Possible high frequency of tetrahydrobiopterin deficiency in south Brazil.

[classical phenylketonuria]

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 ).

Diseases
Validation

Diseases presenting "common form" symptom

achondroplasia

alexander disease

benign recurrent intrahepatic cholestasis

cadasil

child syndrome

classical phenylketonuria

cutaneous mastocytosis

erythropoietic protoporphyria

familial mediterranean fever

hereditary cerebral hemorrhage with amyloidosis

hodgkin lymphoma, classical

holt-oram syndrome

homocystinuria without methylmalonic aciduria

oral submucous fibrosis

pendred syndrome

primary hyperoxaluria type 1

severe combined immunodeficiency

thoracic outlet syndrome

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