Correct Answer: B. Ovotestis is seen in the gonadal biopsy
Ovotesticular disorder of sex development (OT-DSD), formerly called true hermaphroditism, is defined by the simultaneous presence of both ovarian and testicular tissue in the same individual. This is the pathognomonic histological finding that distinguishes OT-DSD from other DSDs. Gonadal biopsy or histopathology is the gold standard diagnostic tool that reveals the characteristic ovotestis—a single gonad containing both functional ovarian follicles and seminiferous tubules. This mixed gonadal tissue may be arranged as a true ovotestis (both tissues in one gonad) or as separate ovary and testis. The diagnosis cannot be made clinically or biochemically alone; histological confirmation is essential. In Indian pediatric practice, when a DSD case presents with ambiguous genitalia and unclear gonadal anatomy on imaging, gonadal biopsy becomes the definitive diagnostic modality. The presence of ovotesticular tissue fundamentally defines the condition and guides management regarding gonadectomy decisions and hormone replacement therapy. This is the discriminating feature that makes option B the only true statement about OT-DSD pathology.
Why the other options are wrong
A. Karyotype is 46 XY. — This is incorrect because OT-DSD shows variable karyotypes, not exclusively 46,XY. While 46,XY is the most common (approximately 50–60% of cases), OT-DSD also occurs with 46,XX (20–30%), 45,X/46,XY mosaicism, and other mosaic patterns. The karyotype is not a defining feature; the histological presence of both ovarian and testicular tissue is. NBE may trap students who memorize '46,XY = male' without understanding that DSD karyotypes are heterogeneous. C. Uterus is usually absent. — This is false. In OT-DSD, the uterus is usually present because müllerian duct development depends on the absence of anti-müllerian hormone (AMH) from testicular tissue, and the presence of ovarian tissue does not suppress müllerian development. Many OT-DSD individuals have a functional or partially functional uterus. The absence of uterus is characteristic of 46,XY DSD with complete testicular development, not OT-DSD. This option confuses OT-DSD with other forms of XY DSD. D. The response of testosterone to hCG is increased. — This is incorrect. In OT-DSD, the testosterone response to hCG stimulation is typically normal or blunted, not increased, because the testicular component may be dysgenetic or functionally immature. Increased hCG-stimulated testosterone is seen in conditions like androgen insensitivity syndrome (where Leydig cells are hyperresponsive) or in 46,XY DSD with Leydig cell hyperplasia, not in OT-DSD. This option misapplies endocrine findings from other DSDs.
High-Yield Facts
- Ovotestis (both ovarian and testicular tissue in same gonad) is the pathognomonic histological finding that defines OT-DSD and requires gonadal biopsy for diagnosis.
- Karyotype in OT-DSD is variable: 46,XY (50–60%), 46,XX (20–30%), and mosaics (45,X/46,XY, 46,XX/46,XY); karyotype alone does NOT define the condition.
- Müllerian ducts are usually present in OT-DSD because ovarian tissue does not produce AMH; uterus and fallopian tubes are typically retained.
- Gonadal biopsy is the gold standard diagnostic test for OT-DSD; imaging (ultrasound, MRI) cannot reliably distinguish ovotestis from other gonadal dysgenesis.
- Management of OT-DSD involves gonadectomy of dysgenetic/non-functional gonad and hormone replacement; fertility depends on location and function of retained gonadal tissue.
Mnemonics
OT-DSD = Both Tissues Ovotesticular = Ovary + Testis in same gonad. Diagnosis = Biopsy shows both. Karyotype = Variable (not fixed). Uterus = Usually present (ovary doesn't block müllerian ducts). DSD Diagnosis Hierarchy Karyotype tells sex chromosome status (not gonadal tissue). Imaging shows gonad location/size. Biopsy shows actual tissue type (ovary, testis, ovotestis). For OT-DSD: biopsy is diagnostic.
NBE Trap
NBE pairs 'karyotype 46,XY' with DSD to lure students into thinking a single karyotype defines the condition. In OT-DSD, karyotype is heterogeneous; the tissue composition (ovotestis on biopsy) is the defining diagnostic criterion, not chromosomes.
Clinical Pearl
In Indian pediatric centers, a neonate with ambiguous genitalia and unclear gonadal anatomy on ultrasound should undergo gonadal biopsy (or diagnostic laparoscopy with biopsy) to confirm OT-DSD before deciding on gonadectomy. Preserving functional ovarian tissue in 46,XX OT-DSD cases may allow future fertility with hormone support—a key counseling point for families.
_Reference: OP Ghai Pediatrics Ch. 8 (Disorders of Sex Development); Robbins Pathology Ch. 24 (Reproductive System)_