Diseases

Long QT syndrome type 1

The long QT syndrome (LQTS) is a rare congenital heart condition with delayed repolarization following depolarization (excitation) of the heart, associated with syncope (fainting) due to ventricular arrhythmias, possibly of type torsade de pointes, which can deteriorate into ventricular fibrillation and ultimately sudden death. Arrhythmia in individuals with LQTS are often associated with exercise or excitement. Individuals with LQTS have a prolongation of the QT interval on the ECG. The Q wave on the ECG corresponds to ventricular depolarization while the T wave corresponds to ventricular repolarization. The QT interval is measured from the Q point to the end of the T wave. While many individuals with LQTS have persistent prolongation of the QT interval, some individuals do not always show the QT prolongation; in these individuals, the QT interval may prolong with the administration of certain medications.

Long QT syndrome type 2

The LQT2 type is the second most common gene location that is affected in long QT syndrome, making up about 25 to 30 percent of all cases. This form of long QT syndrome most likely involves mutations of the human ether-a-go-go related gene (HERG) on chromosome 7. The HERG gene (also known as KCNH2) is part of the rapid component of the potassium rectifying current (IKr). (The IKr current is mainly responsible for the termination of the cardiac action potential, and therefore the length of the QT interval.) The normally functioning HERG gene allows protection against early after depolarizations (EADs). Most drugs that cause long QT syndrome do so by blocking the IKr current via the HERG gene. These include erythromycin, terfenadine, and ketoconazole. The HERG channel is very sensitive to unintended drug binding due to two aromatic amino acids, the tyrosine at position 652 and the phenylalanine at position 656. These amino acid residues are poised so a drug binding to them will block the channel from conducting current. Other potassium channels do not have these residues in these positions and are therefore not as prone to blockage.

Long QT syndrome type 3

The LQT3 type of long QT syndrome involves mutation of the gene that encodes the alpha subunit of the Na+ ion channel. This gene is located on chromosome 3p21-24, and is known as SCN5A (also hH1 and NaV1.5). The mutations involved in LQT3 slow the inactivation of the Na+ channel, resulting in prolongation of the Na+ influx during depolarization. Paradoxically, the mutant sodium channels inactivate more quickly, and may open repetitively during the action potential. A large number of mutations have been characterized as leading to or predisposing LQT3. Calcium has been suggested as a regulator of SCN5A, and the effects of calcium on SCN5A may begin to explain the mechanism by which some these mutations cause LQT3. Furthermore mutations in SCN5A can cause Brugada syndrome, Cardiac Conduction disease and dilated cardiomyopathy. Rarely some affected individuals can have combinations of these diseases.

Loose anagen hair syndrome

Loose anagen hair syndrome (loose anagen syndrome, loose anagen hair) is a non-inflammatory, non-scarring form of hair loss. It is a condition that has been defined very recently and it generally affects the children. As the name suggests, loose anagen syndrome means growth of hair that is “loose” and easily pulled out of the hair follicle.

Lopes Gorlin syndrome

Lopes Gorlin syndrome is listed as a "rare disease" by the Office of Rare Diseases (ORD) of the National Institutes of Health (NIH). This means that Lopes Gorlin syndrome, or a subtype of Lopes Gorlin syndrome, affects less than 200,000 people in the US population.

Lopes Marques de Faria syndrome

A very rare syndrome characterized mainly by decreased hair and mental retardation. More detailed information about the symptoms, causes, and treatments of Lopes-Marques de Faria syndrome is available below.

Lopez Hernandez syndrome

Gomez and Lopez-Hernandez syndrome: A rare genetic condition characterized by various abnormalities such as mental deficiency, small head, short stature, eye problems and movement problems. More detailed information about the symptoms, causes, and treatments of Gomez and Lopez-Hernandez syndrome is available below.

Lou Gehrig’s disease

See "Amyotrophic lateral sclerosis" (Lou Gehrig's disease is a synonym for Amyotrophic lateral sclerosis)

Low-Grade Serous Ovarian Cancer

Compared with high-grade serous carcinoma, low-grade serous carcinoma of the ovary or peritoneum is a less frequent epithelial ovarian cancer type that is poorly sensitive to chemotherapy and affects younger women, many of whom endure years of ineffective treatments and poor quality of life.

Lowe Kohn Cohen syndrome

A very rare syndrome characterized by kidney disease, deafness and malformations of the anus and rectum.

Lowe oculocerebrorenal syndrome

Lowe oculocerebrorenal syndrome: A rare inherited metabolic disorder characterized primarily by eye and bone abnormalities, mental retardation and kidney problems.

Lower mesodermal defects

A very rare syndrome characterized mainly by defects of the lower trunk area such as the pelvic organs.

Lowry Maclean syndrome

A very rare syndrome characterized mainly by mental retardation, retarded growth, glaucoma, congenital heart defects and premature fusion of skull bones.

Lowry syndrome

A rare genetic disorder characterized by down slanting space between eyelids, bulbous nose, soft hands and tapering fingers.

Lowry Wood syndrome

A rare syndrome characterized by a small head, rapid involuntary eye movements (nystagmus) and abnormal development of the ends of long bones where growth occurs.

Lowry Yong syndrome

A rare syndrome characterized by a small head, rapid involuntary eye movements (nystagmus) and abnormal development of the ends of long bones where growth occurs.

Lubani Al Saleh Teebi syndrome

A rare syndrome characterized mainly by cystic fibrosis, metaloblastic anemia, mental retardation and gastritis due to helicobacter pylori.

Lubinsky syndrome

A very rare syndrome characterized mainly by a short head, deafness, cataracts and mental retardation.

Lucey Driscoll syndrome

A rare condition characterized by severe jaundice at birth and caused by the presence of a gestational hormone that passes from the mother to the infant across the placenta but eventually disappears after birth. Excessive jaundice result in kernicterus can cause complications such as brain damage.

Lucky Gelehrter syndrome

A very rare syndrome characterized mainly by mental retardation, short fingers, reduced muscle tone and spider veins (telangiectasia).

Lúes Congénita

Lues, congenital (medical condition): Syphilis inherited from mother during pregnancy.

Lujan Fryns syndrome

A rare genetic disorder characterized by mental retardation and marfanoid habitus (features of Marfan's syndrome)

Lumbar malsegmentation short stature

A very rare syndrome characterized mainly by short stature and abnormal segmentation of the vertebrae in the abdominal segment of the spine .

Lundberg syndrome

A rare syndrome involving cataracts, reduced hormone production by ovaries or testes and myopathy which mainly involves the facial and muscles close to the trunk.

Lung agenesis

A very rare syndrome characterized mainly by the failure of the lungs to develop fully, heart defects and thumb abnormalities.

Lung herniation congenital defect of sternem

A rare congenital disorder where a some of the lung tissues pushes through and opening in the breast bone. The mid-chest mass may change in size with inhalation and exhalation.

Lupus nephritis

Lupus nephritis is a rare kidney disorder that is a complication of systemic lupus erythematous (SLE), commonly known as lupus. The symptoms of lupus nephritis include blood in the urine, a foamy appearance to the urine, high blood pressure, and swelling in any part of the body. This condition typically occurs in people aged 20 to 40 years. Treatment may involve medications to suppress the immune system, dialysis, or a kidney transplant.