Jervell and Lange-Nielsen syndrome
Encyclopedia
Jervell and Lange-Nielsen syndrome, a type of long QT syndrome
, causes the cardiac muscle
to take longer than usual to recharge between beats. If untreated, the irregular heartbeats, called arrhythmias, can lead to fainting, seizure
s, or sudden death. The disorder also contributes to hearing loss.
This condition is an autosomal recessive disorder that affects an estimated 1.6 to 6 in 1 million children, and is responsible for less than 10 percent of all cases of long QT syndrome.
Mutation
s in the KCNE1
and KCNQ1 genes cause Jervell and Lange-Nielsen syndrome. The proteins produced by these two genes work together to form a potassium channel
that transports positively charged potassium
ion
s out of cells
. The movement of potassium ions through these channels is critical for maintaining the normal functions of the inner ear
and cardiac muscle.
About 90 percent of cases of Jervell and Lange-Nielsen syndrome are caused by mutations in the KCNQ1 gene. KCNE1 mutations are responsible for the remaining 10 percent of cases. Mutations in these genes alter the usual structure and function of potassium channels or prevent the assembly of normal channels. These changes disrupt the flow of potassium ions in the inner ear and in cardiac muscle, leading to the hearing loss and irregular heart rhythm characteristic of Jervell and Lange-Nielsen syndrome.
Beta-blocker + dual mode/dual chamber/dual sensing pacemaker if the patient is symptomatic or there is documented syncope.
Long QT syndrome
The long QT syndrome is a rare inborn heart condition in which delayed repolarization of the heart following a heartbeat increases the risk of episodes of torsade de pointes . These episodes may lead to palpitations, fainting and sudden death due to ventricular fibrillation...
, causes the cardiac muscle
Cardiac muscle
Cardiac muscle is a type of involuntary striated muscle found in the walls and histologic foundation of the heart, specifically the myocardium. Cardiac muscle is one of three major types of muscle, the others being skeletal and smooth muscle...
to take longer than usual to recharge between beats. If untreated, the irregular heartbeats, called arrhythmias, can lead to fainting, seizure
Seizure
An epileptic seizure, occasionally referred to as a fit, is defined as a transient symptom of "abnormal excessive or synchronous neuronal activity in the brain". The outward effect can be as dramatic as a wild thrashing movement or as mild as a brief loss of awareness...
s, or sudden death. The disorder also contributes to hearing loss.
Genetic prevalence
Mutation
Mutation
In molecular biology and genetics, mutations are changes in a genomic sequence: the DNA sequence of a cell's genome or the DNA or RNA sequence of a virus. They can be defined as sudden and spontaneous changes in the cell. Mutations are caused by radiation, viruses, transposons and mutagenic...
s in the KCNE1
KCNE1
Potassium voltage-gated channel subfamily E member 1 is a protein that in humans is encoded by the KCNE1 gene.KCNE1 is a gene associated with Long QT syndrome type 5. It can both cause Romano-Wards syndrome and Jervell Lange-Nielsens syndrome -External links:*...
and KCNQ1 genes cause Jervell and Lange-Nielsen syndrome. The proteins produced by these two genes work together to form a potassium channel
Potassium channel
In the field of cell biology, potassium channels are the most widely distributed type of ion channel and are found in virtually all living organisms. They form potassium-selective pores that span cell membranes...
that transports positively charged potassium
Potassium
Potassium is the chemical element with the symbol K and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Potassium and sodium are...
ion
Ion
An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge. The name was given by physicist Michael Faraday for the substances that allow a current to pass between electrodes in a...
s out of cells
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
. The movement of potassium ions through these channels is critical for maintaining the normal functions of the inner ear
Ear
The ear is the organ that detects sound. It not only receives sound, but also aids in balance and body position. The ear is part of the auditory system....
and cardiac muscle.
About 90 percent of cases of Jervell and Lange-Nielsen syndrome are caused by mutations in the KCNQ1 gene. KCNE1 mutations are responsible for the remaining 10 percent of cases. Mutations in these genes alter the usual structure and function of potassium channels or prevent the assembly of normal channels. These changes disrupt the flow of potassium ions in the inner ear and in cardiac muscle, leading to the hearing loss and irregular heart rhythm characteristic of Jervell and Lange-Nielsen syndrome.
Treatment
Beta-blocker like propranolol if the patients is asymptomatic or there is no documented syncope.Beta-blocker + dual mode/dual chamber/dual sensing pacemaker if the patient is symptomatic or there is documented syncope.