Pablo Ramírez

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 four 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: Five individuals (four 46,XY; one 46,XX) from four 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 (Conclusions: 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.

Congenital adrenal hyperplasia (CAH) is an autosomal recessive disorder caused by a deficiency of enzymes involved in cortisol biosynthesis. More than 90% of the cases are due to 21-hydroxilase deficiency. This leads to the accumulation of 17-hydroxyprogesterone (17OHP) and allows diagnosis of this disorder in newborn screening (NS) programs. Premature newborns typically have higher levels than full-term newborns, making the use of age-appropriate cut-off values important for accurate interpretation. The aim of our study was to update the gestational age-adjusted cut-off values for 17OHP, the methodology currently used in Argentina by the jurisdictions participating in the National Program for the Strengthening of Early Detection of Congenital Diseases. Cut-off limits were obtained using percentiles of the distribution of 17OHP values for each gestational age on 53,230 dry blood spot (DBS) samples. Sensitivity, specificity, false positive rate, positive predictive value, and incidence were calculated. We successfully established gestational age-specific cut-off values for 17OHP. The analysis showed a sensitivity of 100%, specificity of 99.52%, a false positive rate of 0.49%, and a positive predictive value of 1.54%. The incidence of CAH was 1:13,308 live births. These findings underscore the importance of using population-appropriate cut-off limits. Such harmonization enables comparability among regional neonatal screening programs with the added benefit of decreasing the rate of recalls and associated costs.

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.

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.