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Center for Congenital and Inherited Disorders

Congenital and Inherited Disorders

Patient Education Learning Modules

The following list of disorders is a small list and by no means encompasses all genetic disorders. The disorders listed are ones that are mentioned throughout our web site

Abdominal wall defects are birth defects of the abdominal wall. There are two types of abdominal wall defects, omphalocele and gastroschisis.

    Omphalocele results from the incomplete closure of the umbilicus. The birth defect involves the protrusion of abdominal organs such as the intestine and liver into the umbilical cord. A membrane always covers an omphalocele, although sometimes this membrane may rupture. A ruptured omphalocele may be mistaken for a gastroschisis. Infants with omphalocele may have other birth defects, including chromosomal abnormalities.

    Gastroschisis does not involve the umbilicus. The birth defect results from the protrusion of intestine and sometimes liver outside of the abdomen. This defect usually occurs to the right of the umbilicus and never includes a covering membrane. Infants with gastroschisis tend not to have other birth defects. Gastroschisis is not associated with chromosomal abnormalities.

Becker muscular dystrophy (BMD) is an X-linked inherited disorder of progressive muscle weakness and wasting. Becker muscular dystrophy is similar to the Duchenne muscular dystrophy except that the progression of symptoms is much slower. Onset of BMD is usually adolescence or adulthood. The disease is caused by changes in the gene that makes the muscle protein dystrophin. People with Becker have reduced levels of dystrophin. Without normal levels of dystrophin, muscle cells gradually die.

Biotinidase deficiency is an inherited disorder caused by the lack of an enzyme called biotinidase, which normally allows the body to recycle biotin. Biotin is essential for normal metabolism and because humans do not synthesize biotin, the ability to use and reuse all available biotin is critical. Onset of symptoms occurs anywhere from two weeks to two years of age. Symptoms of untreated biotinidase deficiency include seizures, low muscle tone, developmental delay, hearing loss, vision problems and recurrent infections. Early treatment with biotin supplementation results in normal growth and development. Periodic vision and hearing evaluations are recommended.

Charcot-Marie-Tooth (CMT) is the most commonly inherited neurological disorder. The defect is in the nerves that control the muscles. CMT is found world-wide in all races and ethnic groups. CMT patients slowly lose normal use of their feet/legs and hands/arms as nerves to the extremities degenerate and the muscles in the extremities become weakened because of the loss of stimulation by the affected nerves. Many patients also have some loss of sensory nerve function. CMT isn't life-threatening and almost never affects brain function. It is not contagious, but it is hereditary.

Cleft lip is a separation of the two sides of the lip. The separation creates an opening in the upper lip between the mouth and the nose and often includes the bones of the upper jaw and/or upper gum. A cleft occurring on one side of the lip is called a unilateral cleft lip. A cleft occurring on both sides is called bilateral cleft lip. Cleft lip and palate is the fourth most common birth defect in the United States.

Cleft palate is an opening in the roof of the mouth that occurs when the two sides of the palate fail to fuse together. An individual can have only a cleft palate or both a cleft palate and cleft lip.

Congenital adrenal hyperplasia is a group of inherited disorders caused by abnormalities in specific enzymes of the adrenal gland. Ninety percent of congenital adrenal hyperplasia cases are caused by the lack of the enzyme 21-hydroxylase. The enzyme deficiency prevents the body from making hormones necessary for the normal functioning of the body. Increased production of a male hormone called androgen can result in ambiguous genitalia and rapid growth and skeletal maturation in childhood. Babies with untreated congenital adrenal hyperplasia may develop vomiting and severe dehydration, which can be life threatening.

Congenital heart defects account for twenty percent of all birth defects observed in liveborns. Malformations may occur in any region of the heart and the degree of severity is variable. Congenital heart defects are the leading cause of premature death in infants born with birth defects. Some heart malformations are the result of an underlying chromosome abnormality or genetic syndrome. Familial factors, exposure to some drugs or medications, drinking alcohol during pregnancy or a combination of factors can cause heart defects. However, for many congenital heart defects the cause can't be determined.

Congenital hypothyroidism results from a deficiency in the production of thyroid hormone. Poor growth, mental retardation, deafness and neurological abnormalities can result without prompt identification and treatment. Early diagnosis and adequate treatment with thyroxine within the first weeks of life results in normal growth and intelligence.

