Effect of nitisinone (NTBC) treatment on the clinical course of hepatorenal tyrosinemia in Québec.

BACKGROUND: Hepatorenal tyrosinemia (HT1, fumarylacetoacetate hydrolase deficiency, MIM 276700) can cause severe hepatic, renal and peripheral nerve damage. In Québec, HT1 is frequent and neonatal HT1 screening is practiced. Nitisinone (NTBC, Orfadin ®) inhibits tyrosine degradation prior to the formation of toxic metabolites like succinylacetone and has been offered to HT1 patients in Québec since 1994. METHODS: We recorded the clinical course of 78 Québec HT1 patients born between 1984 and 2004. There were three groups: those who never received nitisinone (28 patients), those who were first treated after 1 month of age (26 patients) and those treated before 1 month (24 patients). Retrospective chart review was performed for events before 1994, when nitisinone treatment began, and prospective data collection thereafter. FINDINGS: No hospitalizations for acute complications of HT1 occurred during 5731 months of nitisinone treatment, versus 184 during 1312 months without treatment (p<0.001). Liver transplantation was performed in 20 non-nitisinone-treated patients (71%) at a median age of 26 months, versus 7 late-treated patients (26%, p<0.001), and no early-treated patient (p<0.001). No early-treated patient has developed detectable liver disease after more than 5 years. Ten deaths occurred in non-nitisinone treated patients versus two in treated patients (p<0.01). Both of the latter deaths were from complications of transplantation unrelated to HT1. One probable nitisinone-related event occurred, transient corneal crystals with photophobia. INTERPRETATION: Nitisinone treatment abolishes the acute complications of HT1. Some patients with established liver disease before nitisinone treatment eventually require hepatic transplantation. Patients who receive nitisinone treatment before 1 month had no detectable liver disease after more than 5 years.

Clinical heterogeneity and molecular findings in five Polish patients with glycerol kinase deficiency: investigation of two splice site mutations with computerized splice junction analysis and Xp21 gene-specific mRNA analysis.

Five cases of glycerol kinase deficiency are presented with clinical, biochemical, and genetic results. Two had the glycerol kinase deficiency as part of an Xp21 contiguous gene deletion syndrome-complex form-and three had an isolated form of the enzyme deficiency. In these we found two splice site mutations (IVS1+4A>G, IVS9-1G>T) and one insertion (1393_1394insG). In patients with the complex form, a deletion of the DAX1, GK genes and the distal part of the DMD gene was found. A computerized study was performed to predict the effects of the splice site mutations. It showed that the IVS9-1G>T mutation substantially altered and removed the wild-type site and enhanced a cryptic site seven nucleotides downstream, and that the IVS1+4A>G diminished the strength of the wild-type donor site from strong to leaky. To verify these predictions, we developed an RT-PCR system with gene-specific primers that exclusively amplifies the Xp21 glycerol kinase gene transcript. Identification of individuals at risk is motivated by a need to avoid delay in a correct diagnosis. For reliable identification of heterozygotes for isolated glycerol kinase deficiency, knowledge of the specific mutation in the proband is required. This is easily obtained with the RT-PCR analyses developed in this study.

Glycerol metabolism and the determination of triglycerides--clinical, biochemical and molecular findings in six subjects.

Recent recommendations in the National Cholesterol Education Program Expert Panel on Detection, Evaluation and Treatment of High Blood Cholesterol in Adults (ATPIII) are expected to increase the number of triglyceride (TG) determinations and consequently the risk of misinterpretation of "non-blanked" results with co-determination of free glycerol. Glycerol-kinase deficiency (GKD) is one cause of falsely elevated TG results. The natural history of isolated GKD with symptom-free cases and cases with e.g. severe episodes of hypoglycemia and/or ketoacidosis challenges the laboratories to identify cases of GKD and family members at risk. "Blanked" methods reporting both glycerol and TG concentration are therefore desirable. Molecular studies of the glycerol kinase (GK) and DAX1 genes were performed on four cases of "persistent hypertriglyceridemia" found in an Italian population and on two pediatric cases with high serum glycerol concentration. Two new missense mutations were found (C358Y, T961). Molecular modeling on GK from E. coli, indicate that these mutations are located in parts of the enzyme important for enzyme formation or activity. One splice-site mutation, (IVS9A-1G>A), was found in two brothers. Splice-junction analysis indicates that it destroys the splice site and results in a mixture of mRNA. Deletion of the GK and DAX1 genes was found in one child with symptoms of adrenal failure. A female with glycerolemia and glyceroluria had normal GK activity but possibly slightly decreased ability to oxidize glycerol.