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Background: Information regarding the prevalence of PKU in the Middle East in comparison to other world regions is scarce, which might be explained by difficulties in the implementation of national newborn screening programs., Objective: This study seeks for the first time to genotype and biochemically characterize patients diagnosed with hyperphenylalaninemia (HPA) at the Pediatric Metabolic Genetics Clinic at the King Hussein Medical Center, Amman, Jordan., Methods: A total of 33 patients with HPA and 55 family members were investigated for pterins (neopterin and biopterin) and dihydropteridine reductase (DHPR) activity in dried blood spots. Patients with HPA were genotyped for phenylketonuria (PKU) and the genes involved in tetrahydrobiopterin (BH 4 ) metabolism., Results: In total 20 patients were diagnosed with PKU due to phenylalanine hydroxylase (PAH) deficiency, 2 with GTP cyclohydrolase I (GTPCH) deficiency, 6 with DHPR deficiency, and 3 with the 6-pyruvoyl-tetrahydropterin synthase (PTPS) deficiency. Diagnosis was not possible in 2 patients. This study documents a high percentage of BH 4 deficiencies within HPA patients. With one exception, all patients were homozygous for particular gene variants., Conclusions: This approach enables differentiation between PKU and BH 4 deficiencies and, thus, allows for critical selection of a specific treatment strategies., Competing Interests: The authors declare no conflicts of interest., (© 2020 The Authors. Journal of Inherited Metabolic Disease published by John Wiley & Sons Ltd on behalf of SSIEM.)

Two sisters were diagnosed in their adulthood with aromatic L-amino acid decarboxylase (AADC) deficiency (OMIM#608643). They experienced early myasthenia-like manifestations, myoclonic jerks, oculogyric crises, tremors, and developmental delay during childhood; clinical stabilization afterwards; and spontaneous improvement during adolescence and young adulthood. Two novel pathogenic mutations on DDC gene [p.Tyr37Thrfs*5 (c.105delC) and p.F237S (c.710 T>C)] were associated with undetectable enzyme activity in plasma and only a mild reduction of biogenic amines in cerebrospinal fluid (CSF). The increase of both 3-O-methyldopa and 5-hydroxytryptophan on CSF was the most relevant biochemical alteration denoting AADC defect in these subjects. Transdermal rotigotine remarkably improved their gross motor functions and the asthenic status they complained. The present cases broaden the phenotypic spectrum of AADC deficiency and suggest that (1) AADC defect is not a progressive neurological disease and behaves rather as a neurodevelopmental disorder that improves during the second decade of life; (2) treatment-naïve adults can still respond well to neurotransmitter therapy; and (3) the possibility of a mild presentation of AADC deficiency should be considered when examining young adults with asthenic and parkinsonian symptoms.