethasone therapy. Recent radiographic data showed reduced hyperplastic adrenal nodules and testicular tumors. A diagnosis of TART should be considered and prioritized in CAH patients with testicular tumors. Replacement therapy using a sufficient amount of dexamethasone in this case helps combat TART.