Multiple plasma exchanges successfully maintain a young adult patient with Crigler-Najjar syndrome type I

Circulating bilirubin and defense against kidney disease and cardiovascular mortality: mechanisms contributing to protection in clinical investigations

Unconjugated bilirubin is an endogenous circulating antioxidant, bound to albumin, and therefore is retained in the vascular compartment. Bilirubin has well-documented neurotoxic effects in infants; however, current evidence indicates mildly elevated bilirubin is associated with protection from cardiovascular disease and all-cause mortality in adults. Recent clinical studies show mildly elevated bilirubin is associated with protection from kidney damage and dysfunction, in addition to cardiovascular events and all-cause mortality in patients undergoing hemodialysis. This is the first review to examine the clinical evidence and summarize the potential mechanisms of action that link bilirubin to protection from kidney damage, subsequent kidney failure, and dialysis-related mortality. With this understanding, it is hoped that new therapies will be developed to prevent renal dysfunction and mortality from cardiovascular disease in at-risk individuals.

Bilirubin and beyond: a review of lipid status in Gilbert's syndrome and its relevance to cardiovascular disease protection

Gilbert's syndrome (GS) is characterized by a benign, mildly elevated bilirubin concentration in the blood. Recent reports show clear protection from cardiovascular disease in this population. Protection of lipids, proteins and other macromolecules from oxidation by bilirubin represents the most commonly accepted mechanism contributing to protection in this group. However, a recent meta-analysis estimated that bilirubin only accounts for ~34% of the cardioprotective effects within analysed studies. To reveal the additional contributing variables we have explored circulating cholesterol and triacylglycerol concentrations, which appear to be decreased in hyperbilirubinemic individuals/animals, and are accompanied by lower body mass index in highly powered studies. These results suggest that bilirubin could be responsible for the development of a lean and hypolipidemic state in GS. Here we also discuss the possible contributing mechanisms that might reduce circulating cholesterol and triacylglycerol concentrations in individuals with syndromes affecting bilirubin metabolism/excretion, which we hope will stimulate future research in the area. In summary, this article is the first review of lipid status in animal and human studies of hyperbilirubinemia and explores possible mechanisms that could contribute to lowering circulating lipid parameters and further explain cardiovascular protection in Gilbert's syndrome.

Crigler-Najjar syndrome: therapeutic options and consequences of mutations in the UGT1A1 complex

Crigler-Najjar syndrome (CN), a rare inherited disorder characterized by failure of bilirubin glucuronidation, can lead to severe disability and death from kernicterus. Gilbert syndrome is a more common, benign familial unconjugated hyperbilirubinemia. The underlying problem in both conditions is impaired bilirubin conjugation and elimination due to a mutation in uridine 5'-diphosphate glucuronyltransferase. The mainstay of current management of CN is phototherapy, followed by liver transplantation. Here, we review other therapies, including hepatocyte transplantation, that have been successfully used to lessen the phenotype, although long-term engraftment of cells remains elusive. Gene therapy holds hope for the future whereby the patient's hepatocytes are transduced with the wild-type gene. Outstanding issues include safety of the gene vector and establishing immunotolerance to both vector and the new protein. The significant advances in understanding the relevance of mutations in UGT not only in glucuronidation of bilirubin, but other drugs and substances, are also reviewed.

Neurologic perspectives of Crigler-Najjar syndrome type I

Limited information exists on the neurologic sequelae of Crigler-Najjar syndrome type I despite this being the major morbidity of this rare autosomal recessive disorder of bilirubin conjugation that results in chronic unconjugated hyperbilirubinemia. Two patients with identical underlying genetic mutations resulting in Crigler-Najjar syndrome type I were assessed from a neurodevelopmental perspective in late childhood using age appropriate standardized measures. In addition, the English language literature of case reports and series describing the outcomes of patients with this disorder was reviewed (descriptive meta-analysis) and summarized with particular reference to neurologic symptomatology, pattern of neurologic disability, age of onset of symptoms, and therapeutic interventions. Despite radically different therapeutic interventions, our two patients did not differ in outcome measures. Review of the literature reveals distinct, often age-related, patterns of neurologic sequelae reflecting injury to basal ganglia, cerebellar, and likely hippocampal structures. Definitive prevention of the neurologic sequelae that often occur within the context of Crigler-Najjar syndrome type I requires that curative treatment (hepatic transplantation, presently, and gene therapy in the future) be applied prior to the possible onset of neurologic symptoms in adolescence.

Treatment of neonatal hyperbilirubinaemia by plasmapheresis

A term baby developed severe hyperbilirubinaemia in association with group-B streptococcal sepsis. Haemodynamic instability deterred us from performing exchange transfusion, and so plasmapheresis was used to lower the bilirubin level. The procedure was very effective and well tolerated.