Glycerol kinase deficiency and adrenal hypoplasia congenita

Identification of novel mutations of the DAX-1 gene in patients with X-linked adrenal hypoplasia congenita

OBJECTIVE

X-linked adrenal hypoplasia congenita (AHC) is a condition clinically featuring adrenal insufficiency and hypogonadotropic hypogonadism caused by mutations of DAX-1. This study was undertaken to characterize the molecular defects of DAX-1 in 3 unrelated Korean patients with AHC.

PATIENTS AND METHODS

Patient 1 is a 6-year-old boy who presented with a salt-losing adrenal crisis in the neonatal period. Patient 2 is a 3-year-old boy who manifested aspiration pneumonia and adrenal insufficiency at the age of 1 month. Patient 3 is a 7-year-old boy who developed an adrenal crisis at the age of 3 days. In each of these patients, DAX-1 was analyzed by direct DNA sequencing after polymerase chain reaction amplification of the entire coding region.

RESULTS

Direct sequencing of DAX-1 revealed two novel mutations, 1156_1157delCT in patient 1 and another novel nonsense mutation W105X in patient 2. Patient 3 had complete deletion of DAX-1. In patient 3, serum transaminases and creatine kinase levels were elevated while the glycerol kinase activity of leukocytes was decreased. Markedly elevated glycerol excretion was detected by urine organic acid analysis. Patient 3 was diagnosed as Xp21 contiguous gene syndrome associated with deletions of the entire IL1RAPL, GK genes and the C-terminal region of DMD gene.

CONCLUSIONS

Two novel mutations of DAX-1 were detected in 2 unrelated patients with AHC, and complete deletion of DAX-1 in a patient with Xp21 contiguous gene syndrome who also presented with glycerol kinase deficiency, Duchenne muscular dystrophy, and AHC.

Isolated and contiguous glycerol kinase gene disorders: a review

Glycerol kinase deficiency (GKD) is an X-linked recessive disorder. There are two types. an isolated form and a complex form. We review the clinical, biochemical and molecular genetic features of GKD. The clinical and biochemical phenotype of isolated GKD may vary from a life-threatening childhood metabolic crisis to asymptomatic adult 'pseudohypertriglyceridaemia', resulting from hyperglycerolaemia. To date 38 patients from 24 families with isolated GKD have been reported. At least 7 of these patients had a metabolic crisis during a catabolic condition. The complex GKD is an Xp21 contiguous gene syndrome involving the glycerol kinase locus together with the adrenal hypoplasia congenita (AHC) or Duchenne muscular dystrophy (DMD) loci or both. Clinical features of a patient with complex GKD depend on the loci that are involved. Approximately 100 patients from 78 families with a complex GKD have been reported. Seventeen patients with complex GKD (AHC-GKD-DMD or AHC-GKD) died in the neonatal period or early childhood because of unrecognized or inappropriate management of adrenal dysfunction. Since the outcome of the crisis in GKD is highly dependent on the physicians' knowledge of the disease, we devised an algorithmic approach to the diagnosis. From molecular genetic investigations of isolated GKD, 7 missense mutations, 2 splice site mutations, I nonsense mutation, 1 Alu Sx insertion and 2 small deletions were reported for isolated GKD in 13 unrelated families. In 4 families consisting of more than one patient with the same biochemical and genetic defect, the phenotypic variability of the isolated GKD was remarkable. The clinical variability in isolated GKD cannot be explained by biochemical or by molecular heterogeneity. Isolated GKD patients showed a tendency towards hypoglycaemia with hyperketonaemia; whether the clinical symptoms of GKD are caused by dysfunction of gluconeogenesis and/or ketolysis needs to be investigated further.