Natalia Perez Garrido

Background/Objective: DICER1 ‐related tumor predisposition is a rare hereditary tumor predisposition disorder characterized by autosomal dominant inheritance, reduced penetrance, and variable expressivity. This study is aimed at describing the clinical and molecular spectrum of DICER1 ‐related tumor predisposition in an Argentine pediatric cohort. Design and Methods: Seventeen unrelated patients with DICER1 ‐related tumor predisposition and 54 relatives were evaluated at “Prof. Dr. J. P. Garrahan” Pediatric Hospital (Buenos Aires, Argentina) between 2014 and 2024. Germline and somatic DICER1 variants were analyzed using Sanger or next‐generation sequencing. Functional assays were performed for selected intronic variants. Three samples of poorly differentiated thyroid carcinoma were also included. Results: Sixteen distinct germline variants were identified in the 17 index cases, including 12 novel alterations (75%). One quarter of the variants were de novo. Thyroid involvement, particularly multinodular goiter and papillary thyroid carcinoma, was the most common presentation and frequently coexisted with ovarian Sertoli–Leydig cell tumors or embryonal rhabdomyosarcoma. Two novel intronic variants were confirmed to affect splicing by RT‐PCR. Somatic “hotspot” mutations in exons 24–25 (RNase IIIb domain) were detected in most tumors, consistent with the two‐hit model. The identification of asymptomatic carriers enabled early surveillance and preventive interventions. Conclusions: This study expands the molecular spectrum of germline DICER1 variants, reinforces the predominance of thyroid involvement, and highlights the value of molecular testing for diagnosis, genetic counseling, and early intervention. Ethical considerations regarding surveillance and management of asymptomatic carriers remain an important area in need of future guidance.

Context: P450 oxidoreductase (POR) deficiency is a rare congenital adrenal hyperplasia with variable severity. The mechanisms of severe mutations and their full metabolic consequences, including drug metabolism, are not fully characterized. Objective: To define the clinical, biochemical, and molecular consequences of a novel homozygous POR missense mutation, p.Gly88Ser (G88S), identified in 4 unrelated Argentine families. Design: A translational study combining clinical case series analysis with comprehensive in vitro molecular and functional characterization of the novel protein variant. Setting: Tertiary pediatric endocrine centers in Argentina and Switzerland. Patients: We report 5 individuals (4 46,XY; 1 46,XX) from 4 unrelated families presenting with disorders of sex development and adrenal dysfunction. Main Outcome Measures: Clinical phenotypes, hormonal profiles, and POR gene sequencing. In vitro analysis of recombinant POR measured flavin content, reductase activity, and support of steroidogenic and drug-metabolizing P450s. Results: All patients were homozygous for the c.262G>A (p.G88S) mutation. This FMN binding domain variant caused protein instability with severe loss of FMN (<30%) and FAD (<15%) cofactors. Steroidogenic activities were virtually abolished (CYP21A2: 1.3%; CYP17A1 17,20-lyase: 5.5% of wild-type), explaining the clinical phenotype. Activities of major drug-metabolizing enzymes were also severely impaired (3%-9% of wild-type), establishing a “poor metabolizer” phenotype. Conclusion: The POR G88S mutation causes one of the most severe forms of PORD described, driven by dynamic protein instability and cofactor loss. It is a critical pharmacogenomic marker, and its recurrence in Argentina suggests a potential screening target.

Introduction: In children, papillary thyroid cancer (PTC) is generally sporadic and may, less frequently, be part of an undiagnosed hereditary tumor predisposition syndrome (HTPS). Somatic molecular testing is useful to understand tumor etiology and behavior, predict prognosis, and possibly guide development of novel treatment strategies. The aims of our study were to analyze the findings of a next-generation sequencing (NGS) panel in a cohort of pediatric PTC from Argentina according to age at presentation, recurrence risk, and response to treatment. Methods: A retrospective descriptive study was conducted of 63 consecutive pediatric patients with PTC seen at a single center in whom a DNA-based NGS panel was performed. The patients were classified according to the ATA-2015 recurrence risk stratification into a low (n = 10), an intermediate (n = 13), and a high-risk group (n = 40). All patients were treated with total thyroidectomy and radioiodine. At the last follow-up, patients were classified as excellent response (ER) or having persistent disease (PD). Results: In 70% (44/63) of the samples, a pathogenic somatic variant was detected; the most frequent alterations were RET fusions (20%). Fusions were more frequent in younger patients (median age 11.45 vs. 13.7 years; p = 0.048), in diffuse sclerosing subtype histology (p = 0.01) and in the high-recurrence risk group (p < 0.014). The risk of PD was higher in patients in the high-risk group (odds ratio, 9.2). When evaluating treatment response based on molecular findings, we found that among the 25 patients who achieved ER, 12 (48%) had fusions and 13 (52%) had point variants, with no statistically significant difference. However, among the 19 patients with PD, 12 (64%) had fusions and 7 (36%) had point variants, a difference that was statistically significant (p < 0.01). In 5/63 (8%), pathological germline mutations were observed in genes associated with HTPSs: DICER1 (n = 2), PTEN (n = 1), and MSH6 (n = 2). Conclusions: Interestingly, in our PTC cohort, the NGS panel was highly specific to detect molecular alterations. Fusions were more frequent at a younger age and in the ATA-2015 high-recurrence-risk group; however, it was not a determining factor to predict PTC outcome. Finally, detection of pathological germline mutations in genes involved in HTPS was useful for genetic counseling.

