Possible high frequency of tetrahydrobiopterin deficiency in south Brazil.
We report our experience with the deficiency of 6-pyruvoyltetrahydropterin synthase, the most common form of tetrahydrobiopterin deficiency. We investigated 5200 patients suspected of having some inborn error of metabolism in a 10-year period, and detected 30 cases (from 28 sibships) of hyperphenylalaninaemias, HPA. From these, 4 sibships (5 patients) were affected by deficiency of 6-pyruvoyltetrahydropterin synthase. All of them were ethnically mixed, with some European ancestry detected in all. The age of diagnosis ranged from 2 to 9 years, and all were initially referred for investigation by having mental retardation and seizures. All of them showed low urinary biopterin levels and a marked elevation of neopterin. Although we detected only a few cases of HPA (30), 5 cases of 6-pyruvoyltetrahydropterin account for almost 20% of this total. The literature, however, reports a proportion of around 0.5%. As the frequency of classical phenylketonuria in our region is similar to that found in Caucasians (1/12,500), we believe that the frequency of this disease in South Brazil may be higher than expected (of the order of 1/400,000). We speculate that this finding could be related to a genetic drift (or founder effect).
Jardim
L B
LB
Medical Genetics Unit, Hospital de Clinicas de Porto Alegre, Brazil.
Giugliani
R
R
Coelho
J C
JC
Dutra-Filho
C S
CS
Blau
N
N
D000592:Amino Acid Metabolism, Inborn Errors / Q000201:enzymology / Q000453:epidemiology*; D001708:Biopterins / Q000031:analogs & derivatives* / Q000172:deficiency / Q000652:urine; D001938:Brazil / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D006801:Humans; D019798:Neopterin; D010649:Phenylalanine / Q000378:metabolism; D044465:White People
D001708:Biopterins; D010649:Phenylalanine; D019798:Neopterin; C003402:sapropterin