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Klinefelter Syndrome - Definition, Description, Causes and symptoms, Diagnosis, Treatment, Prognosis chromosomes males male chromosome Klinefelter syndrome is a chromosome disorder in males. People with this condition are born with at least one extra X chromosome. Description Klinefelter syndrome is a condition where one or more extra X-chromosomes are present in a male. Boys with this condition appear normal at birth. They enter puberty normally, but by mid puberty have low levels of testosterone causing small testicles and the inability to make sperm. Affected males may also have learning disabilities and behavior problems such as shyness and immaturity and an increased risk for certain other health problems. Klinefelter syndrome is one of the most common chromosomal abnormalities. About 1 in every 500 to 800 males is born with this disorder. Approximately 3% of the infertile male population have Klinefelter syndrome. Causes and symptoms Chromosomes are found in the cells in the body. Chromosomes contain genes, structures that tell the body how to grow and develop. Chromosomes are responsible for passing on hereditary traits from parents to child. Chromosomes also determine whether the child will be male or female. Normally, a person has a total of 46 chromosomes in each cell, two of which are responsible for determining that individual's sex. These two sex chromosomes are called X and Y. The combination of these two types of chromosomes determines the sex of a child. Females have two X chromosomes (the XX combination); males have one X and one Y chromosome (the XY combination). In Klinefelter syndrome, a problem very early in development results in an abnormal number of chromosomes. Most commonly, a male with Klinefelter syndrome will be born with 47 chromosomes in each cell, rather than the normal number of 46. The extra chromosome is an X chromosome. This means that rather than having the normal XY combination, the male has an XXY combination. Because people with Klinefelter syndrome have a Y chromosome, they are all male. Approximately 1/3 of all males with Klinefelter syndrome have other chromosome changes involving an extra X chromosome. Mosaic Klinefelter syndrome occurs when some of the cells in the body have an extra X chromosome and the other have normal male chromo somes. These males can have the same or milder symptoms than non-mosaic Klinefelter syndrome. Males with more than one additional extra X chromosome, such as 48,XXXY, are usually more severely affected than males with 47,XXY. Klinefelter syndrome is not considered an inherited condition. The risk of Klinefelter syndrome reoccurring in another pregnancy is not increased above the general population risk. The symptoms of Klinefelter syndrome are variable and not every affected person will have all of the features of the condition. Males with Klinefelter syndrome appear normal at birth and have normal male genitalia. From childhood, males with Klinefelter syndrome are taller than average with long limbs. Approximately 20–50% have a mild intention tremor, an uncontrolled shaking. Many males with Klinefelter syndrome have poor upper body strength and can be clumsy. Klinefelter syndrome does not cause homosexuality. Approximately 1/3 of males with Klinefelter syndrome have breast growth, some requiring breast reduction surgery. Most boys enter puberty normally, though some can be delayed. The Leydig cells in the testicles usually produce testosterone. With Klinefelter syndrome, the Leydig cells fail to work properly causing the testosterone production to slow. By mid-puberty, testosterone production is decreased to approximately half of normal. This can lead to decreased facial and pubic hair growth. The decreased testosterone also causes an increase in two other hormones, follicle stimulating hormone (FSH) and luteinizing hormone (LH). Normally, FSH and LH help the immature sperm cells grow and