Congenital disorder

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This article is about congenital disorders in humans. For animals, see Teratology.
Congenital disorders
Classification and external resources
MeSH D009358

A congenital disorder, or congenital disease, is a condition existing at birth and often before birth, or that develops during the first month of life (neonatal disease), regardless of causation. Of these diseases, those characterized by structural deformities are termed "congenital anomalies" and involve defects in or damage to a developing fetus.

A congenital disorder may be the result of genetic abnormalities, the intrauterine (uterus) environment, errors of morphogenesis, infection, or a chromosomal abnormality. The outcome of the disorder will depend on complex interactions between the pre-natal deficit and the post-natal environment.[1] Animal studies indicate that the mother's (and possibly but less probably the 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. Some disorders can be detected before birth through prenatal diagnosis (screening).

The term "congenital"[3] disorder does not necessarily refer to a genetic disorder despite the similarity of the words.

Some congenital conditions are idiopathic, and sometimes the word "congenital" is used synonymously with "idiopathic"; but careful usage prefers to reserve the word "congenital" for conditions to which the literal sense of the word applies (that is, those whose pathophysiology has existed since the neonatal period).

Classification[edit]

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[edit]

Structural congenital disorder
Classification and external resources
ICD-10 Chapter-Q
MeSH D000013

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.)

Terminology[edit]

  • 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. An example of a birth defect is cleft palate.
  • 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.[4] Malformations often occur in the first trimester.
    • A dysplasia is a disorder at the organ level that is due to problems with tissue development.[4]
  • It is also possible for conditions to arise after tissue is formed:
    • A deformation is a condition arising from mechanical stress to normal tissue.[4] Deformations often occur in the second or third trimester, and can be due to oligohydramnios.
  • A disruption involves breakdown of normal tissues.[4]
  • When multiple effects occur in a specified order, it is known as a sequence. When the order is not known, it is a syndrome.

Examples of primarily structural congenital disorders[edit]

A limb anomaly is called a dysmelia. These include all forms of limbs anomalies, such as amelia, ectrodactyly, phocomelia, polymelia, polydactyly, syndactyly, polysyndactyly, oligodactyly, brachydactyly, achondroplasia, congenital aplasia or hypoplasia, amniotic band syndrome, and cleidocranial dysostosis.

Congenital anomalies of the heart include patent ductus arteriosus, atrial septal defect, ventricular septal defect, and tetralogy of fallot. Helen Taussig has been a major force in research on congenital anomalies of the heart.[5]

Congenital anomalies of the nervous system include neural tube defects such as spina bifida, meningocele, meningomyelocele, encephalocele and anencephaly. Other congenital anomalies of the nervous system include the Arnold-Chiari malformation, the Dandy-Walker malformation, hydrocephalus, microencephaly, megencephaly, lissencephaly, polymicrogyria, holoprosencephaly, and agenesis of the corpus callosum.

Congenital anomalies of the gastrointestinal system include numerous forms of stenosis and atresia, and imperforate.

Congenital anomalies of the kidney and urinary tract (CAKUT) include renal parenchyma, kidneys, and urinary collecting system.[6]

Defects can be bilateral or unilateral, and different defects often coexist in an individual child

Primarily metabolic[edit]

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[edit]

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

Causes[edit]

Toxic substances[edit]

Substances whose toxicity can cause congenital disorders are called "teratogens", and include certain pharmaceutical and recreational drugs in pregnancy as well as many environmental toxins in pregnancy.

A review published in 2010 identified 6 main teratogenic mechanisms associated with medication use: folate antagonism, neural crest cell disruption, endocrine disruption, oxidative stress, vascular disruption and specific receptor- or enzyme-mediated teratogenesis.[7]

It is estimated that 10% of all birth defects are caused by prenatal exposure to a teratogenic agent.[8] These exposures include, but are not limited to, medication or drug exposures, maternal infections and diseases, and environmental and occupational exposures. Teratogen-caused birth defects are potentially preventable. Studies have shown that nearly 50% of pregnant women have been exposed to at least one medication during gestation.[9] An additional study found that of 200 individuals referred for genetic counseling for a teratogenic exposure, 52% were exposed to more than one potential teratogen.[10]