Congenital muscular dystrophy is a group of autosomal recessively inherited neuromuscular disorders. Infants born with a congenital muscular dystrophy have joint contractures, very poor muscle tone and generalized muscle weakness. Brain and heart abnormalities may also be present in some forms of congenital muscular dystrophy. Clinical symptoms are nonprogressive or slowly progressive.

Cystic fibrosis is an inherited chronic disease that affects the lungs and digestive system of about 30,000 children and adults in the United States (70,000 worldwide). A defective gene and its protein product cause the body to produce unusually thick, sticky mucus that:

  • clogs the lungs and leads to life-threatening lung infections; and
  • obstructs the pancreas and stops natural enzymes from helping the body break down and absorb food.

People with CF can have a variety of symptoms, including:

  • very salty-tasting skin;
  • persistent coughing, at times with phlegm;
  • frequent lung infections;
  • wheezing or shortness of breath;
  • poor growth/weight gain in spite of a good appetite; and
  • frequent greasy, bulky stools or difficulty in bowel movements

Cystic fibrosis is the most common fatal genetic disease of Caucasians. It also occurs in other ethnic groups with lesser frequency. A recessive trait, the gene frequency in those of Northern European descent is estimated to be as high as 5% of the population. There are no adverse effects for carriers of a CF mutation; the potential for disease only occurs when a CF mutation is inherited from both parents. Although a specific cure is still wanting, aggressive treatment at specialized Cystic Fibrosis Centers has increased the average survival from less than 10 years when the disease was first identified over 40 years ago, to 16 years only about 30 years ago, to its current mean of the mid-thirties. Quality of life has similarly progressed during this period.

Down syndrome is the most common chromosome disorder. Typically, an individual has 23 pairs of chromosomes. The presence of a third or portion of an third chromosome 21 causes Down syndrome. The extra chromosome material is responsible for characteristic facial features, mental retardation, low muscle tone and associated intestinal and heart abnormalities. A woman's chances of having a baby with Down syndrome increases with advancing maternal age and significantly increases for women 35 years and older. Down syndrome can be prenatally diagnosed.

Duchenne muscular dystrophyis an X-linked inherited disorder of progressive and rapid muscle weakness and wasting. Onset is in early childhood at about 2 to 6 years of age. The disease is caused by changes in the gene that makes the muscle protein dystrophin. Individuals with Duchenne do not produce any dystrophin. Without functional dystrophin, muscle cells gradually die.

Fragile X syndrome Fragile X is a family of genetic conditions, which can impact individuals and families in various ways. These genetic conditions are related in that they are all caused by gene changes in the same gene, called the FMR1 gene. Fragile X syndrome (FXS) is the most common cause of inherited mental impairment. This impairment can range from learning disabilities to more severe cognitive or intellectual disabilities (sometimes referred to as mental retardation). FXS is the most common known cause of autism or "autistic-like" behaviors. Symptoms also can include characteristic physical and behavioral features and delays in speech and language development. Fragile X can be passed on in a family by individuals who have no apparent signs of this genetic condition. In some families a number of family members appear to be affected, whereas in other families a newly diagnosed individual may be the first family member to exhibit symptoms. Fragile X syndrome occurs in approximately 1/4000 individuals.

Friedreich's ataxia is an inherited neurodegenerative disorder with progressive loss of muscle strength and control. Symptoms typically begin in the first and second decade of life and include muscle weakness, loss of coordination of arm and leg movement, curvature of the spine, vision impairment, hearing loss and slurred speech. Individuals with Friedreich's ataxia may develop cardiomyopathy and diabetes. Symptoms are secondary to the death of cells in certain parts of the nervous system. Intelligence and mental capability, however, are not affected.

Galactosemia is an inheritable disorder caused by a lack of the GALT (gactose-1-phosphate uridyl transferase) enzyme needed to break down the milk sugar galactose. The conversion of galactose to glucose is critical for normal body functioning. Glucose is the body's source of energy. Without early diagnosis and strict dietary treatment, life-threatening complications, mental retardation, and blindness can occur. Clinical symptoms may present as early as the first week of life.

