Lymphoblasts and diagnosis of pyruvate carboxylase deficiency

Pyruvate carboxylase activity was measured in phytohemagglutinin-transformed lymphocytes (i.e. lymphoblasts). Mean value +/- S.D. for 10 controls was 259 +/- 38 pmoles/min per mg protein. It was about 7 times higher than that of peripheral leukocytes and a half of cultured skin fibroblasts with similar techniques. Deficient pyruvate carboxylase activity less than 6 pmoles/min per mg protein was demonstrated in the lymphoblasts from a patient with biotin-dependent multiple carboxylase deficiency. It is suggested that lymphoblasts may allow more reliable and ready diagnosis of patients with pyruvate carboxylase deficiency.