Isotretinoin (13-cis-retinoic-acid; brand name Roaccutane), which is often used to treat severe acne, is such a strong teratogen that just a single dose taken by a pregnant woman may result in serious birth defects. Because of this effect, most countries have systems in place to ensure that it is not given to pregnant women, and that the patient is aware of how important it is to prevent pregnancy during and at least one month after treatment. Medical guidelines also suggest that pregnant women should limit vitamin A intake to about 700 μg/day, as it has teratogenic potential when consumed in excess.[11][12]

Infections[edit]

A vertically transmitted infection is an infection caused by bacteria, viruses or, in rare cases, parasites transmitted directly from the mother to an embryo, fetus or baby during pregnancy or childbirth. It can occur when the mother gets an infection as an intercurrent disease in pregnancy.

Lack of nutrients[edit]

Further information: Nutrition in pregnancy

For example, a lack of folic acid in the diet of a mother can cause cellular neural tube deformities that result in spina bifida.

Physical restraint[edit]

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. An example is Potter syndrome due to oligohydramnios.

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.

Genetic causes[edit]

Main article: Genetic disorder

Genetic causes of congenital anomalies include inheritance of abnormal genes from the parents, as well as new mutations in one of the germ cells that gave rise to the fetus.

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.

Unknown or multifactorial[edit]

Although significant progress has been made in identifying the etiology of some birth defects, approximately 65% have no known or identifiable cause.[8] These are referred to as sporadic, a term that implies an unknown cause, random occurrence regardless of maternal living conditions,[13] and a low recurrence risk for future children. For 20-25% of anomalies there seems to be a "multifactorial" cause, meaning a complex interaction of multiple minor genetic anomalies with environmental risk factors. Another 10-13% of anomalies have a purely environmental cause (e.g. infections, illness, or drug abuse in the mother). Only 12-25% of anomalies have a purely genetic cause. Of these, the majority are chromosomal anomalies.[14]

Role of radiation[edit]

For the survivors of the atomic bombing of Hiroshima and Nagasaki, who are known as the Hibakusha, no statistically demonstrable increase of birth defects/congenital malformations was found among their later conceived children, or found in the later conceived children of cancer survivors who had previously received radiotherapy.[15][16][17][18] The surviving women of Hiroshima and Nagasaki who were able to conceive, though exposed to substantial amounts of radiation, went on and had children with no higher incidence of abnormalities/birth defects than in the Japanese population as a whole.[19][20]

Epidemiology[edit]

Disability-adjusted life year for congenital anomalies per 100,000 inhabitants in 2004.[21]
  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

Congenital anomalies resulted in about 510,000 deaths globally in 2010.[22]

Many studies have found that the frequency of occurrence of certain congenital malformations depends on the sex of the child (table).[23][24][25][26][27] For example, pyloric stenosis occurs more often in males while congenital hip dislocation is four to five times more likely to occur in females. Among children with one kidney, there are approximately twice as many males, whereas among children with three kidneys there are approximately 2.5 times more females. The same pattern is observed among infants with excessive number of ribs, vertebrae, teeth and other organs which in a process of evolution have undergone reduction—among them there are more females. Contrarily, among the infants with their scarcity, there are more males. Anencephaly is shown to occur approximately twice as frequently in females.[28] The number of boys born with 6 fingers is two times higher than the number of girls.[29] Now various techniques are available to detect congenital anomalies in fetus before birth.[citation needed]

About 3% of newborns have a "major physical anomaly", meaning a physical anomaly that has cosmetic or functional significance.[30]

Physical congenital abnormalities are the leading cause of infant mortality in the United States, accounting for more than 20% of all infant deaths. Seven to ten percent of all children will require extensive medical care to diagnose or treat a birth defect.[31]

