Identifying 17-β-HSD3 Deficiency in Patients with Karyotype 46,XY Misdiagnosed with Androgen Insensitivity Syndrome: A Pediatric Case Report

Introduction

Disorders of sex development (DSD) include a spectrum of disorders in which chromosomal, genetic, gonadal, hormonal, or anatomic aspects of sex are atypical [1]. The incidence is estimated at 1 in 20 000 live births for 46,XY DSDs and 1 in 14 000–15 000 for 46,XX DSDs, most commonly due to congenital adrenal hyperplasia [2,3]. DSDs are classified into sex chromosome, 46,XX, and 46,XY categories [4]. Causes of 46,XY DSD include gonadal dysgenesis, androgen biosynthesis defects (eg, 17 beta-hydroxysteroid dehydrogenase type 3 (17β-HSD3) deficiency), and androgen insensitivity syndrome (AIS) [4,5]. Diagnosis requires a multidisciplinary approach involving clinical, hormonal, imaging, and genetic assessments [3]. Management is individualized, addressing gender identity, malignancy risk, and hormone therapy [5].

Synthesis of sex steroids is controlled by multiple enzymes, which include 17-β-HSD3 [4]. 17-β-HSD3 is inherited as an autosomal recessive trait on chromosome 9q22.32 and expressed in the testes. In the testes, 17-β-HSD3 converts inactive steroid androstenedione to active testosterone [6].

In males, homozygous or compound heterozygous mutations of 17-β-HSD3 result in a decrease of testicular testosterone and subsequently decreases the dihydrotestosterone level. The disorder manifests as under-masculinization, which is characterized by hypoplastic-to-normal internal male genitalia with an external female phenotype [4]. Therefore, the pathognomonic hallmark of this disorder is a decreased plasma testosterone-to-androstenedione ratio (T: A) [7]. However, homozygous or compound-heterozygous mutations in females are asymptomatic [8].

As male patients have normal anti-Mullerian hormone secretion, they lack Mullerian structures (uterus, fallopian tubes, cervix, and the upper two-thirds of the vagina), whereas Wolffian derivatives (epididymis, vas deferens, and seminal vesicles) are often normally developed and the testes are located in the inguinal canal. These patients are usually assigned as females and reared as such because female external genitalia are common at birth [6]. At puberty, a significant amount of circulating androstenedione is converted to testosterone in peripheral tissues by an unidentified member of the 17-β-HSD3 isozyme family [9]. This acts as a partial compensatory mechanism, which explains the late-onset virilization despite the enzymatic deficiency. Thereby, it results in virilization, which can lead to an incorrect diagnosis of AIS [7]. AIS is an X-linked recessive disorder of androgen action. It is manifested as female external genitalia, absence of Mullerian duct derivatives, sparse sexual hair, inguinal masses, and primary amenorrhea in adolescent females [10].

In the literature, 191 families (244 patients) have been reported to have 17-β-HSD3 deficiency with a total of 74 different 17-β-HSD3 mutations [7,11]. To date, this is the second case reported in the literature from Saudi Arabia, as the first was reported as a case series of 3 family members with different mutations [12]. The findings of the study indicated the molecular basis of DSD in the Arab population. The authors described the molecular genetics of a relatively large cohort of DSD cases from the highly consanguineous population of Saudi Arabia [12]. Such cases would expand the literature on DSD, and it would highlight a potential founder mutation in this region. This report describes the case of a 13-year-old phenotypic female with 46,XY karyotype and a history of virilization due to 17-β-HSD3 deficiency, who was previously diagnosed with AIS.

Case Report

We report the case of a 13-year-old phenotypic female who was initially diagnosed with AIS during early childhood at a rural hospital. Medical records from that facility indicate that during infancy, she underwent inguinal hernia repair, during which a unilateral inguinal gonad was identified, while the contralateral gonad was not found. As a result, a unilateral orchiectomy was performed. Karyotyping was ordered, which revealed 46,XY chromosomes. Consequently, the family was informed that the missing gonad would atrophy, and the patient was diagnosed with AIS.

Several years later, she presented to the pediatric endocrinology clinic at a tertiary hospital with progressive signs of virilization over the preceding months, including hirsutism, voice deepening, and severe facial acne. Physical examination showed signs of virilization in addition to clitoromegaly and a palpable left inguinal gonad. Repeated karyotyping confirmed 46,XY chromosomes.

Additionally, pelvic ultrasonography revealed the absence of a uterus and ovaries. Moreover, pelvic magnetic resonance imaging (MRI) showed absence of prostate tissue, uterus, and ovaries, but bilateral oval-shaped structures in the inguinal area were found. The shape and the signal intensity were highly suggestive of testicular structures. The absence of prostate tissue in patients with 46,XY with 17-β-HSD3 deficiency is a crucial diagnostic feature that assists in differentiating this condition from other DSDs, such as AIS, in which the presence of prostate tissue can be present [4].

Laboratory investigations revealed a pubertal level of follicle-stimulating hormone (FSH) 8.78 mIU/ml (2.5–4.5 mIU/mL mIU/mL) and luteinizing hormone (LH) (22.14 mIU/ml, reference range 2.5–3.0 mIU/mL). The total testosterone level was 2.17 ng/ml (reference range 0.11–0.66), Free testosterone level was 0.21 ng/dL (reference range 0.086–1.329) ng/dL and estradiol level was 127 pg/ml (reference range 15–40) pg/ml.

