What is Trisomy 13 — Patau syndrome ?

Tri­somy 13 is also known as patau syn­drome. it is a genet­ic con­di­tion aris­ing due to pres­ence of an extra copy of chro­mo­some 13. The man­i­fes­ta­tion of this con­di­tion include Car­diac anom­alies Defect in ner­vous sys­tem Hypo­to­nia or weak­er Mus­cle Tone Defor­mi­ties in phys­i­cal fea­ture and Intel­lec­tu­al abilities.

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The sur­vival rate of such affect­ed indi­vid­ual is very low due to mul­ti­ple seri­ous abnor­mal­i­ty is and effect and most chil­dren fail to live beyond few weeks or months. The occur­rence of tri­somy 13 is just one in about 16000 cas­es and the chances increas­es fair­ly with the mater­nal age. The extra genet­ic mate­r­i­al may be present in form of a com­plete chro­mo­some 13 that is 3 copies of chro­mo­some 13 at present. In such cas­es the sim­i­lar­i­ty of anom­alies is high, low­er­ing the chances of sur­vival of affect­ed individual.

In mosa­ic con­di­tion and extra copy of chro­mo­some 13 is present only in few cells of the body and not all there­fore its effect are less severe. 

If the extra genet­ic mate­r­i­al chro­mo­some 13 gets translo­cat­ed to anoth­er chro­mo­some, it is called translo­ca­tion tri­somy 13.This usu­al­ly hap­pens dur­ing gamete for­ma­tion or some­time dur­ing the ear­ly stages of embryo development.Translocation tri­somy 13 is inher­i­ta­ble a par­ent with a bal­anced translo­ca­tion is a poten­tial career and is like­ly to pro­duce a child with tri­somy 13.

In 1966 class patau and his Asso­ciates observed and Infant with cross devel­op­men­tal mal­for­ma­tion with the kary­otype of 47 chromosomes.

The addi­tion­al chro­mo­some was medi­um-sized, one of acro­cen­tric D group.The G and Q Band­ing tech­niques have iden­ti­fy the extra D chro­mo­somes as num­ber 13.

The tri­somy 13 con­di­tion has since been described in many new­borns and is called Patau syndrome,Being des­ig­nat­ed as 47,13 +.

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70% of the tri­somy 13 cas­es are caused by mei­ot­ic nondis­junc­tion ;10% of the cas­es are tri­som­ic mosaics; and 20 % are par­tial­ly tri­som­ic due ti translocation. 

As a chro­mo­some 13 con­tains con­sid­er­able active genet­ic mate­r­i­al most chro­mo­some 13 tri­somies abort.Of those that are life born 90% die dur­ing the first year of life.Those few that sur­vived beyond the age of 2 years of a from severe men­tal retardation.

The characteristics of trisomy 13 include

• Seizures
• Mod­er­ate Micro­cephaly ( small head )
• Wide space Eyes
• Beaked nose
• Cleft of the lips and palate
• low set ears 
• Scalp defects
• And Char­ac­ter­is­tic ‘trig­ger thumb’ (the thumb and index fin­gers over­lap the third finger).

Tri­somy 13 baby dis­play simi­an crease (one con­tin­u­ous crease across the palm of the hand ),as in down syn­drome, As well as poly­dacty­ly (extra fin­gers and toes) ‚con­gen­i­tal heart dis­ease, kid­ney dis­or­ders and mal­formed genitalia.

The aver­age mater­nal and pater­nal ages of par­ents of affect­ed infants are high­er than the ages of par­ents of nor­mal chil­dren , But pater­nal ages are not as high as the aver­age mater­nal age as in case of down syndrome.

Both male and female par­ent have aver­age about 32 years of age when the affect­ed child is born. because the con­di­tion is so rare, it is not known as the ori­gin of the extra chro­mo­some is more of a mater­nal and pater­nal aris­es equal­ly from oth­er parents.