The sex ratio of patients with congenital malformations
Congenital anomaly Sex ratio, ♂♂:♀♀
Defects with female predominance
Congenital hip dislocation 1 : 5.2;[32] 1 : 5;[33] 1 : 8;[27] 1 : 3.7[34]
Cleft palate 1 : 3[33]
Anencephaly 1 : 1.9;[32] 1 : 2[28]
Craniocele 1 : 1.8[32]
Aplasia of lung 1 : 1.51[32]
Spinal herniation 1 : 1.4[32]
Diverticulum of the esophagus 1 : 1.4[32]
Stomach 1 : 1.4[32]
Neutral defects
Hypoplasia of the tibia and femur 1 : 1.2[32]
Spina bifida 1 : 1.2[34]
Atresia of small intestine 1 : 1[32]
Microcephaly 1.2 : 1[34]
Esophageal atresia 1.3 : 1;[32] 1.5 : 1[34]
Hydrocephalus 1.3 : 1[34]
Defects with male predominance
Diverticula of the colon 1.5 : 1[32]
Atresia of the rectum 1.5 : 1;[32] 2 : 1[34]
Unilateral renal agenesis 2 : 1;[32] 2.1 : 1[34]
Schistocystis 2 : 1[32]
Harelip 2 : 1;[33] 1.47 : 1[34]
Bilateral renal agenesis 2.6 : 1[32]
Congenital anomalies of the genitourinary system 2.7 : 1[27]
Pyloric stenosis, congenital 5 : 1;[33] 5.4 : 1[27]
Meckel's diverticulum More common in boys[32]
Congenital megacolon More common in boys[32]
All defects 1.22 : 1;[35] 1.29 : 1[27]
  • Data[27] obtained on opposite-sex twins. ** — Data[34] were obtained in the period 1983-1994.

P. M. Rajewski and A. L. Sherman (1976) have analyzed the frequency of congenital anomalies in relation to the system of the organism. Prevalence of men was recorded for the anomalies of phylogenetically younger organs and systems.[32]

In respect of an etiology, sexual distinctions can be divided on appearing before and after differentiation of male's gonads in during embryonic development, which begins from eighteenth week. The testosterone level in male embryos thus raises considerably.[36] The subsequent hormonal and physiological distinctions of male and female embryos can explain some sexual differences in frequency of congenital defects. It is difficult to explain the observed differences in the frequency of birth defects between the sexes by the details of the reproductive functions or the influence of environmental and social factors.

See also[edit]

References[edit]