develop. In Klinefelter syndrome, there are few or no sperm cells. The increased amount of FSH and LH cause hyalinization and fibrosis, the growth of excess fibrous tissue, in the seminiferous tubules, where the sperm are normally located. As a result, the testicles appear smaller and firmer than normal. With rare exception, men with Klinefelter syndrome are infertile because they can not make sperm. While it was once believed that all boys with Klinefelter syndrome were mentally retarded, doctors now know that the disorder can exist without retardation. However, children with Klinefelter syndrome frequently have difficulty with language, including learning to speak, read, and write. Approximately 50% of males with Klinefelter syndrome are dyslexic. Some people with Klinefelter syndrome have difficulty with social skills and tend to be more shy, anxious, or immature than their peers. They can also have poor judgement and do not handle stressful situations well. As a result, they often do not feel comfortable in large social gatherings. Some people with Klinefelter syndrome can also have anxiety, nervousness and/or depression. The greater the number of X-chromosomes present, the greater the disability. Boys with several extra X-chromosomes have distinctive facial features, more severe retardation, deformities of bony structures, and even more disordered development of male features. Diagnosis Diagnosis of Klinefelter syndrome is made by examining chromosomes for evidence of more than one X chromosome present in a male. This can be done in pregnancy with prenatal testing such as a chorionic villus sampling or amniocentesis. Chorionic villus sampling is a procedure done early in pregnancy (approximately 10–12 weeks) to obtain a small sample of the placenta for testing. An amniocentesis is done further along in pregnancy (from approximately 16–18 weeks) to obtain a sample of fluid surrounding the baby for testing. Both procedures have a risk of miscarriage. Usually these procedures are done for a reason other than diagnosing Klinefelter syndrome. For example, a prenatal diagnostic procedure may be done on an older woman to determine if her baby has Down syndrome. If the diagnosis of Klinefelter syndrome is suspected in a young boy or adult male, chromosome testing can also be on a small blood or skin sample after birth. Treatment There is no treatment available to change chromosomal makeup. Children with Klinefelter syndrome may benefit from a speech therapist for speech problems or other educational intervention for learning disabilities. Testosterone injections started around the time of puberty may help to produce more normal development including more muscle mass, hair growth and increased sex drive. Testosterone supplementation will not increase testicular size, decrease breast growth or correct infertility. Prognosis While many men with Klinefelter syndrome go on to live normal lives, nearly 100% of these men will be sterile (unable to produce a child). However, a few men with Klinefelter syndrome have been reported who have fathered a child through the use of assisted fertility services. Males with Klinefelter syndrome have an increased risk of several conditions such as osteoporosis, autoimmune disorders such as lupus and arthritis, diabetes and both breast and germ cell tumors. Resources BOOKS Bock, R. Understanding Klinefelter's Syndrome: A Guide for XXY Males and Their Families. National Institutes of Health, USA, 1993. Probasco, Teri, and Gretchen A. Gibbs. Klinefelter Syndrome. Richmond, IN: Prinit Press, 1999. PERIODICALS Smyth, C.M., and W.J. Bremner. "Klinefelter Syndrome." Archives of Internal Medicine 158 (1998): 1309–1314. Smyth, Cynthia M. "Diagnosis and Treatment of Klinefelter Syndrome." Hospital Practice (September 15, 1999): 111–120 Staessen, C., et al. "Preimplantation Diagnosis for X and Y Normality in Embryos from Three Klinefelter Patients." Human Reproduction 11, no. 8. ORGANIZATIONS American Association for Klinefelter Syndrome Information and Support (AAKSIS) 2945 W. Farwell Ave., Chicago, IL 60645-2925. Klinefelter Syndrome and Associates, Inc. PO Box 119, Roseville, CA 95678-0119. ksinfo@genetic.org. Klinefelter's Organization. PO Box 60, Orpington, BR68ZQ. UK  . OTHER Klinefelter Syndrome Support Group Home Page. Carin Lea Beltz, M.S.
