Diseases

Metachromatic leukodystrophy

Metachromatic leukodystrophy is an inherited disorder characterized by the accumulation of fats called sulfatides in cells. This accumulation especially affects cells in the nervous system that produce myelin, the substance that insulates and protects nerves. Nerve cells covered by myelin make up a tissue called white matter. Sulfatide accumulation in myelin-producing cells causes progressive destruction of white matter (leukodystrophy) throughout the nervous system, including in the brain and spinal cord (the central nervous system) and the nerves connecting the brain and spinal cord to muscles and sensory cells that detect sensations such as touch, pain, heat, and sound (the peripheral nervous system).

The types, which may overlap, include:

  • Infantile form, occurring between ages 6 months and 2 years
  • Juvenile form, occurring between ages 3 and 6 (early juvenile) or between ages 6 and 16 (late juvenile)
  • Adult form, occurring at age 17 or older

In people with metachromatic leukodystrophy, white matter damage causes progressive deterioration of intellectual functions and motor skills, such as the ability to walk. Affected individuals also develop loss of sensation in the extremities (peripheral neuropathy), incontinence, seizures, paralysis, an inability to speak, blindness, and hearing loss. Eventually they lose awareness of their surroundings and become unresponsive. While neurological problems are the primary feature of metachromatic leukodystrophy, effects of sulfatide accumulation on other organs and tissues have been reported, most often involving the gallbladder.

The most common form of metachromatic leukodystrophy, affecting about 50 to 60 percent of all individuals with this disorder, is called the late infantile form. This form of the disorder usually appears in the second year of life. Affected children lose any speech they have developed, become weak, and develop problems with walking (gait disturbance). As the disorder worsens, muscle tone generally first decreases, and then increases to the point of rigidity. Individuals with the late infantile form of metachromatic leukodystrophy typically do not survive past childhood.

In 20 to 30 percent of individuals with metachromatic leukodystrophy, onset occurs between the age of 4 and adolescence. In this juvenile form, the first signs of the disorder may be behavioral problems and increasing difficulty with schoolwork. Progression of the disorder is slower than in the late infantile form, and affected individuals may survive for about 20 years after diagnosis.

The adult form of metachromatic leukodystrophy affects approximately 15 to 20 percent of individuals with the disorder. In this form, the first symptoms appear during the teenage years or later. Often behavioral problems such as alcoholism, drug abuse, or difficulties at school or work are the first symptoms to appear. The affected individual may experience psychiatric symptoms such as delusions or hallucinations. People with the adult form of metachromatic leukodystrophy may survive for 20 to 30 years after diagnosis. During this time there may be some periods of relative stability and other periods of more rapid decline.

Metachromatic leukodystrophy gets its name from the way cells with an accumulation of sulfatides appear when viewed under a microscope. The sulfatides form granules that are described as metachromatic, which means they pick up color differently than surrounding cellular material when stained for examination.

Metagonimiasis

Metagonimiasis: Infection with a parasitic intestinal fluke called Metagonimus yokogawa. Infection usually occurs when eating undercooked or salted fish which are infected with the parasite. It is most common in the Far East, Siberia, Israel and Spain

Metaphyseal acroscyphodysplasia

Metaphyseal acroscyphodysplasia: A very rare syndrome characterized mainly by bone abnormalities mainly involving the legs, and fingers and the arms to a lesser extent.

Metaphyseal anadysplasia

Metaphyseal anadysplasia (medical condition): A very rare syndrome where abnormal bone development starts early in life and is fairly severe but after a few years, the bones return to almost normal. Adult height is nearly normal and bowed limbs usually straighte

Metaphyseal chondrodysplasia Schmid type

Metaphyseal chondrodysplasia, Schmid type (MCDS), is a very rare inherited disorder characterized by short stature with abnormally short arms and legs (short-limbed dwarfism) and bowed legs (genu varum). Other physical characteristics may include outward "flaring" of the bones of the lower rib cage, lumbar lordosis, pain in the legs, and/or hip deformities in which the thigh bone is angled toward the center of the body (coxa vara). Such abnormalities of the legs and hips typically result in an unusual "waddling" walk (gait). MCDS is transmitted as an autosomal dominant trait.

Metaphyseal chondrodysplasia- others

McKusick type metaphyseal chondrodysplasia: A rare genetic disorder characterized by short stature, skeletal abnormalities and fine, fragile hair.

Metaphyseal dysplasia maxillary hypoplasia brachydactyly

Metaphyseal dysplasia - maxillary hypoplasia - brachydactyly: A very rare syndrome characterized mainly by short fingers, underdeveloped upper jaw and bone abnormalities involving the cone-shaped portion near the end of the bones where growth occurs

Metaphyseal dysplasia Pyle type

Metaphyseal dysplasia is a very rare disorder in which the outer part of the shafts of long bones is unusually thin with a tendency to fracture. Aside from valgus knee deformities (commonly known as knock-knee), many patients with metaphyseal dysplasia exhibit few or no symptoms. However, the disorder comes in a variety of forms, some of which cause serious problems including mental retardation, blindness, and deafness.

