Hyperphenylalaninemia

Hyperphenylalaninemia (HPA) is caused by a deficiency of phenylalanine hydroxylase (PAH) or a deficiency of its coenzyme tetrahydrobiopterin (BH4), resulting in blood phenylalanine ( Phenylalanine, Phe) is a group of the most common amino acid metabolic diseases. With the development of disease diagnosis, differential diagnosis, treatment, neonatal screening and prevention technology, HPA has become a treatable and preventable disease, and is a model for the history of prevention and treatment of genetic metabolic diseases [1-3]. China began HPA screening and treatment research in 1981. In the past 33 years, the national screening rate has been gradually improved [4-6]. The diagnosis of most HPA children from the diagnosis of clinical symptoms is to the asymptomatic biochemistry and genes of newborns. Diagnostic changes, early screening, differential diagnosis, and proper treatment of HPA are becoming new challenges for clinicians. To this end, according to the Ministry of Health "Phenylketonuria and congenital hypothyroidism diagnosis and treatment of technical specifications" [7], with reference to domestic and foreign experience and guidelines [8-10], Chinese Medical Association Pediatric Branch Endocrine Genetic Metabolism Group and The Newborn Screening Group of the Chinese Society of Preventive Medicine's Birth Defect Prevention and Control Committee discussed the diagnosis and treatment of HPA and proposed the following consensus. Overview 1.1 Definition of HPA Blood Phe concentration > 120 μmol/L (> 2 mg/dl) and blood Phe to Tyrosine (Tyr) ratio (Phe/Tyr) > 2.0 are collectively referred to as HPA [8-10]. 1.2 Causes and classification of HPA The causes of HPA are divided into PAH deficiency and BH4 deficiency, both of which are autosomal recessive diseases [1,9,11]. PAH deficiency: Children with varying degrees of HPA due to PAH deficiency (Figure 1). It is usually classified according to the highest blood Phe concentration before treatment or the natural protein intake sufficient for blood Phe concentration. Classical phenylketonuria (PKU): blood Phe ≥ 1 200 μmol / L; mild PKU: blood Phe 360 ~ 1200 μmoI / L; mild HPA: blood Phe 120 ~ 360 μmoI / L [1, 11 ]. Foreign countries also classify dietary Phe tolerance according to 2~5 years old. Children with classic PKU, mild PKU and mild HPA** have a tolerance to Phe <20 20=” 50=”” kg ="" > 50 mg / (kg · d) [1,8], but the need for standardized post-diet assessment, clinical practical application is complex. Read more...