No abstract

Transient neonatal tyrosinemia (TNT) is a form of hypertyrosinemia produced by the immaturity of 4-hydroxyphenylpyruvate dioxygenase (4-HPPD), a high intake of phenylalanine and tyrosine, and a relative ascorbic acid deficiency. Our objectives are to determine the incidence of TNT in Mexican newborns and to correlate it based on their sex, gestational age, and weight for gestational age to determine whether these are risk factors that predict the development of TNT. A cross-sectional descriptive study was conducted from January 2006 to August 2017. We analyzed 175 976 of newborn screening reports and found that the overall incidence of TNT was 1 (0.29%) in 342 newborns. It is more prevalent in preterm infants and in small for gestational age newborns (0.35%).The TNT incidence was determined in this Mexican population, and it was established as the most frequently occurring amino acid defect. We propose that pediatricians intentionally search for this pathology to offer patients access to adequate and timely treatment.

Introduction: CHDs are the most common type of birth defect. One in four newborns with a heart defect has a critical CHD. In Mexico, there is a lack of data available to determine its prevalence. Pulse oximetry screening programmes have been implemented worldwide, reporting opportunity areas in algorithm interpretation and data management. Our study aims to share preliminary results of a 3-year experience of a multicentre pulse oximetry screening programme that addresses critical challenges. Materials and methods: This retrospective study examined the reports of newborns screened from February 2016 to July 2019 from five hospitals. Two algorithms –the New Jersey and the American Academy of Pediatrics– were implemented over consecutive periods. The algorithms’ impact was assessed through the calculation of the false-positive rate in an eligible population. Results: A total of 8960 newborns were eligible for the study; from it, 32.27% were screened under the New Jersey and 67.72% under the American Academy of Pediatrics algorithm – false-positive rate: 1% (CI 95: ± 0.36%) and 0.71% (CI 95: ± 0.21%), respectively. Seventy-nine newborns were referred, six were diagnosed with critical CHD, and six with CHD. The critical CHD estimated prevalence was 6.69:10,000 newborns (CI 95: ± 5.36). Our results showed that the algorithm was not related to the observable false-positive rate reduction. Discussion: Other factors may play a role in decreasing the false-positive rate. Our experience implementing this programme was that a systematic screening process led to more confident results, newborn’s report interpretation, and follow-up.

Hawkinsinuria is an autosomal dominant disorder of tyrosine metabolism. Mutations in the 4-hydroxyphenylpyruvate dioxygenase gene ( HPD) result in an altered HPD enzyme, causing hawkinsin and tyrosine accumulation. Persistent metabolic acidosis and failure to thrive are common features in patients with hawkinsinuria. We present the first known Latin American patient diagnosed with hawkinsinuria, and the tenth reported patient in the literature. We aim to establish clinical practice guidelines for patients with hawkinsinuria. The patient’s plasma tyrosine level was 21.5 mg/dL, which is several times higher than the reference value. Mutation analysis indicated heterozygosity for V212M and A33T variants in HPD. In the case of altered tyrosine levels found during newborn screening, we propose exclusive breastmilk feeding supplemented with ascorbic acid. Amino acid quantification is useful for monitoring treatment response. If tyrosinemia persists, protein intake must be decreased via a low-tyrosine diet. Molecular studies can be used to confirm a patient’s disease etiology. Further reports are required to elucidate new pathogenic and phenotypic variations to enable the development of an appropriate therapeutic approach.

Screening for critical congenital heart disease is a clinical method used for their early detection using pulse oximetry technology. This, followed by a diagnostic confirmatory protocol, allows timely therapeutic interventions that improve the newborn’s outcome. According to Mexican birth statistics, approximately 18,000–21,000 neonates are born with a form of congenital heart disease each year, of which 25% are estimated to be critical congenital heart disease. We report two cases with an early critical congenital heart disease detection and intervention through an innovative critical congenital heart disease screening program implemented in two Mexican hospitals. They integrated a new automated pulse oximetry data analysis method and a comprehensive follow-up system (Cárdi-k®). Both cases were confirmed by echocardiogram, which served for an intervention in the first week of life, and the patients were discharged in good clinical condition. In addition, to the routine physical assessments, the critical congenital heart disease screening program (which includes echocardiogram for presumptive positive cases) should be implemented in a timely manner.