Metastatic castration-resistant prostate cancer

Castration-resistant prostate cancer (CRPC) is a form of
advanced prostate cancer. With CRPC, the cancer no longer
completely responds to treatments that lower testosterone.
It shows signs of growth, like a rising PSA (prostate-specific
antigen), even with low levels of testosterone.
With Metastatic CRPC (mCRPC), the cancer stops
responding to hormone treatment, and it is found in other
parts of the body. It can spread to nearby lymph nodes,
bones, the bladder, rectum, liver, lungs, and maybe the
brain.

Metastatic insulinoma

Metastatic insulinoma: A rare form of pancreatic cancer that causes excessive secretion of the hormone insulin and can spread to other parts of the body (metastasis).

Metastatic Melanoma

Metastatic melanoma is a term used when melanoma cells of any kind (cutaneous, mucosal or ocular) have spread through the lymph nodes to distant sites in the body and/or to the body's organs. The most dangerous aspect of melanoma is its ability, in later stages, to spread (or metastasize) to other parts of the body.

Three groups of patients are identified: those with cutaneous, nodal, or gastrointestinal tract metastases; those with isolated pulmonary metastases; and those with liver, brain, or bone metastases.

Metastatic squamous neck cancer with occult primary

Metastatic squamous neck cancer with occult primary: A type of cancer that occurs in the neck and has spread (metastasized) to the lymph nodes from a primary source that has not been able to be determined. Squamous cells are cells that line hollow organs as well as the skin and throat.

Metatarsus adductus

Metatarsus adductus is a foot deformity. The bones in the middle of the foot bend in toward the body

Metatrophic dysplasia

Metatrophic dysplasia: A very rare form of dwarfism involving short limbs and a long trunk. Less than 100 cases of the condition have been reported.

Metatropic dwarfism

Metatropic dwarfism is a severe skeletal dysplasia characterized by extremely small stature with short arms and legs. Other characteristics of this disorder are a narrow thorax, short ribs, and kyphoscoliosis (backward and sideways curvature of the spinal column) which develops into short trunk dwarfism. This condition, caused by mutations in the TRPV4 gene, may be inherited in either an autosomal dominant or autosomal recessive manner.

Methionine adenosyl transferase deficiency

Methionine adenosyltransferase deficiency: A rare inborn error of metabolism characterized by high methionine levels in the blood due to an enzyme deficiency (methionine adenosyltransferase). Most cases are asymptomatic but severe cases with very low enzyme activity can cause neurological symptoms.

Methylcobalamin deficiency cbl G type

Methylcobalamin deficiency cbl G type: An inherited organic acid disorder where an enzyme deficiency (cbl G) impairs the body's ability to break down certain proteins consumed in the diet. This results in a buildup of homocystine which results in harmful affects.

Methylcobalamin deficiency- cbl E complementation type

Methylcobalamin deficiency, cbl E complementation type: An inherited organic acid disorder where an enzyme deficiency (cbl E) impairs the body's ability to break down cobalamin in the diet. This results in a buildup of homocystine which results in harmful affects.

Methylenetetrahydrofolate reductase deficiency

Methylene tetrahydrofolate reductase deficiency: A inborn error of metabolism where an inherited deficiency of methylene tetrahydrofolate reductase causes symptoms of ranging severity - from asymptomatic to severe neurological degeneration and premature death.

Methylmalonic acidemia

 Methylmalonic acidemia (MMA, also called methylmalonic aciduria), first characterized by Oberholzer et al. in 1967, is an autosomal recessive metabolic disorder. It is a classical type of organic acidemia. The result of this condition is the inability to properly digest specific fats and proteins, which in turn leads to a buildup of a toxic level of methylmalonic acid in the blood.

Methylmalonic acidemia stems from several genotypes, all forms of the disorder usually diagnosed in the early neonatal period, presenting progressive encephalopathy, and secondary hyperammonemia. The disorder can result in death if undiagnosed or left untreated. It is estimated that this disorder has a frequency of 1 in 48,000 births, though the high mortality rate in diagnosed cases make exact determination difficult.

Methylmalonic acidemias are found with an equal frequency across ethnic boundaries


Methylmalonic acidemia with homocystinuria

MMA+HCU stands for “methylmalonic acidemia with homocystinuria”. It is one type of organic acid disorder. People with MMA+HCU have problems breaking down and using certain amino acids and fatty acids from the food they eat.

Methylmalonic aciduria cblA type

MMA stands for “methylmalonic acidemia”. It is one type of organic acid disorder. People with MMA have problems breaking down and using certain amino acids and fatty acids from the food they eat.