Biotin deficiency with neurologic and cutaneous manifestations but without organic aciduria

Abstract

bilirubin concentrations decreased markedly and for a longer duration. The free bilirubin procedure provided additional insight into bilirubin binding by yielding the maximum molar binding capacity and the dissociation constant of our patient's serum. Despite high total bilirubin concentrations, Scatchard plots obtained by titrating bilirubin into our patient 's serum were apparently linear within the range of concentrations used (10 to 20 mg/d l above plasma values). The apparent decrease in the maximum molar binding capacity and the decrease in the dissociation constant are indications of the relatively smaller number of bilirubin binding sites needed and the increased affinity of overall binding after plasmapheresis (Table). These two changes produced the markedly lower free bilirubin at essentially the same total bilirubin concentration seen after the procedure. The rise in free bilirubin concentrations in our patient may have resulted from a concurrent small increase in total bilirubin concentration and fall in albumin concentration secondary to severe injury, with its complications and treatment. We believe that the free bilirubin determinations more adequately assessed the bilirubin-albumin equilibrium and reflected the effects of plasmapheresis more accurately than would measurements of total bilirubin. This case does not establish a critical concentration of free bilirubin that is dangerous to such a patient. Furthermore, it does not imply that the free bilirubin concentration would have a similar relation to the bilirubin-albumin ratio in a newborn infant or a patient with hyperbilirubinemia of a different cause. It does demonstrate a successful method of monitoring and lowering free bilirubin in Crigler-Najjar syndrome.