Background: 46,XX testicular/ovotesticular disorders of sexual development (T/OT DSD) are infrequent congenital conditions characterized by the presence of functional ovarian and testicular or only testicular parenchyma. Objective: The aim of the study was to retrospectively describe clinical, hormonal, and genetic characteristics of 29 patients with 46,XX T/OT DSD (2000–2023), focusing on gonadal function, hormonal production, and long-term follow-up. Results: Most patients (n = 25, 86.2%) presented with atypical genitalia that suggested DSD. Median age at first assessment was 0.38 years. Sex assignment was male in 21 patients without reports of discordant gender identity. Sex assignment was recommended before expert evaluation and without adequate studies in 64% of those patients with atypical genitalia (16/25). The median external masculinization score was 8 (range 4–12). During mini-puberty, LH, testosterone, AMH, and the LH/FSH ratio were above the female reference range and no different from the normal male reference range. Spontaneous puberty was observed in one female and 10 male-assigned subjects. Among the latter, pubertal virilization occurred with signs of hypergonadotropic hypogonadism and gynecomastia. Molecular studies identified the underlying mechanism in 7 patients: SRY gene was identified in two, WT1 gene variations were detected in three others, and 2 syndromic patients harbored complex chromosomal rearrangements. Conclusion: Our findings underscore the clinical and biochemical variability in 46,XX T/OT DSD. Expert evaluation and accurate diagnostic work-up are essential prior to sex assignment and to prevent misdiagnosis and inappropriate treatments. Mini-puberty was characterized by a masculinized pattern of gonadotropin secretion. The potential for functional male pubertal development should be taken into account when making sex assignment decisions.

Introduction: Associated conditions, especially being born small for gestational age (SGA), have been reported with a higher prevalence in patients with differences in sexual development (DSD) compared to the general population. Our objective was to analyze the prevalence of SGA in a cohort of DSD patients evaluated at a single tertiary pediatric center, and to examine its association with sex chromosome constitution, molecular diagnosis, and clinical phenotype. Methods: Gestational age, birth weight, and birth length were evaluated to assess prenatal growth and the prevalence of SGA. DSD patients were classified according to karyotype. Among 46,XY DSD patients, perinatal data were further analyzed based on molecular diagnosis and the presence or absence of gonadal dysgenesis. Results: Overall, 642 DSD patients were included: 202 (31.5%) with chromosomal DSD, 218 (33.9%) with 46,XX DSD, and 222 (34.6%) with 46,XY DSD. SGA prevalence was 30.2%, 7%, and 27.5%, respectively. In the 46,XY DSD group, a molecular diagnosis was achieved in 35% of patients. SGA was more frequent in 46,XY DSD subjects without molecular diagnosis and without gonadal dysgenesis. Conclusion: A high prevalence of SGA was observed among individuals with sex chromosome DSD, consistent with the literature, whereas a lower prevalence was found among those with 46,XX DSD, as expected in the Latin American population. The frequency of SGA in the 46,XY DSD group reinforces the association between SGA and DSD in the 46,XY DSD, particularly in patients without a clear molecular diagnosis and without specific disorders of undervirilization. Factors involved in early embryonic growth, development, and gonadal differentiation may mediate the association between being born SGA and DSD in humans. Further studies are needed to clarify the etiological diagnosis.