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Autor: Ljubica Šaran Matrix World Priroda je na jednostavan način uspjela riješiti problem razdvajanja dvije identične molekule DNK na suprotne polove za vrijeme mitoze i mejoze. Od ukupno 46 kromosoma u čovjeka 44 su autosomi, a preostala dva su heterokromosomi – spolni kromosomi ili gonosomi – koji određuju spol osobe: X i Y – kombinacija XX za ženski, a XY za muški spol. Većina od nas misli da su to kombinacije koje je priroda stvorila i da drugih kombinacija kromosoma nema, no to nije istina. Prije nego li nastavimo s čudima našeg tijela i razlikama između ljudi i spolova, koji su izgleda puno kompliciraniji nego li to možemo zamisliti pojasnit ću malo o čemu se zapravo radi kod XX i XY kromosoma. Za svaku vrstu broj kromosoma je specifičan, broj kromosoma koji možemo izbrojati kod zdravog ljudskog bića iznosi 46. Haploidne spolne stanice sadržavaju 22 autosoma i 1 heterokromosom (spermij X ili Y, a jajna stanica uvijek X). Kod ženskog spola (XX) spolni su kromosomi jednaki i sparuju se poput autosoma. Kod muškog spola (XY) spolni su kromosomi različiti i sparuju se tek malim dijelom na samim krajevima svojih kratkih krakova. Na Y-kromosomu taj se kraj nalazi uz sam SRY-gen, koji jedini determinira muški spol. Po svenu onome što smo učili u školama i što se piše po medijima, tu priča završava, ali u prirodi to uopće nije tako, naivno smo vjerovali kako postoje smo dvije kombinacije; XX i XY kombinacija koju već znaju i mala djeca. Aneuplodija je promjena broja kromosoma koja zahvaća pojedine kromosome u kromosomskom setu. Aneuploidni organizam može imati višak jednog ili više kromosoma ili manjak jednog ili više kromosoma. Kod Homo sapiensa aneuploidija zahvaća autosome i spolne kromosome. Klinefelterov sindrom – 47XXY Muškarci s Klinefelterovim sindromom imaju jedan suvišni X kromosom. Ta relatovno česta kromosomska nenormalnost javlja se jednom na svakih 700 novorođenih dječaka, pa ipak o tome jako malo znamo. Muškarac s Klinefelterovim sindromom. Tipično je da ovakvi muškarci narastu iznimno visoki no dlačice po tijelu i licu im budu gotovo nevidljive i čini se da ih ni ne trebaju brijati po licu, te imaju šire bokove. Većina ih ima problema u čitanju i govoru no rad s logopedom to može riješiti gotovo do neprimjetnosti. Ovakvi muškarci imaju slabije mišiće i slabiju koordinaciju. Za vrijeme puberteta odlike postanu još primjetnije jer ne proizvode dovoljno testosterona. Zbog toga često imaju problema s ginekomastijom – rastom grudi. 10% muškaraca s Klinefelterovim simptomom moraju kirurški smanjiti grudi. Kod njih je vrlo uobičajena sterilnost ili smanjena plodnost i često im testisi ostaju jako mali ili zakržljali. Ovaj poremečaj se zove i 47XXY jer u biti ovi muškarci imaju 47 kromosoma, a ne 46. Osim kod ljudi, ovakav se poremećaj može naći kod miševa i nekih drugih sisavaca. XXYY sindrom 48XXYY sindrom mogu imati samo muškarci. Ovakav poremećaj se događa među svakih 18000-40000 dječaka. Neki znanstvenici smatraju da je ovaj poremećaj varijacija Klinefelterovog sindroma jer muškarci s jednim i drugim poremećajem imaju iste fizičke odlike. No nedavna izučavanja su pokaza kako nije riječ o varijaciji Klinefelterovog sindroma. Varijacije kromosoma nisu samo XX i XY. Najveća je razlika što muškarci s XXYY sindromom imaju povećane mentalne probleme i nerazvijenost, hiperaktivnost, poremećaj pažnje, smanjenu mogućnost učenja, motoričke probleme, smanjenu mogućnost adaptacije, autizam, depresije, nervozu i drastične promjene raspoloženja. Ovo je jedan od najmanje izučavanih kromosomskih sindroma i nadamo se