Pterin Profiling in Serum, Dried Blood Spot, and Urine Samples Using LC-MS/MS in Patients with Inherited Hyperphenylalaninemia.

Background: Hyperphenylalaninemia (HPA) is defined as blood phenylalanine (Phe) levels exceeding the normal values (>120 µmol/L or >2 mg/dL) and is caused by a deficiency in the enzyme phenylalanine hydroxylase (PAH). The widespread screening of Phe levels in newborn screening programs has led to a very high number of patients with HPA. Methods: The samples were collected at various ages, not at the point of diagnosis. Nine pterin derivatives, including isoxanthopterin, sepiapterin, xanthopterin, primapterin, biopterin, neopterin, 7,8-dihydrobiopterin, 7,8-dihydroneopterin, and tetrahydrobiopterin (BH4), were analyzed in different HPA classes in serum, dried blood spots (DBS), and urine samples. A total of 18 patients, including six classical phenylketonuria (PKU), eight BH4-responsive PKU, and four mild HPA patients, were included in the study. Results: Among the nine pterin derivatives measured, a significant increase was observed in the levels of isoxanthopterin, biopterin, and 7,8-dihydrobiopterin in serum, dried blood spots (DBS), and urine samples of patients with HPA compared to the control group. However, elevations in isoxanthopterin, biopterin, and 7,8-dihydrobiopterin were observed in all HPA groups, although the extent of elevation varied among the different disease groups. There were also significant differences between HPA subgroups among these high values. Conclusion: In this study, it might be suggested that pterin profiling shows promising potential for its effective utilization in the differential diagnosis of HPA. Pterin profiling demonstrated its efficacy in accurately categorizing patients into distinct subtypes. This approach offers several notable advantages, including the ability to simultaneously screen multiple HPA subtypes through a single test, establish disease decision limits for pterins, shorten the time required for HPA differential diagnosis, reduce the risk of misdiagnosis, and increase overall diagnostic accuracy. This study is the most comprehensive study examining the association between HPA pterin in the literature. In our study, samples obtained from BH4-responsive PKU patients were on treatment. This may have affected the results. Preliminary findings on pterin profiles may need to be replicated in a prospective cohort of samples collected at the time of diagnosis to confirm the results.

ALG11-CDG: novel variant and review of the literature.

OBJECTIVES: Asparagine-dependent glycosylation 11-congenital disorders of glycosylation (ALG11-CDG) is a rare autosomal recessive N-glycosylation defect with multisystem involvement particularly neurological symptoms such as epilepsy and neuromotor developmental delay. CASE PRESENTATION: A 31-month-old male patient admitted to our center with complaints of axial hypotonia, drug-resistant myoclonic seizures, microcephaly and deafness. The electroencephalography (EEG) showed a burst-suppression pattern without hypsarrhythmia. Basal metabolic investigations were unremarkable. Progressive cerebral atrophy, hypomyelination and corpus callosum hypoplasia were striking features in brain MRI images taken during our follow-up. Compound heterozygous mutations of the ALG11 gene were found by whole exome sequencing (WES) analysis. It was determined that the c.476T>C mutation is a novel mutation. CDG type 1 pattern was detected with the examination of carbohydrate-deficient transferrin (CDT) by capillary zone electrophoresis. CONCLUSIONS: In patients with a possible congenital defect of glycosylation, a screening test such as CDT analysis is suggested. To discover novel mutations in this rare disease group, expanded genetic analysis should be performed.

Hypophosphatasia: is it an underdiagnosed disease even by expert physicians?

INTRODUCTION: Hypophosphatasia (HPP) is caused by mutations in the ALPL that encodes the tissue-nonspecific isoenzyme of alkaline phosphatase (ALP). Clinical manifestations range from extreme life-threatening lethal forms to no signs or symptoms at all. MATERIALS AND METHODS: Consecutive 30,000 outpatients and inpatients with ALP data were screened retrospectively, out of which 1000 patients were found to have low levels of ALP more than once. Then, patients were evaluated for the symptoms and signs of HPP with further biochemical and genetic analyses. RESULTS: Thirty-seven patients who had severe musculoskeletal pain, recurrent fractures, and tooth anomalies were then screened with substrate and DNA sequencing analyses for HPP. It was determined that eight patients had variants in the ALPL gene. A total of eight different ALPL variants were identified in eight patients. The variants, namely c.244G > C (p.Gly82Arg), c.1444C > T (p.His482Tyr), c.1487A > G (p.Asn493Ser), and c.675_676insCA (p.Met226GlnfsTer52), had not been previously reported. DISCUSSION: Considering the wide spectrum of clinical signs and symptoms, HPP should be among the differential lists of bone, muscle, and tooth abnormalities at any age.