Background: Persistent müllerian duct syndrome (PMDS) is characterized by the persistence of müllerian duct derivatives in otherwise normally virilized 46,XY males. Biallelic mutations of the anti-müllerian hormone (AMH) and AMH receptor type 2 (AMHR2) genes lead to PMDS type 1 and 2, respectively. Aim: The aims of the study were to report the clinical, hormonal, and genetic findings in a patient with PMDS and discuss surgical strategies to achieve successful orchidopexy. Results: A 4-year-old boy was evaluated after the incidental finding of müllerian derivates during laparoscopy for nonpalpable gonads. Karyotype was 46,XY and laboratory tests revealed normal serum gonadotropin and androgen levels but undetectable serum AMH levels. PMDS was suspected. Molecular analysis revealed a novel variant c.902_929del in exon 5 and a previously reported mutation (c.367C>T) in exon 1 of the AMH gene. Successful orchidopexy was performed in two sequential surgeries in which the müllerian duct structure was preserved and divided to protect the vascular supply to the gonads. Histological evaluation of the testicular biopsy showed mild signs of dysgenesis. Doppler ultrasound showed blood flow in both testes positioned in the scrotum 1.5 years after surgery. Conclusion: PMDS is a rare entity that requires a high index of suspicion (from surgeons) when evaluating a patient with bilateral cryptorchidism. Surgical treatment is challenging and long-term follow-up is essential. Histological evaluation of the testis deserves further investigation.

Purpose Patients with hereditary hypophosphatemic rickets are short and disproportionate and very little information is available on segmental growth, but the body disproportion at adulthood leads us to think that the growth velocity of legs is slower. Methods A total of 96 children were included and molecular testing was carried out in 42. Children who reached adult height were classified into two groups according to their compliance to conventional treatment (phosphate supplement and calcitriol). Individual growth records of height and sitting height/height were plotted using Argentine reference data in 96 children and growth curves were estimated by fitting Preece-Baines Model 1 in 19 of the children. Results Molecular testing revealed sequence deleterious alterations or large deletions in 36/42 patients. During childhood, 76% of children grew below − 1.88 standard deviation score (SDS) and 97% had body disproportion. During adolescence, the mean peak height velocity for the good and poor compliance to treatment groups was 7.8 (0.6) and 5.4 (0.4) cm/year in boys and 7.0 (0.7) and 5.2 (0.8) cm/year in girls, respectively. At adulthood, the median sitting height/height ratio was 2.32 and 6.21 SDS for the good and poor compliance to treatment groups, respectively. The mean pubertal growth spurt of the trunk was –0.8 (1.4) SDS, with a short pubertal growth spurt of − 1.8 (0.4) SDS for limbs in the good compliance group. Median adult height in 13/29 males and 30/67 females was –4.56 and –3.16 SDS, respectively. Conclusion For all patients the growth spurt was slower, secondary to a short growth spurt of limbs, reaching a short adult height with body disproportion that was more prominent in the poor compliance group.

Significance: Sex development involves a precise spatiotemporal expression and interactions of numerous genetic factors, including the WT1 (Wilms tumor 1) gene. Complete and partial loss-of-function WT1 variants are associated with 46,XY disorders/differences of sex development (DSD). Some 46,XX individuals develop testis in absence of the testis-determining gene SRY . We describe a genotype/phenotype association where variants impacting the C-terminal zinc finger (ZF4) of WT1 cause testis development in 46,XX individuals. XX mice carrying a pathogenic variant of ZF4 display masculinization of the fetal gonads. Testis formation may be due to inappropriate interaction between the mutated WT1 and an essential ovarian determinant β-CATENIN. These data show that variants affecting a specific domain of a developmental transcription factor can switch organ fate.

The aim of this study was the molecular characterization of the AR gene as the cause of 46,XY disorder in our population. We studied 41, non related, 46,XY disorder of sexual differentiation index cases, having characteristics consistent with androgen insensivity syndrome (AIS). Genomic DNA was isolated from peripheral blood leukocytes of all patients and 25 family members from 17 non-related families. The AR gene analysis revealed an abnormal sequence in 58.5% of the index patients. All of the complete AIS (CAIS) cases were genetically confirmed, while in the partial form (PAIS) a mutation in AR was detected in only 13 (43.3%). Molecular studies revealed other affected or carrier relatives in 87% of the index cases. The AR mutations were found spread along the whole coding sequence, with a higher prevalence in the ligand binding domain. Nine out of 23 (39%) AR mutations were novel. In 17% of patients with detected AR mutations, somatic mosaicism was detected in leucocyte DNA. In our cohort, long-term follow up gender dysphoria, raised as male or female, was not found. Finally, in suspected PAIS, the identification of AR mutation occurred significantly less than in CAIS patients. Improved knowledge of the components of the AR complex and signaling network might contribute to long term outcome and genetic counseling in AIS patients.