The mutational spectrum of the phenylalanine hydroxylase gene (PAH) in Mexico is unknown, although it has been suggested that PKU variants could have a differential geographical distribution. Genotype-phenotype correlations and genotype-based predictions of responsiveness to tetrahydrobiopterin (BH4 ) have never been performed. We sequenced the PAH gene and determined the geographic origin of each allele, mini-haplotype associated, genotype-phenotype correlations and genotype-based prediction of BH4 responsiveness in 48 Mexican patients. The mutational spectrum included 34 variants with c.60+5G>T being the most frequent (20.8%) and linked to haplotype 4.3 possibly because of a founder effect and/or genetic drift. Two new variants were found c.1A>T and c.969+6T>C. The genotype-phenotype correlation was concordant in 70.8%. The genotype-based prediction to BH4 -responsiveness was 41.7%, this information could be useful for the rational selection of candidates for BH4 testing and therapy.

ImportanceIt is currently unknown how often and in which ways a genetic diagnosis given to a patient with epilepsy is associated with clinical management and outcomes.ObjectiveTo evaluate how genetic diagnoses in patients with epilepsy are associated with clinical management and outcomes.Design, Setting, and ParticipantsThis was a retrospective cross-sectional study of patients referred for multigene panel testing between March 18, 2016, and August 3, 2020, with outcomes reported between May and November 2020. The study setting included a commercial genetic testing laboratory and multicenter clinical practices. Patients with epilepsy, regardless of sociodemographic features, who received a pathogenic/likely pathogenic (P/LP) variant were included in the study. Case report forms were completed by all health care professionals.ExposuresGenetic test results.Main Outcomes and MeasuresClinical management changes after a genetic diagnosis (ie, 1 P/LP variant in autosomal dominant and X-linked diseases; 2 P/LP variants in autosomal recessive diseases) and subsequent patient outcomes as reported by health care professionals on case report forms.ResultsAmong 418 patients, median (IQR) age at the time of testing was 4 (1-10) years, with an age range of 0 to 52 years, and 53.8% (n = 225) were female individuals. The mean (SD) time from a genetic test order to case report form completion was 595 (368) days (range, 27-1673 days). A genetic diagnosis was associated with changes in clinical management for 208 patients (49.8%) and usually (81.7% of the time) within 3 months of receiving the result. The most common clinical management changes were the addition of a new medication (78 [21.7%]), the initiation of medication (51 [14.2%]), the referral of a patient to a specialist (48 [13.4%]), vigilance for subclinical or extraneurological disease features (46 [12.8%]), and the cessation of a medication (42 [11.7%]). Among 167 patients with follow-up clinical information available (mean [SD] time, 584 [365] days), 125 (74.9%) reported positive outcomes, 108 (64.7%) reported reduction or elimination of seizures, 37 (22.2%) had decreases in the severity of other clinical signs, and 11 (6.6%) had reduced medication adverse effects. A few patients reported worsening of outcomes, including a decline in their condition (20 [12.0%]), increased seizure frequency (6 [3.6%]), and adverse medication effects (3 [1.8%]). No clinical management changes were reported for 178 patients (42.6%).Conclusions and RelevanceResults of this cross-sectional study suggest that genetic testing of individuals with epilepsy may be materially associated with clinical decision-making and improved patient outcomes.

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Objective To expose causes leading to the delayed arrival of phenylketonuria (PKU) patients at a governmental reference centre (RC), and to describe their clinical characteristics. Material and methods PKU files registered during the past 18 years at the National Institute of Pediatrics in Mexico City were evaluated. Patients were classified into two groups according to their age at arrival: Group I (early reference), patients arriving during the first month of life; and Group II (late reference), those who arrived after thirty days of age. Time and causes of delay were documented. Results Of 57 recorded files, 10 were classified in Group I and 47 in Group II. Causes leading to the late arrival of Group II patients were absence of routine newborn screening (NBS), PKU not included in the routine NBS, sampling after the recommended age, false negative result, results without interpretation and/or instructions to follow, delayed notification of results, poor medical criteria of attending physician, difficulties in obtaining confirmatory tests, and administrative failures. Conclusion The main cause of late referral of PKU patients was the absence of PKU testing. As a developing country, Mexico still faces challenges in the proper functioning and expansion of the NBS programme. Most PKU patients arrived at the RC late, presenting with varying degrees of the clinical spectrum. Incorporating PKU testing into the already established Mexican NBS system and adding quality indicators to guarantee proper operation in all NBS phases is necessary to achieve the goal of identifying, referring, diagnosing, and treating patients promptly.

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