Bartter syndrome type 4

The following summary is from Orphanet, a European reference portal for information on rare diseases and orphan drugs.

Orpha Number: 89938

Definition

Infantile Bartter syndrome with deafness, a phenotypic variant of Bartter syndrome (see this term) is characterized by maternal polyhydramnios, premature delivery, polyuria and sensorineural deafness and is associated with hypokalemic alkalosis, increased levels of plasma renin and aldosterone, low blood pressure, and vascular resistance to angiotensin II.

Epidemiology

It is the least common of all recessive types of Bartter syndrome.

Clinical description

Infantile Bartter syndrome with deafness is a severe type of Bartter syndrome manifesting prenatally with maternal polyhydramnios (due to fetal polyuria) usually evident by the end of 2nd trimester, often leading to preterm labour and prematurity. Postnatally patients present with polyuria, isosthenuria/hyposthenuria and are at high risk of dehydration, hypovolemic hypotension and shock. Patients are found to have complete sensorineural deafness. Recurrent vomiting, muscle cramps, spasms and failure to thrive are observed. Progression to renal failure is frequent. Hypokalemic alkalosis, hypomagnesemia, hyperprostaglandin E-uria and hypochloremia are noted (hypercalciuria is only transient).

Etiology

Infantile Bartter syndrome with deafness is caused by a defect in chloride transport in thick ascending loop of Henle and distal convoluted tubule as a consequence of inactivating mutations of the gene BSND (1p32.3) encoding for the protein Barttin (Bartter syndrome type 4A), required for the location and proper function of the voltage sensitive, Ka and Kb chloride channels of the basolateral membrane, (ClCKa and ClCKb). In addition to mutations of Barttin, infantile Bartter syndrome with deafness may be caused by digeneic ( CLCKA and CLCKB 1p36) mutations inactivating all the 4 alleles of the 2 genes (or Bartter syndrome type 4B). CLCKa is highly expressed in the inner ear and contributes to maintain the high potassium ion concentration in the endolymph necessary for normal hearing, disruption of the function of which thus leads to nerve deafness.

Genetic counseling

The disease is transmitted in an autosomal recessive manner.

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