  1. ^ a b Birth Defects Research. Centers for Disease Control and Prevention.
  2. ^ Gregory W. Rutecki (2010). "Pre-Prenatal Care: A Primary Care Primer on the Future". ConsultantLive.com. Retrieved 25 September 2010. 
  3. ^ Webster's Dictionary. 
  4. ^ a b c d Graham, John Whichello (2007). Smith's Recognizable Patterns of Human Deformation, 3rd Edition. Philadelphia: Saunders. p. 3. ISBN 0-7216-1489-2. 
  5. ^ http://www.answers.com/topic/helen-taussig
  6. ^ "Overview of congenital anomalies of the kidney and urinary tract (CAKUT)". UpToDate - Wolters Kluer Health. Retrieved 29 October 2012. 
  7. ^ van Gelder MM, van Rooij IA, Miller RK, Zielhuis GA, de Jong-van den Berg LT, Roeleveld N (January 2010). "Teratogenic mechanisms of medical drugs". Hum Reprod Update 16 (4): 378–94. doi:10.1093/humupd/dmp052. PMID 20061329. 
  8. ^ a b Ronan O'Rahilly, Fabiola Müller (2001). Human embryology & teratology. New York: Wiley-Liss. ISBN 0-471-38225-6. 
  9. ^ Bracken MB, Holford TR (1981). "Exposure to prescribed drugs in pregnancy and association with congenital malformations". Obstetrics and gynecology 58 (3): 336–44. PMID 7266953. 
  10. ^ King CR (1986). "Genetic counseling for teratogen exposure". Obstetrics and gynecology 67 (6): 843–6. doi:10.1097/00006250-198606000-00020. PMID 3703408. 
  11. ^ Hunt JR (1996). "Teratogenicity of high vitamin A intake". N. Engl. J. Med. 334 (18): 1197. doi:10.1056/NEJM199605023341814. PMID 8602195. 
  12. ^ Hartmann S, Brørs O, Bock J, et al. (2005). "Exposure to retinoic acids in non-pregnant women following high vitamin A intake with a liver meal". International journal for vitamin and nutrition research. Internationale Zeitschrift für Vitamin- und Ernährungsforschung. Journal international de vitaminologie et de nutrition 75 (3): 187–94. doi:10.1024/0300-9831.75.3.187. PMID 16028634. 
  13. ^ Bezerra Guimarães MJ, Marques NM, Melo Filho DA (2000). "[Infant mortality rate and social disparity at Recife, the metropolis of the North-East of Brazil]". Sante (in French) 10 (2): 117–21. PMID 10960809. 
  14. ^ Kumar, Abbas and Fausto, eds., Robbins and Cotran's Pathologic Basis of Disease, 7th edition, p.473.
  15. ^ http://apps.who.int/iris/bitstream/10665/78218/1/9789241505130_eng.pdf World Health Organization report. page 23 & 24 internal
  16. ^ http://jama.ama-assn.org/content/268/5/661.short The Children of Atomic Bomb Survivors: A Genetic Study. 1992. No differences were found (in frequencies of birth defects, stillbirths, etc), thus allaying the immediate public concern that atomic radiation might spawn an epidemic of malformed children.
  17. ^ Teratology in the Twentieth Century Plus Ten
  18. ^ http://www.nature.com/bjc/journal/v88/n3/full/6600748a.html
  19. ^ http://www.rerf.jp/radefx/genetics_e/birthdef.html (RERF)Radiation Effects Research Foundation. Formerly known as the (ABCC)Atomic Bomb Casualty Commission.
  20. ^ http://www.eenews.net/public/Greenwire/2011/04/11/1
  21. ^ "WHO Disease and injury country estimates". World Health Organization. 2009. Retrieved Nov 11, 2009. 
  22. ^ Lozano, R (Dec 15, 2012). "Global and regional mortality from 235 causes of death for 20 age groups in 1990 and 2010: a systematic analysis for the Global Burden of Disease Study 2010.". Lancet 380 (9859): 2095–128. doi:10.1016/S0140-6736(12)61728-0. PMID 23245604. 
  23. ^ Gittelsohn A., Milham S. (1964) Statistical study of twins—methods. Am. J. Public Health Nations Health 54 p. 286–294.
  24. ^ Fernando J., Arena P., Smith D. W. (1978) Sex liability to single structural defects. Am. J. Dis. Child 132 p. 970 –972.
  25. ^ Lubinsky M. S. (1997) Classifying sex biased congenital anomalies. Am. J. Med. Genet. 69 p. 225–228.
  26. ^ Lary J. M., Paulozzi L. J. (2001) Sex differences in the prevalence of human birth defects: a population-based study. Teratology 64 p. 237–251.
  27. ^ a b c d e f Wei Cui, Chang-Xing Ma, Yiwei Tang, e. a. (2005) Sex Differences in Birth Defects: A Study of Opposite-Sex Twins. Birth Defects Research (Part A) 73 p. 876–880.
  28. ^ a b World Health Organization reports). "Congenital malformations", Geneve, 1966, p. 128.
  29. ^ Darwin C. (1871) The descent of man and selection in relation to sex. London, John Murray, 1st ed.
  30. ^ Kumar, Abbas and Fausto, eds., Robbins and Cotran's Pathologic Basis of Disease, 7th edition, p.470.
  31. ^ Dicke JM (1989). "Teratology: principles and practice". Med. Clin. North Am. 73 (3): 567–82. PMID 2468064. 
  32. ^ a b c d e f g h i j k l m n o p q r Rajewski P. M., Sherman A. L. (1976) The importance of gender in the epidemiology of malignant tumors (systemic-evolutionary approach). In: Mathematical treatment of medical-biological information. M., Nauka, p. 170–181.
  33. ^ a b c d Montagu A. (1968) Natural Superiority of Women, The, Altamira Press, 1999.
  34. ^ a b c d e f g h i Riley M., Halliday J. (2002) Birth Defects in Victoria 1999-2000, Melbourne.
  35. ^ Shaw G.M., Carmichael S.L., Kaidarova Z., Harris J.A. (2003) Differential risks to males and females for congenital malformations among 2.5 million California births, 1989-1997. Birth Defects Res. A Clin. Mol. Teratol. 67(12) p. 953-958.
  36. ^ Reyes F.I., Boroditsky R.S., Winter J.S., Faiman C. (1974) Studies on human sexual development. II. Fetal and maternal serum gonadotropin and sex steroid concentrations. J. Clin. Endocrinol. Metab. 38 p. 612– 617.

External links[edit]