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.
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 1month of age (26 patients) and those treated before 1month (24 patients). Retrospective chart review was performed for events before 1994, when nitisinone treatment began, and prospective data collection thereafter.
No hospitalizations for acute complications of HT1 occurred during 5731months of nitisinone treatment, versus 184 during 1312months without treatment (p<0.001). Liver transplantation was performed in 20 non-nitisinone-treated patients (71%) at a median age of 26months, 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 5years. 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.
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 1month had no detectable liver disease after more than 5years.
"Newborn screening for HT1 is not widely available because of the rarity of HT1 in most areas. However together with early treatment with nitisinone and diet, it is the medical management of choice [11,12]. Recent studies have shown confirmed this  Newborn screening is best performed using succinylacetone (SA) as a primary marker because it is sensitive and specific. "
[Show abstract][Hide abstract] ABSTRACT: The management of tyrosinaemia type 1 (HT1, fumarylacetoacetase deficiency) has been revolutionised by the introduction of nitisinone but dietary treatment remains essential and the management is not easy. In this review detailed recommendations for the management are made based on expert opinion, published case reports and investigational studies as the evidence base is limited and there are no prospective controlled studies.
The added value of this paper is that it summarises in detail current clinical knowledge about HT1 and makes recommendations for the management.
[Show abstract][Hide abstract] ABSTRACT: Tyrosinaemia type 1 (HT1) is a rare disorder of tyrosine metabolism leading to liver failure and hepatocellular carcinoma. Treatment previously consisted of dietary restriction and orthotopic liver transplantation (OLT) but was transformed by the introduction of nitisinone in 1992. We describe the impact of nitisinone on the outcome and need for OLT in a single centre.
A retrospective analysis was performed of patients treated for HT1 at Birmingham Children's Hospital from 1989-2009.
Thirty eight patients were treated during the study period. Prior to 1992 6/7 (85.7 %) underwent OLT compared to 7/31 (22.6 %) after 1992 (p = 0.004) when nitisinone treatment was available. Furthermore, nitisinone-treated patients proceeding to OLT started treatment at a median age of 428 (86-821) days compared to 52 (2-990) days in those who did not (p = 0.004). Pre-OLT calculated glomerular filtration rate (cGFR) was similar in both groups but nitisinone prevented early decline after OLT (pre-nitisinone median 99.8 to 45.8 ml/min/1.73 m2, p = 0.02 versus nitisinone-treated group median 104.3 to 89.9 ml/min/1.73 m2, p = 0.5). Urinary protein:creatinine ratio (PCR) fell post-OLT to within the normal range for those treated with nitisinone but remained elevated in those not treated with nitisinone. Tubular reabsorption of phosphate (TRP) was normal or near normal in both groups pre-OLT and post-OLT. Hypertension was commoner and more severe in those not treated with nitisinone.
Nitisinone reduces the need for OLT particularly when started early. For those progressing to OLT the use of prior nitisinone therapy results in a preservation of their subsequent renal function.
[Show abstract][Hide abstract] ABSTRACT: Background
Hepatorenal tyrosinaemia (Tyr 1) is a rare inborn error of tyrosine metabolism. Without treatment, patients are at high risk of developing acute liver failure, renal dysfunction and in the long run hepatocellular carcinoma. The aim of our study was to collect cross-sectional data.Methods
Via questionnaires we collected retrospective data of 168 patients with Tyr 1 from 21 centres (Europe, Turkey and Israel) about diagnosis, treatment, monitoring and outcome. In a subsequent consensus workshop, we discussed data and clinical implications.ResultsEarly treatment by NTBC accompanied by diet is essential to prevent serious complications such as liver failure, hepatocellular carcinoma and renal disease. As patients may remain initially asymptomatic or develop uncharacteristic clinical symptoms in the first months of life newborn mass screening using succinylacetone (SA) as a screening parameter in dried blood is mandatory for early diagnosis. NTBC-treatment has to be combined with natural protein restriction supplemented with essential amino acids. NTBC dosage should be reduced to the minimal dose allowing metabolic control, once daily dosing may be an option in older children and adults in order to increase compliance. Metabolic control is judged by SA (below detection limit) in dried blood or urine, plasma tyrosine (<400 ¿M) and NTBC-levels in the therapeutic range (20¿40 ¿M). Side effects of NTBC are mild and often transient.Indications for liver transplantation are hepatocellular carcinoma or failure to respond to NTBC. Follow-up procedures should include liver and kidney function tests, tumor markers and imaging, ophthalmological examination, blood count, psychomotor and intelligence testing as well as therapeutic monitoring (SA, tyrosine, NTBC in blood).Conclusion
Based on the data from 21 centres treating 168 patients we were able to characterize current practice and clinical experience in Tyr 1. This information could form the basis for clinical practice recommendations, however further prospective data are required to underpin some of the recommendations.
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