Furthermore, human chorionic gonadotropin (HCG)-stimulation testing showed a basal testosterone level of 2.1 ng/ml and a basal androstenedione level of 22.4 ng/ml(reference range 0.5–2.0) ng/ml. A post-HCG stimulation test was performed with 1500 IU given daily for 3 days, which increased testosterone level to 2.8 ng/ml and androstenedione to 25.6 ng/ml, with a T: A ratio of 0.1, suggestive of 17-β-HSD3 deficiency, as the cut-off point to diagnose 17-β-HSD3 deficiency is less than 0.8. This ratio serves as a biochemical hallmark for the disorder, as the enzyme defect impairs conversion of androstenedione to testosterone in the testes, leading to a characteristically low T: A ratio. A persistently low T: A ratio distinguishes 17β-HSD3 deficiency from other causes of 46,XY under-virilization, such as AIS, in which testosterone production is normal or elevated [5]. Testicular histopathology was not available and the procedure was not performed.

Whole-exome sequence testing showed homozygous of uncertain significance variant in the HSD17B3 gene with missense variation in exon 4. (NM_000197.1: c.359T>A;P.Leu120His), as illustrated in Figure 1, which replaces amino acid leucine with histidine at codon 120. This variant has not been previously reported in the literature.

As the patient had been raised as a female, the parents maintained the female gender assignment. Subsequently, she underwent bilateral orchiectomy along with clitoroplasty and labioplasty at another medical center.

Discussion

This report describes the case of a 13-year-old phenotypic female with 46,XY karyotype and a history of virilization due to 17-β-HSD3 deficiency, previously diagnosed with AIS. This case highlights the diagnostic complexity of 46,XY DSDs and underscores the importance of re-evaluating early diagnoses, such as AIS, when new clinical signs (eg, progressive virilization) emerge during adolescence. It also emphasizes the critical role of early referral to a pediatric endocrinologist, particularly in cases with ambiguous genitalia or inguinal gonads, to ensure timely hormonal evaluation, genetic testing, and appropriate gender assignment.

17βHSD3 deficiency is the third most common cause of non-dysgenetic 46,XY DSD worldwide [13]. Studies have reported a prevalence of 0–6.8% [14–16]. Specifically, in Arab populations, 17βHSD3 and 5-α reductase deficiencies are the second most common causes of DSDs [12]. The occurrence of this disorder is significantly influenced by the rates of consanguinity [4], and our patient’s parents were first-degree relatives.

Our patient was a 13-year-old raised as a female, who presented with progressive virilization during adolescence. Although initially diagnosed with AIS, a low testosterone-to-androstenedione (T/AND) ratio (0.1) following hCG stimulation, along with a homozygous missense variant in the HSD17B3 gene, supported the diagnosis of 17β-HSD3 deficiency [11]. Among similar previously reported cases, several patients were raised as females, presented with typical or mildly ambiguous genitalia, and developed virilization during or before puberty, leading to gender reassignment and testosterone therapy. In all cases, a low T/AND ratio was critical for diagnosis, with hCG stimulation testing required in prepubertal patients. Unlike those patients, our case was not reassigned but underscores the importance of re-evaluating early DSD diagnoses when new clinical signs emerge. Similarly, there was a report of C268Y substitution mutation in a person with 46,XY raised as female who presented with virilization and was diagnosed with 17β-HSD3 deficiency, confirmed by a low T/AND ratio and molecular analysis [7].

Clinical presentations of 46,XY 17βHSD3 deficiency range from normal female external genitalia to various degrees of ambiguous genitalia, similar to our patient, who presented with normal female external genitalia [4,17,18]; the internal organs lacked Mullerian structures, but Wolffian derivatives are frequently normal, and the testes are located in the inguinal canal, as in our patient.

As female external genitalia are common at birth, these newborns are usually assigned as females and raised as such [4,17,18], which is similar to our case. Such presentation is due to severe intrauterine testosterone deficit [4]. However, a systematic review reported that half of the patients were initially raised as males, perhaps due to the presence of ambiguous genitalia at birth [13]. The Global DSD Update Consortium recommended infants diagnosed with 17βHSD3 deficiencies should be raised as males, as most such patients are thought to have a male gender identity and demand a change in male gender roles [19]. However, our patient’s parents decided to keep the female gender assignment.

The diagnostic approach to gender identity involves comprehensive and multidisciplinary assessments to evaluate the patient’s readiness before initiating any medical intervention. The treating team should consider gonadal function, as well as psychological and social factors (eg, family support, cultural context, and lived gender experience) [4]. These factors are critical in shaping and affirming the patient’s gender identity. A holistic assessment ensures that both biological and psychosocial elements guide clinical decision-making [1]. Despite the confirmed diagnosis of 17β-HSD3 deficiency and the presence of a 46,XY karyotype, our patient’s parents elected to maintain the female gender assignment, considering the patient’s upbringing, psychosocial factors, and their personal and cultural considerations.

The diagnostic confusion between 17β-HSD3 deficiency and AIS can be attributed to the significant phenotypic overlap between these 2 conditions [5]. Differentiating between these disorders can be facilitated by measuring the basal and hCG-stimulated levels of sex hormones, their precursors, and metabolites [5]. Further, molecular genetic tests could be utilized to provide a definite diagnosis [20–22].

Nevertheless, limited availability of pediatric endocrinology services and advanced laboratory testing in rural settings can lead to an incorrect initial diagnosis, as in this case.

Early childhood diagnosis could have been made by a specialized pediatric endocrinologist, as these patients can have a mild clitoromegaly, urogenital sinus, or inguinal hernia, with testes along the inguinal canals or labioscrotal folds [4,17,18]. Severe virilization typically happens at during puberty [9,23], as in this case.

Conclusions

Given the overlapping clinical features of various DSDs, differentiation can be challenging and can lead to diagnostic uncertainty. This case highlights the critical role of genetic and hormonal testing, as well as the importance of early referral to a specialized pediatric endocrinologist for timely and appropriate diagnosis and management.