Sarah Lawrence

Specific combination of compound heterozygous mutations in 17β-hydroxysteroid dehydrogenase type 4 (HSD17B4) defines a new subtype of D-bifunctional protein deficiency

BackgroundD-bifunctional protein (DBP) deficiency is typically apparent within the first month of life with most infants demonstrating hypotonia, psychomotor delay and seizures. Few children survive beyond two years of age. Among patients with prolonged survival all demonstrate severe gross motor delay, absent language development, and severe hearing and visual impairment. DBP contains three catalytically active domains; an N-terminal dehydrogenase, a central hydratase and a C-terminal sterol carrier protein-2-like domain. Three subtypes of the disease are identified based upon the domain affected; DBP type I results from a combined deficiency of dehydrogenase and hydratase activity; DBP type II from isolated hydratase deficiency and DBP type III from isolated dehydrogenase deficiency. Here we report two brothers (16½ and 14 years old) with DBP deficiency characterized by normal early childhood followed by sensorineural hearing loss, progressive cerebellar and sensory ataxia and subclinical retinitis pigmentosa.Methods and resultsBiochemical analysis revealed normal levels of plasma VLCFA, phytanic acid and pristanic acid, and normal bile acids in urine; based on these results no diagnosis was made. Exome analysis was performed using the Agilent SureSelect 50Mb All Exon Kit and the Illumina HiSeq 2000 next-generation-sequencing (NGS) platform. Compound heterozygous mutations were identified by exome sequencing and confirmed by Sanger sequencing within the dehydrogenase domain (c.101C>T; p.Ala34Val) and hydratase domain (c.1547T>C; p.Ile516Thr) of the 17β-hydroxysteroid dehydrogenase type 4 gene (HSD17B4). These mutations have been previously reported in patients with severe-forms of DBP deficiency, however each mutation was reported in combination with another mutation affecting the same domain. Subsequent studies in fibroblasts revealed normal VLCFA levels, normal C26:0 but reduced pristanic acid beta-oxidation activity. Both DBP hydratase and dehydrogenase activity were markedly decreased but detectable.ConclusionsWe propose that the DBP phenotype seen in this family represents a distinct and novel subtype of DBP deficiency, which we have termed type IV based on the presence of a missense mutation in each of the domains of DBP resulting in markedly reduced but detectable hydratase and dehydrogenase activity of DBP. Given that the biochemical testing in plasma was normal in these patients, this is likely an underdiagnosed form of DBP deficiency.

Growth hormone treatment of Canadian children: results from the GeNeSIS phase IV prospective observational study

BACKGROUND Country-specific data on outcomes of treatment with recombinant human growth hormone are lacking. We present such data for children treated with growth hormone in Canada. METHODS We describe characteristics and outcomes of 850 children (mean age at baseline 8.5 yr) treated with growth hormone constituting the Canadian cohort of the multinational phase IV prospective observational Genetics and Neuroendocrinology of Short-stature International Study (GeNeSIS). The diagnosis associated with short stature was as determined by the investigator. Auxological data were evaluated yearly until near-adult height. Adverse events were assessed in all growth-hormone-treated patients. RESULTS The diagnosis ascribed as the cause of short stature was growth hormone deficiency in 526 children (61.9%), predominantly organic rather than idiopathic, particularly congenital pituitary abnormalities and intracranial tumours. All diagnostic groups with sufficient patients for analysis had increased height velocity standard deviation score (SDS) and height SDS during growth hormone treatment. For patients who reached near-adult height (n = 293), the mean height SDS was within the normal range for about 80% of patients with organic growth hormone deficiency (n = 131) or idiopathic growth hormone deficiency (n = 50), 50% of patients with idiopathic short stature (n = 10) and 46% of patients with Turner syndrome (n = 79). Eleven deaths were reported, 7 in patients with organic growth hormone deficiency. Serious adverse events considered related to growth hormone treatment (n = 19) were isolated except for medulloblastoma recurrence (n = 2) and adenoidal hypertrophy (n = 2). INTERPRETATION Growth hormone treatment was effective and had a good safety profile in Canadian children. Growth hormone dosages were lower than in the US and global GeNeSIS cohorts, and a greater proportion of treated Canadian children had organic growth hormone deficiency. STUDY REGISTRATION ClinicalTrials.gov, no. NCT01088412.