The aim of this study was to assess the prevalence of nutritional deficiency of vitamin B12 in long-term treated patients with phenylketonuria (PKU) and hyperfenylalaninemia (HPA), together with parameters of vitamin B12 and metabolic control.
Methods In 51 patients aged 3–48 years (28 children, 23 adults) was examined levels of active vitamin B12 in serum, folate concentration in blood, plasma homocysteine and methylmalonic acid concentrations in urine.
Results We found a statistically significant difference between the levels of folate in the blood among patients with PKU and HPA (p = 0.046, Mann Whitney U test). This difference was also statistically significant for adults with HPA and PKU (p = 0.004, Mann Whitney U test). There was a statistically significant difference in the proportion of normal homocysteine concentrations in plasma in the overall evaluation of both groups (p = 0.023, chi -square test). This difference was also statistically significant in adults with HPA and PKU (p = 0.032, chi -square test). In the group of adults we detected a statistically significant difference in the concentrations of active vitamin B12 in the blood as in the evaluation of the concentration and the proportion of patients with normal levels (p = 0.031, Mann Whitney U test, p = 0.006, chi -square test).
Conclusions In the analysed group of patients we demonstrated that our patients are at risk of vitamin B12 nutritional deficiency and the risk increases with age.