Pattern of Cbl, MMA, and HCys values in patients with clinical responses to Cbl therapy. Serum, Cbl, and MMA were measured on at least one occasion in 35 of the 37 patients with clinical responses to Cbl therapy, and serum HCys was also measured in 34 of these patients. The values shown represent the lowest pretherapy serum Cbl value and the highest pretherapy serum metabolite values obtained for each patient. Serum Cbl levels were defined as low (<201 pg/mL), intermediate (201 to 300 pg/mL), or normal (above 300 pg/mL). Normal metabolite levels were <251 nmol/L for MMA and <12.2 μmol/L for HCys. *MMA values in both of these cases were reported as below 400 nmol/L. Cbl indicates cobalamin; MMA, methylmalonic acid; HCys, homocysteine.