Dihydropyrimidine dehydrogenase (DPD) deficiency is an autosomal recessive disease characterised by thymine-uraciluria in homozygous deficient patients and has been associated with a variable clinical phenotype. In order to understand the genetic and phenotypic basis for DPD deficiency, we have reviewed 17 families presenting 22 patients with complete deficiency of DPD. In this group of patients, 7 different mutations have been identified, including 2 deletions [295-298delTCAT, 1897delC], 1 splice-site mutation [IVS14+1G>A)] and 4 missense mutations (85T>C, 703C>T, 2658G>A, 2983G>T). Analysis of the prevalence of the various mutations among DPD patients has shown that the G-->A point mutation in the invariant splice donor site is by far the most common (52%), whereas the other six mutations are less frequently observed. A large phenotypic variability has been observed, with convulsive disorders, motor retardation and mental retardation being the most abundant manifestations. A clear correlation between the genotype and phenotype has not been established. An altered beta-alanine, uracil and thymine homeostasis might underlie the various clinical abnormalities encountered in patients with DPD deficiency.
A prospective study was carried out to identify predictors of independent walking in 31 children with either spastic diplegia or triplegia, observed from the age of 9 to 18 months (mean, 11 months) and followed for a mean period of 30 months (range, 24 to 36 months). Mean age at most recent examination was 41 months (range, 36 to 54 months). We used an 18-item scheme to chart the acquisition, from the prone position, of prelocomotor, sitting, and locomotor skills. Examinations were conducted every 6 months and videotaped according to a standardized procedure. At latest assessment 18 (58%) of the 31 children had achieved walking, 7 (23%) independently and 11 (35%) with assistance; 13 (42%) did not achieve walking. Ambulatory status was related to developmental quotient and visual acuity: all the children who became independent walkers had normal visual acuity and in 86% of cases a normal general development quotient. Moreover, we found a significant correlation between the number of gross motor skills achieved and the rate of achievement before 2 years of age and ambulatory status at 3 to 5 years of age. Ability to put weight on the hands while prone and to roll from supine to prone position by 18 months of age were significantly related to independent walking, while ability to sit without support was predictive only at around 24 months of age.
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