Hemoglobinopathies are inherited red blood cell disorders caused by abnormalities in the structure or production of hemoglobins. Hemoglobins are molecules within red blood cells that carry oxygen from the lungs to the rest of the body. There are over 500 different types of hemoglobin. Hemoglobin A or normal adult hemoglobin is the most common type. Sickle cell anemia is one of the most common hemoglobinopathies. The red cells of an individual with this disorder contain only hemoglobin S and no normal hemoglobin A. Their red blood cells sickle and clog small vessels, disrupting the delivery of oxygen to the body tissues. Sickle cell anemia can cause pain, infection, lung complications, gallstones, stroke and other medical problems. There are hemoglobin types such as hemoglobin C, D or E that in combination with hemoglobin S can result in different forms of sickle cell disease. Good medical care, family education, and antibiotics can minimize life-threatening complications.

Krabbe disease Krabbe disease is a rare, inherited degenerative disorder of the central and peripheral nervous systems. It is characterized by the presence of globoid cells (cells that have more than one nucleus), the breakdown of the nerve's protective myelin coating, and destruction of brain cells. Krabbe disease is one of a group of genetic disorders called the leukodystrophies. . The disease most often affects infants, with onset before age 6 months, but can occur in adolescence or adulthood. Symptoms include irritability, unexplained fever, limb stiffness, seizures, feeding difficulties, vomiting, and slowing of mental and motor development. Other symptoms include muscle weakness, spasticity, deafness, and blindness. There is no cure for Krabbe disease. Results of a very small clinical trial of patients with infantile Krabbe disease found that children who received umbilical cord blood stem cells from unrelated donors prior to symptom onset developed with little neurological impairment. Results also showed that disease progression stabilized faster in patients who receive cord blood compared to those who receive adult bone marrow. Bone marrow transplantation has been shown to benefit mild cases early in the course of the disease. Generally, treatment for the disorder is symptomatic and supportive. Physical therapy may help maintain or increase muscle tone and circulation.

Limb-girdle muscular dystrophy is a group of inherited disorders with muscle weakness of the hip girdle and the lower extremities. Onset of symptoms may occur in late childhood or be delayed until early adulthood. Progressive of the disorder is slow.

Medium chain acyl-CoA dehydrogenase deficiency is a rare inherited fatty oxidation disorder caused by a lack of an enzyme required to convert fat into energy. This energy keeps the body running whenever it depletes its main energy source glucose. It is crucial that individuals with medium chain acyl-CoA dehydrogenase deficiency avoid going for long periods of time without eating. Prolonged fasting can lead to very low blood sugar levels, seizures, coma, and even death.

Myasthenia gravis is an autoimmune disorder characterized by rapid muscle fatigue, drooping of the upper eyelids, and facial weakness. If untreated, the disorder can be progressive. The disorder is generally nonfamilial; however, there is a rare inheritable congenital form of myasthenia gravis. About fifteen percent of babies born to mothers with myasthenia gravis have a transient form of the disorder.

Neural tube defects are birth defects of the brain and the spinal cord. The brain and spinal cord begin developing during the first six weeks of pregnancy from a structure called the neural tube. The top of this tube develops into the head and brain and rest becomes the spinal cord. The neural tube must close properly for the brain and spine to develop normally. Most open neural tube defects can be detected prenatally. The two most common types of open neural tube defects are anencephaly and spina bifida.

    Anencephaly is a fatal condition that occurs when the skull and brain do not develop normally.

    Spina bifida results from the incomplete closure of the spine. Clinical severity depends largely on the extent and exact location of the opening. Infants with spina bifida may have medical problems involving weakness or paralysis of the legs, problems with bowel and bladder control, chronic infection, hydrocephalus (water on the brain), and sometimes mental retardation. Medical care, corrective surgery and physical therapy can help to maximize the potential capabilities of these children, many of whom are able to lead very productive lives.

Phenylketonuria is an inherited disorder caused by the lack of an enzyme needed to breakdown the protein phenylalanine. Phenylalanine is present in almost all foods. Without early diagnosis and strict adherence to a special diet, brain damage and mental retardation can occur.

