Congenital disorder

Congenital disorder involves defects in or damage to a developing fetus. It may be the result of genetic abnormalities, the intrauterine (uterus) environment, errors of morphogenesis, or a chromosomal abnormality. The outcome of the disorder will further depend on complex interactions between the pre-natal deficit and the post-natal environment.^[1] Animal studies indicate that mother's (and possibly father's) diet, vitamin intake, and glucose levels prior to ovulation and conception have long-term effects on fetal growth and adolescent and adult disease.^[2] Congenital disorders vary widely in causation and abnormalities. Any substance that causes birth defects is known as a teratogen. The older term congenital [2] disorder does not necessarily refer to a genetic disorder despite the similarity of the words.

Classification

Much of the language used for describing congenital conditions predates genomic mapping, and structural conditions are often considered separately from other congenital conditions. It is now known that many metabolic conditions may have subtle structural expression, and structural conditions often have genetic links. Still, congenital conditions are often classified in a structural basis, organized when possible by primary organ system affected.

Primarily structural

Several terms are used to describe congenital abnormalities. (Some of these are also used to describe noncongenital conditions, and more than one term may apply in an individual condition.)

• A congenital physical anomaly is an abnormality of the structure of a body part. An anomaly may or may not be perceived as a problem condition. Many, if not most, people have one or more minor physical anomalies if examined carefully. Examples of minor anomalies can include curvature of the 5th finger (clinodactyly), a third nipple, tiny indentations of the skin near the ears (preauricular pits), shortness of the 4th metacarpal or metatarsal bones, or dimples over the lower spine (sacral dimples). Some minor anomalies may be clues to more significant internal abnormalities.

• Birth defect is a widely-used term for a congenital malformation, i.e. a congenital, physical anomaly which is recognizable at birth, and which is significant enough to be considered a problem. According to the CDC most birth defects are believed to be caused by a complex mix of factors including genetics, environment, and behaviors,^[1] though many birth defects have no known cause.

• A congenital malformation is a congenital physical anomaly that is deleterious, i.e. a structural defect perceived as a problem. A typical combination of malformations affecting more than one body part is referred to as a malformation syndrome.

• Some conditions are due to abnormal tissue development:
  • A malformation is associated with a disorder of tissue development.^[3] Malformations often occur in the first trimester.
  • A dysplasia is a disorder at the organ level that is due to problems with tissue development.^[3]

• It is also possible for conditions to arise after tissue is formed:
  • A deformation is a condition arising from mechanical stress to normal tissue.^[3] Deformations often occur in the second or third semester, and can be due to oligohydramnios.
• A disruption involves breakdown of normal tissues.^[3]

• When multiple effects occur in a specified order, it is known as a sequence. When the order is not known, it is a syndrome.

Other

• Genetic disorders or diseases are all congenital, though they may not be expressed or recognized until later in life. Genetic diseases may be divided into single-gene defects, multiple-gene disorders, or chromosomal defects. Single-gene defects may arise from abnormalities of both copies of an autosomal gene (a recessive disorder) or of only one of the two copies (a dominant disorder). Some conditions result from deletions or abnormalities of a few genes located contiguously on a chromosome. Chromosomal disorders involve the loss or duplication of larger portions of a chromosome (or an entire chromosome) containing hundreds of genes. Large chromosomal abnormalities always produce effects on many different body parts and organ systems.

• A congenital metabolic disease is also referred to as an inborn error of metabolism. Most of these are single gene defects, usually heritable. Many affect the structure of body parts but some simply affect the function.

• Other well defined genetic conditions may affect the production of hormones, receptors, structural proteins, and ion channels.

Causes

Antibiotics

Use of antibiotics around the time of conception, particularly sulfonamides and nitrofurantoin are associated with major birth defects. Whether or not this association is causal has not been determined.^[4]

Petroleum

Petroleum (oil) and petroleum distillates cause birth defects.^[5]

Epidemiology

Disability-adjusted life year for congenital anomalies per 100,000 inhabitants in 2004.^[6]

     no data      less than 160      160-240      240-320      320-400      400-480      480-560      560-640      640-720      720-800      800-900      900-950      more than 950

Cell division errors can be due to a lack of nutrients or availability of atomic building blocks, or the presence of toxins that impede normal growth. Division errors which occur very early in the development of a multicellular organism can result in large scale structural and functional differences in the organism's final shape. For example it is now understood that a lack of folic acid in the diet of a mother can cause cellular neural tube deformities that result in Spina Bifida.

External physical shocks or constrainment due to growth in a restricted space, may result in unintended deformation or separation of cellular structures resulting in an abnormal final shape or damaged structures unable to function as expected.

For multicellular organisms that develop in a womb, the physical interference or presence of other similarly developing organisms such as twins can result in the two cellular masses being integrated into a larger whole, with the combined cells attempting to continue to develop in a matter that satisfies the intended growth patterns of both cell masses. The two cellular masses can compete with each other, and may either duplicate or merge various structures. This results in conditions such as conjoined twins, and the resulting merged organism may die at birth when it must leave the life-sustaining environment of the womb and must attempt to sustain its biological processes independently.

See also

• Congenital abnormality
• List of congenital disorders
• ICD-10 Chapter Q: Congenital malformations, deformations and chromosomal abnormalities
• List of ICD-9 codes 740-759: Congenital anomalies
• Mitochondrial disease
• March of Dimes

References

External links

• CDC’s National Center on Birth Defects and Developmental Disabilities
• Comprehensive coverage of congenital disorders and birth defects at Answers.com
• Congenital Anomalies, official journal of the Japanese Teratology Society
• Stop CMV - The CMV Action Network