Abstract

BackgroundAdvances in the diagnosis and treatment of urea cycle disorders (UCDs) have led to a higher survival rate. The purpose of this study is to describe the characteristics of patients with urea cycle disorders in Spain.MethodsObservational, cross-sectional and multicenter study. Clinical, biochemical and genetic data were collected from patients with UCDs, treated in the metabolic diseases centers in Spain between February 2012 and February 2013, covering the entire Spanish population. Heterozygous mothers of patients with OTC deficiency were only included if they were on treatment due to being symptomatic or having biochemistry abnormalities.Results104 patients from 98 families were included. Ornithine transcarbamylase deficiency was the most frequent condition (64.4%) (61.2% female) followed by type 1 citrullinemia (21.1%) and argininosuccinic aciduria (9.6%). Only 13 patients (12.5%) were diagnosed in a pre-symptomatic state. 63% of the cases presented with type intoxication encephalopathy. The median ammonia level at onset was 298 μmol/L (169-615). The genotype of 75 patients is known, with 18 new mutations having been described. During the data collection period four patients died, three of them in the early days of life. The median current age is 9.96 years (5.29-18), with 25 patients over 18 years of age. Anthropometric data, expressed as median and z-score for the Spanish population is shown. 52.5% of the cases present neurological sequelae, which have been linked to the type of disease, neonatal onset, hepatic failure at diagnosis and ammonia values at diagnosis. 93 patients are following a protein restrictive diet, 0.84 g/kg/day (0.67-1.10), 50 are receiving essential amino acid supplements, 0.25 g/kg/day (0.20-0.45), 58 arginine, 156 mg/kg/day (109-305) and 45 citrulline, 150 mg/kg/day (105-199). 65 patients are being treated with drugs: 4 with sodium benzoate, 50 with sodium phenylbutyrate, 10 with both drugs and 1 with carglumic acid.ConclusionsStudies like this make it possible to analyze the frequency, natural history and clinical practices in the area of rare diseases, with the purpose of knowing the needs of the patients and thus planning their care.

Highlights

  • Advances in the diagnosis and treatment of urea cycle disorders (UCDs) have led to a higher survival rate

  • The incidence of UCDs varies between 1:22.1791:53.717 newborns [3,4,5,6,7] it could be higher, considering that not all the cases are detected by expanded newborn screening (NBS) and many can be undiagnosed cases with a fatal outcome

  • We present the data of the first registry of patients with UCDs in Spain

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Summary

Introduction

Advances in the diagnosis and treatment of urea cycle disorders (UCDs) have led to a higher survival rate. Urea cycle disorders (UCDs) are caused by a deficiency of one of the six enzymes in this cycle. As the metabolic steps take place in two different cellular compartments, two transporters are necessary: the ornithine/citrulline antiporter ORNT1, deficiency of which causes hyperornithinemia-hyperammonemia-homocitrullinuria syndrome and the glutamate/aspartate antiporter CITRIN, deficiency of which gives rise to type 2 citrullinemia. All these deficiencies are inherited in an autosomal recessive manner, except for OTC deficiency which is inherited in an X-linked recessive manner. The incidence of UCDs varies between 1:22.1791:53.717 newborns [3,4,5,6,7] it could be higher, considering that not all the cases are detected by expanded newborn screening (NBS) and many can be undiagnosed cases with a fatal outcome

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