Familial neurohypophyseal diabetes insipidus (DI) is a rare genetic disorder caused by vasopressin deficiency due to AVP gene mutations. This case report describes the genetic findings and clinical profiles of three generations within a family affected by hereditary central DI and managed with desmopressin. An 8-month-old male infant was admitted due to persistent polyuria and polydipsia that had been present since birth. History revealed a daily fluid intake of 7,200 mL and required 13 full diapers. The water deprivation test revealed a serum osmolality >300 mOsm/kg with a concurrently low urine osmolality (<300 mOsm/kg), confirming the diagnosis of DI. Desmopressin therapy was initiated for the patient. Using next-generation sequencing, a heterozygous variant c.329G>A (p.Cys110Tyr) was detected in the AVP gene. Following our patient's diagnosis, we evaluated first cousin once removed (on the maternal side) for similar symptoms. Upon identification of the heterozygous AVP variant via next-generation sequencing, desmopressin treatment was started. The same variant was detected in our patient's grandfather, mother, aunt, great-uncle, and first cousin once removed. Polyuria and polydipsia were present in all patients included in our case series. The grandfather and great-uncle, who were initially diagnosed, experienced delayed diagnosis and later developed renal complications. In contrast, the following generations of the family were diagnosed early. In familial cases, parents are often familiar with the clinical features of DI, allowing them to ensure adequate hydration, manage polyuria, and minimize the risk of dehydration. However, early diagnosis reduces the risk of long-term complications and enables effective family screening, allowing identification of previously unrecognized mild cases.

Congenital nephrogenic diabetes insipidus (NDI) is a hereditary disease characterized by a reduced response to arginine vasopressin in the renal collecting duct. NDI is primarily caused by mutations in the arginine vasopressin receptor 2 (AVPR2). Several animal models have been developed for congenital NDI; however, the appropriate models are limited. Thus, we constructed a novel Avpr2-deficient rat model using gene-editing technology to study the pathophysiological mechanisms of NDI. Avpr2-deficient rats were generated via a novel genome editing approach termed the rat Genome-editing via Oviductal Nucleic Acid Delivery (rGONAD) method. The phenotypes were analyzed using biological, molecular, and histological examinations. The effects of hydrochlorothiazide (40 mg/kg/d) on 24-h water intake, urine volume, and urine osmolality were evaluated in a metabolic cage. Avpr2-deficient rats were born and weaned under normal rearing conditions and exhibited symptoms similar to those of human congenital NDI, such as polydipsia, polyuria, and growth retardation. Although they exhibited hydronephrosis-like kidneys, no glomerular or tubular damage was observed. Aquaporin-2 was retained in the cytoplasm of collecting duct cells, and its phosphorylation was suppressed. Administration of hydrochlorothiazide decreased urine volume and improved urine osmolality in Avpr2-deficient rats. Avpr2-deficient rats are a reliable model of congenital NDI for elucidating the underlying mechanisms and identifying therapeutic targets.

Hereditary central diabetes insipidus (CDI) is a genetic disorder characterized by polydipsia and polyuria. Most known mutations are located in the arginine-vasopressin (AVP) gene. Here, we describe a Swiss family with an autosomal dominant mutation in the AVP gene region encoding for the carrier protein neurophysin II (P55R). In addition, we discuss the algorithm for diagnosing and treating patients with hereditary CDI based on this Swiss family.

Central diabetes insipidus (CDI) occurs secondary to deficient synthesis or secretion of arginine vasopressin peptide from the hypothalamo-neurohypophyseal system (HNS). It is characterized by polydipsia and polyuria (urine output >30mL/kg/day in adults and >2l/m2/24h in children) of dilute urine (<250mOsm/L). It can result from any pathology affecting one or more components of the HNS including the hypothalamic osmoreceptors, supraoptic or paraventricular nuclei, and median eminence of the hypothalamus, infundibulum, stalk or the posterior pituitary gland. MRI is the imaging modality of choice for evaluation of the hypothalamic-pituitary axis (HPA), and a dedicated pituitary or sella protocol is essential. CT can provide complimentary diagnostic information and is also of value when MRI is contraindicated. The most common causes are benign or malignant neoplasia of the HPA (25%), surgery (20%), and head trauma (16%). No cause is identified in up to 30% of cases, classified as idiopathic CDI. Knowledge of the anatomy and physiology of the HNS is crucial when evaluating a patient with CDI. Establishing the etiology of CDI with MRI in combination with clinical and biochemical assessment facilitates appropriate targeted treatment. This chapter illustrates the wide variety of causes and imaging correlates of CDI on neuroimaging, discusses the optimal imaging protocols, and revises the detailed neuroanatomy required to interpret these studies.

This review focuses on the cellular and molecular aspects underlying familial neurohypophyseal diabetes insipidus (DI), a rare disorder that is usually transmitted in an autosomal-dominant fashion. The disease, manifesting in infancy or early childhood and gradually progressing in severity, is caused by fully penetrant heterozygous mutations in the gene encoding prepro-vasopressin-neurophysin II, the precursor of the antidiuretic hormone arginine vasopressin (AVP). Post mortem studies in affected adults have shown cell degeneration in vasopressinergic hypothalamic nuclei. Studies in cells expressing pathogenic mutants and knock-in rodent models have shown that the mutant precursors are folding incompetent and fail to exit the endoplasmic reticulum (ER), as occurs normally with proteins that have entered the regulated secretory pathway. A portion of these mutants is eliminated via ER-associated degradation (ERAD) by proteasomes after retrotranslocation to the cytosol. Another portion forms large disulfide-linked fibrillar aggregates within the ER, in which wild-type precursor is trapped. Aggregation capacity is independently conferred by two domains of the prohormone, namely the AVP moiety and the C-terminal glycopeptide (copeptin). The same domains are also required for packaging into dense-core secretory granules and regulated secretion, suggesting a disturbed balance between the physiological self-aggregation at the trans-Golgi network and avoiding premature aggregate formation at the ER in the disease. The critical role of ERAD in maintaining physiological water balance has been underscored by experiments in mice expressing wild-type AVP but lacking critical components of the ERAD machinery. These animals also develop DI and show amyloid-like aggregates in the ER lumen. Thus, the capacity of the ERAD is exceeded in autosomal dominant DI, which can be viewed as a neurodegenerative disorder associated with the formation of amyloid ER aggregates. While DI symptoms develop prior to detectable cell death in transgenic DI mice, the eventual loss of vasopressinergic neurons is accompanied by autophagy, but the mechanism leading to cell degeneration in autosomal dominant neurohypophyseal DI still remains unknown.