Pompe disease Pompe disease is a rare (estimated at 1 in every 40,000 births), inherited and often fatal disorder that disables the heart and muscles. Early onset (or infantile) Pompe disease is the result of complete or near complete deficiency of GAA. Symptoms begin in the first months of life, with feeding problems, poor weight gain, muscle weakness, floppiness, and head lag. Respiratory difficulties are often complicated by lung infections. The heart is grossly enlarged. More than half of all infants with Pompe disease also have enlarged tongues. Most babies with Pompe disease die from cardiac or respiratory complications before their first birthday. Late onset (or juvenile/adult) Pompe disease is the result of a partial deficiency of GAA. The onset can be as early as the first decade of childhood or as late as the sixth decade of adulthood. The primary symptom is muscle weakness progressing to respiratory weakness and death from respiratory failure after a course lasting several years. The heart may be involved but it will not be grossly enlarged. A diagnosis of Pompe disease can be confirmed by screening for the common genetic mutations or measuring the level of GAA enzyme activity in a blood sample -- a test that has 100 percent accuracy.

Severe Combined Immune Deficiency (SCID) SCID is a group of very rare-and potentially fatal-inherited disorders related to the immune system. The immune system normally fights off attacks from dangerous bacteria and viruses. People with SCID have a defect in their immune system that leaves them vulnerable to potentially deadly infections. There are several types of SCID. Symptoms usually appear in the first few months of life. Because the immune system cannot protect the baby's body, babies with the disorder tend to get one infection after another. Some of these bacterial infections may be life-threatening, including pneumonia (lung infection), meningitis (brain infection), and sepsis (blood infection). To make matters worse, SCID patients often don't respond to the antibiotics used to treat bacterial infections. They may suffer more frequently from ear infections, sinus infections, a chronic cough, and rashes on the skin. Early diagnosis of SCID is very important, because without quick treatment, children with the disease aren't likely to live past age 2.Children with SCID must be careful to stay away from germ-rich environments (such as day care centers and crowded shopping malls) where they could pick up a potentially life-threatening infection. The most effective treatment is a bone marrow transplant. Unspecialized stem cells (that will form blood and immune cells) are taken from the bone marrow of a healthy donor and injected into the SCID patient. Ideally, these new cells will stimulate the production of the needed immune cells. Transplants done within the first few months of life are most successful. The tissue must be "matched" to the patient, however, which can limit the usefulness of this therapy. Siblings make the best donors as their cells likely contain a similar genetic makeup.

Stickler syndrome (formerly known as Hereditary Progressive Arthro-Ophthalmopathy) is an inherited autosomal dominant genetic disorder. About 1 in 7500 people have Stickler syndrome, but it is suspected that this condition is under-diagnosed. Stickler syndrome affects connective tissues throughout the body, most notably the eyes, ears, face and joints. Sticklers is the most common cause of retinal detachments in children, and is the most common connective tissue disorder.

New materials for both health care professionals and patients/families are available on the Stickler Involved People (SIP) website.

  • Under the tab "Physician's Overview", scroll down to find the link to the latest chapter on Stickler syndrome as published in Management of Genetic Syndromes, Third Edition, 2009. This reference gives a thorough review of all Stickler symptoms and related management of those health issues. It is a good resource for physicians and patients.
  • There is also a new offering area: IEP & 504 Plan Help, which includes a thorough review of these types of plans and how they might assist those with Stickler syndrome in the school setting. Also available on the web site is "College Bound Considerations for Students with Stickler Syndrome".
  • And finally,a separate website - now offers viewing of the 30 minute video, Stickler Syndrome - Learning the Facts, for free! The video includes information pertinent to both physicians and their patients. Check it out!

Spinal muscular atrophy comprises a group of inherited disorders involving degeneration of the nerves controlling voluntary muscle movement. Symptoms include progressive muscle atrophy and weakness, loss of tendon reflexes, contractures, and uncoordinated skeletal muscle contraction. Intelligence is not affected. Spinal muscular atrophy is classified into three subtypes: SMA type I or Werdnig-Hoffman disease, SMA II (intermediate type) and SMA III or Kugelberg-Welander disease. Classification is based on age of onset, severity of muscle weakness and clinical course.

Trisomy 18 is a chromosome disorder caused by the presence of a third or portion of an third chromosome 18. Typically, an individual has 23 pairs of chromosomes. The extra chromosome material is responsible for severe mental retardation, heart defects, and other health problems. A woman's chances of having a baby with Trisomy 18 increases with advancing maternal age and significantly increases for women 35 years and older. Trisomy 18 can be prenatally diagnosed.


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