Background: Familial central diabetes insipidus (DI), usually an autosomal dominant disorder, is caused by mutations in arginine vasopressinneurophysin II (AVP-NPII) gene that leads to aberrant preprohormone processing and gradual destruction of AVP-secreting cells.
Objective and hypotheses: To determine clinical and molecular characteristics of patients with familial central DI from two different families.
Method: The diagnosis of central DI was established by 24-h urine collection, water deprivation test, and desmopressin challenge. To confirm the diagnosis of familial central DI, the entire coding region of AVP-NPII gene was amplified and sequenced. A total of eight affected patients and three unaffected healthy relatives from two families were studied.
Results: Genetic analysis revealed a previously reported heterozygous mutation (p.C98X) in family A, and a heterozygous novel mutation (p.G45C) in family B, both detected in exon 2 of AVP-NPII gene. When we compared the clinical characteristics of the two families, we noticed that as the age of onset of symptoms in family A ranges between 4 and 7 years, it was <1 year in family B. Additionally, pituitary bright spot was present in the affected siblings, but absent in their affected parents.
Conclusion: Familial central DI is a progressive disease, and age of onset of symptoms can differ depending on the mutation. Bright spot on pituitary MRI might be present at onset, but become invisible over time. Genetic testing and appropriate counselling should be given in familial cases of central DI to ensure adequate treatment, and to avoid chronic water deprivation that might result in growth retardation in childhood.
Funding: This research was funded by the Scientific and Technological Research Council of Turkey (SBAG Project No: 112S513).
01 Oct 2015 - 03 Oct 2015