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Phenylketonuria (PKU). This metabolic condition results from the lack of an enzyme in the liver that converts phenylalanine to tyrosine. Phenylalanine is one of the essential amino acids found in all protein foods. Incidence is 1:12,000 and although it is found in all ethnic groups, PKU is most prevalent among people of Irish or Scottish descent. Symptoms include severe mental retardation, seizures, autism-like disorders, and a peculiar odor. Lifespan is reduced. Treatment consists of lifelong dietary management and counseling.

Galactosemia. This is an inherited disorder of galactose metabolism. Galactose is the major sugar found in milk. Incidence is 1:50,000 and has no reported ethnic or racial variability. Symptoms include severe mental retardation, overwhelming systemic infections, failure to thrive, vomiting, liver disease, and cataracts. Untreated galactosemia is generally fatal. Treatment requires elimination of milk and milk products (all products containing lactose) from the diet.

Maple syrup urine disease (MSUD). MSUD is caused by abnormal metabolism of three branched-chain amino acids: leucine, isoleucine, and valine. Although the overall incidence of the disorder is 1:200,000, it is about 1:760 among Mennonites. Symptoms include an odor of maple syrup in the urine, poor feeding, lethargy, coma, and mental retardation. If not treated, death commonly occurs within three months of birth. Treatment requires dietary restriction of branched-chain amino acids, necessitating a complicated formula and intensive monitoring.

Homocystinuria. The most common cause of homocystinuria is a deficiency in the enzyme cystathionine [Beta]-synthase. Incidence is 1:200,000, but prevalence is 1:82,000 in Great Britain, Ireland, and Australia. Among the symptoms are thromboembolism, optic lens dislocation (which may occur even with treatment), scoliosis, osteoporosis, mental retardation, seizures, and psychiatric disturbances. Approximately 50 percent of untreated individuals die before age 25. Treatment may include a methionine-restricted, cystine-supplemented diet, as well as large doses of Vitamin B6.

Congenital hypothyroidism. This disorder is caused by inadequate production of thyroxine, a thyroid hormone. Incidence is approximately 1:4,000. Symptoms include mental retardation, growth failure, deafness, neurologic abnormalities, and slow metabolism. Treatment is levothyroxine, thyroid hormone replacement therapy, given orally.

Biotinidase deficiency. A deficiency of biotin, part of the Vitamin B complex, leading to multiple carboxylase deficiency. Incidence is 1:87,000. Symptoms include seizures, hypotonia, immune system impairment, skin rashes, hair loss, hearing loss, and mental retardation. Treatment is oral biotin supplementation.

Congenital adrenal hyperplasia (CAH). The most common form (more than 90 percent of all recognized cases) results from 21-hydroxylase deficiency. Incidence is 1:12,000, but may be as high as 1:5,000 among those of Italian background. CAH causes increased androgen production, resulting in ambiguous genitalia and virilization in girls and early virilization in boys. Other symptoms are accelerated skeletal maturation and ultimate short stature. Treatment is glucocorticosteroids.

Hemoglobinopathies. A group of disorders characterized by abnormal hemoglobin [Beta] chains: sickle-cell disease and thalassemia are two. Overall incidence of hemoglobinopathies in the US is 1:58,000. Sickle cell is most commonly found in African-Americans and has an incidence of about 1:600. Thalassemia is most likely to affect people with eastern Mediterranean (Greek, Arabic, Italian) or East Indian ancestry. Symptoms are lifelong hemolytic anemia, abnormally shaped blood cells leading to acute and chronic tissue damage, intermittent cardiac crises, enlarged spleen, and sepsis. Ongoing therapy is penicillin prophylaxis and vigilant treatment of infections. Aggressive pain management, management of dehydration and acidosis, blood transfusions, and oxygen are all utilized for acute episodes.

Cystic fibrosis. An inherited disorder that affects the mucus-producing glands. Mucus is thick, and can obstruct air passages in the lungs. It also causes dysfunction of the sweat and salivary glands, and blocks the enzymes secreted by the pancreatic duct, resulting in incomplete digestion. Incidence is 1:2,500 white live births and 1:17,000 African American live births. Cystic fibrosis can cause lung disease, failure to grow, clubbed fingers and toes, muscular weakness, and visual impairment. Treatment includes high doses of ibuprofen, antibiotics for pulmonary disease, and clearing of the airways with intermittent aerosol therapy.

Tyrosinemia. A metabolic disorder that causes elevated levels of tyrosine, an amino acid present in most proteins. The incidence is 1:100,000 live births, with both sexes affected equally. Symptoms include failure to thrive, vomiting, diarrhea, and a cabbage-like odor. Other symptoms include enlarged liver, edema, and risk of hemmorhagic diseases. If untreated, tyrosinemia is fatal within the first year of life. Treatment includes dietary restrictions.

Toxoplasmosis. An infectious disease that, if it occurs congenitally, can cause severe fetal disease. The incidence of congenital toxoplasmosis is 0.25:100,000 to 5:100,000 live births. Symptoms can include microcephaly (small head size), hydrocephalus, vision impairment, mental retardation, seizures, anemia, jaundice, and rash. Treatment, when indicated, includes antibiotics such as pyrimethamine and sulfadiazine.

MCAD. Medium-chain Acyl-CoA dehydrogenase (MCAD) deficiency is an inherited enzyme deficiency. The incidence is 1:50,000 live births, with males and females affected equally. Symptoms include intermittent hypoglycemia and metabolic acidosis, sometimes resulting in coma. Fatty changes in the liver may also occur. Treatment involves prevention of prolonged fasting to prevent symptoms.

G6PD. Glucose-6-phosphate-dehydrogenase (G6PD) is an enzyme that is necessary for glucose metabolism and the preservation of red blood cells. G6PD deficiency is the most common genetic enzyme deficiency, occurring most often in tropical and subtropical Asia, tropical Africa, areas of the Mediterranean, the Middle East, and New Guinea. It can cause premature destruction of red blood cells (hemolytic anemia) when an affected individual is exposed to certain medications, chemicals, foods, or pollen. Severity of the condition is extremely variable. Treatment involves restricting exposure to pathogens that cause a reaction.

HIV. Human immunodeficiency virus (HIV) is an immunosuppressive disorder resulting from viral infection and destruction of the body's T-cells. The virus eventually progresses to acquired immunodeficiency syndrome (AIDS). Incidence in newborns varies according to viral status of the mother. Initially, HIV is asymptomatic. Young children, however, have a much shorter incubation period and generally develop symptoms within two years. Symptoms include wasting, fatigue, fever, oral thrush, rashes, and super-infection with opportunistic organisms. Treatment involves chronic use of antiviral drugs to slow progression of the virus and allow the immune system to recover. Infections are treated with antibiotics and antifungals.
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Publication:The Exceptional Parent
Article Type:Glossary
Date:Aug 1, 2000
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