Iron and protein sufficiency and red cell indices in phenylketonuria.

OBJECTIVE AND METHODS: We reviewed records of 41 children with treated phenylketonuria (PKU) in order to evaluate hematopoiesis and the effect of iron and protein sufficiency.
RESULTS: Six children (15%) were found to have anemia. Combined depletion of iron and protein stores was most likely to result in anemia, and two of the three children with this finding were anemic. Four children (10%) had evidence of iron deficiency without anemia (a precursor stage of iron deficiency anemia). Clinically significant iron depletion was found in older as well as younger children (well beyond the traditional infant/toddler deficient years). Plasma albumin was normal in all children and was not adequately sensitive to detect protein depletion sufficient to cause anemia or decreased growth. However, low plasma prealbumin (a more sensitive marker of protein sufficiency) correlated significantly with altered hematopoiesis or poor growth.
CONCLUSION: Compared to non-affected individuals, children with treated PKU make fewer red cells that have normal volume but increased hemoglobin per cell, resulting in a lower calculated hematocrit when measured by electronic cell counting. In the presence of iron or protein depletion, anemia may result. Routine monitoring of ferritin, complete blood counts and prealbumin are recommended for children with PKU at all ages.