da ćemo u budućnosti imati više podataka o njemu. Sindrom 47XYY kromosoma Ovaj sindrom se pojavljuje otprilike na jednoj bebi u 1000 novorođenih dječaka. I ovdje je slučaj ponovno o dodatnom kromosomu, no kromosomu koji još više naglašava muške odlike. Dječaci s ovom sindromom rastu brže i više od ostalih vršnjaka, i na koncu narastu barem sedam centimetara viši od prosjeka, no osim visine bit će im izražene sve duge muške odlike, uključujući mišićavost, dlakavost i rast testisa. Oni često imaju izrazito velike ruke i stopala, no i česte su deformacije kostiju zbog izrazito visokog stasa. Kod ovakvih muškaraca se rano pojave akne kojih bude puno i smetaju ih godinama. No kod XYY muškaraca se primjećuje manji koeficijent inteligencije koji je oko u prosjeku manji za 11% od prosjeka vršnjaka. Polovica muškaraca s XYY kromosomom ima probleme s učenjem, lako dobivaju napade bijesa, agresivno se ponašaju, imaju probleme u razlučivanju što je dobro, a što loše, kao i druge kognitivne razlike, muškarci s XYY kromosomom često iskazuju antisocijalno i kriminalno ponašanje. XXX sindrom Jedna od 1000 djevojčica rađa se s viškom X kromosoma. Djevojčice s viškom X kromosoma u rijetkim slučajevima imaju niži kvocjent inteligencije od braće i sestara. Ponekad ovaj sindrom uzrokuje sterilnost, premda su neke žene s XXX kromosomom uspjele roditi zdravu djecu s normalnim brojem kromosoma. Neke žene imaju dodatni X kromosom samo u dijelu stanica, takav sindrom se naziva 46XX/47XXX mozaik. X kromosom. Problem s ovim sindromom je što su izučavani samo neki slučajevi, za razliku od XYY sindroma čiji se pripadnici lako mogu uočiti, XXX sindrom naočigled ne pokazuje svoju prisutnost u većini slučajeva. Posljednja istraživanja XXX sindroma su pokazala kako on ima izrazito blage efekte ako broj kromosoma X nije veći od četiri, točnije uočeni su slučajevi djevojčica s čak pet kromosoma X viška. Turnerov sindrom – X sindrom Ovaj sindrom se pojavljuje u djevojčica kada jedan ili oba X kromosoma u potpunosti nedostaju. Jedna od 2000 djevojčica se javi s ovakvim kromosomskim nedostatkom. Mnoge bebe s ovom sindromom imaju oticanje šaka i noga, a sa stražnje strane vrata imaju naboranu i mlohavu kožu. Djevojčica s Turnerovim sindromom prije i nakon operacije. Djevojčice i žene s Turnerovim sindromom imaju opne s obije strane vrata koje idu od ušiju do ramena i karakterizira ih niski rast. Često imaju preklopljene očne kapke, niske i velike uši, široki grudni koš s razmaknutim prsnim bradavicama i brojne tamne madeže po koži. Tipične otečene nožice djevojčica s Turnerovim sindromom. Također mogu imati slabo razvijene prste na rukama, a naročito na nogama. Osim ovoga imaju anomalije na spolovilu koje se ne razvija kao što se ne razvijaju ni unutrašnji spolni organi, i u jajnicima nemaju jajašaca pa stoga imaju i nedostatak pojave menstruacije, često razvijaju bubrežne probleme, abnormalne spletove krvnih žila, suženje aorte i povećan krvni pritisak. Žene s Turnerovim sindromom se loše snalaze u prostoru, matematika im predstavlja izrazit problem dok u verbalnim zadacima i testovima inteligencije postižu i nadprosječan uspjeh. Rijetko imaju mentalnih problema i nedostataka. Većina djece koja se začnu s Turnerovim sindromom dožive spontani pobačaj u 99% ili budu mrtvorođena. Za sada nije poznato zašto se događaju ovakve promjene, iako su neki znanstvenici pokušali povezati neobične varijacije spolnih kromosoma s problemima u plodnosti roditelja i dobivanju djece u starijim godinama ali za sada su takvi zaključci dovedeni na pojedinačnom ispitivanju, a ne na većem uzorku ispitanika. U prošlosti je veliki broj ovakvih poremećaja prolazio neopaženo, naročito zbog činjenice da je citogenetika i izučavanje kariotipa (kromosomskih kompleta u čovjeka) mlada znanost. Pitam se što li ćemo još otkriti o ljudima i porukama koje nose u kariotipima u budućnosti? Refernece: XYY Supermale Syndrome Symptoms Kategorije:TEHNOLOGIJA I ZNANOST, U ZDRAVOM TIJELU ZDRAV DUH