ESPE Abstracts

Background: Nephrogenic diabetes insipidus (NDI) is caused by inability of renal collecting duct cells to respond to arginine vassopresin (AVP)/antidiurethic hormone (ADH).

Objective and hypotheses: The majority of patients (about 90%) have type 1, X-linked recessive form, of NDI caused by mutation in gene encoding the vassopresin V2 receptor. Type 2, autosomal NDI, have the rest 10% of patients. This type is caused by the aquaporin-2 water channel (AQP2) gene mutations.

Method: We present a 7-year-old boy with a history of excretion of a large amount of dilute urine, thirst, and polydypsia since infancy. The boy had several vomiting episodes with mild dehydration during the first 3 years of life. No evidence of headaches, dizziness, or visual problems. He drinks between 2 and 3 l/day and has 24 h diuresis of 2 l. He has normal prepubertal appearance with appropriate weight (+0.85 SDS) and height (+0.15 SDS) for his age. Boy’s intelligence is normal, too. Diagnostic assessment was achieved according to clinical findings, kidney ultrasound, a water deprivation test and molecular analysis.

Results: Kidney ultrasound was uneventful. Water deprivation test showed urine osmolality 26 mOsm/kg after 8 h of dehydration. After desmopressin administration urine osmolality was 22.1 mOsm/kg. Serum osmolality was in normal range for the sex and age before and after desmopressin administration. This implicates nephrogenic form of diabetes insipidus. Molecular analyses showed a hemizygous c.317G>A mutation in exon 2 of AVPR2 (p.Arg(CGT)106His(CAT)), which was inherited from his mother. The treatment includes high liquids and low salt intake in addition to hydrochlortiazide.

Conclusions: This patient is the first case with confirmed X-linked recessive form of NDI in Macedonia. Molecular analysis confirmed the clinical diagnosis and enabled genetic advice in this family.