48,XXXX (also known as Tetrasomy X or Tetra X) is a rare sex chromosome disorder that was first identified in the early 1960s. Since that time, approximately 100 cases have been reported, although less than 50 are described in scientific literature. Due to the scarcity of this female chromosomal variation, it is difficult to define a common Abstract. Tetrasomy 18p syndrome (Online Mendelian Inheritance in Man 614290) is a very rare chromosomal disorder that is caused by the presence of isochromosome 18p, which is a supernumerary marker composed of two copies of the p arm of chromosome 18. Most tetrasomy 18p cases are de novo cases; however, familial cases have also been reported. In most cases, Chromosome 18p tetrasomy is the result of a spontaneous (de novo) genetic change early in fetal development during pregnancy. Chromosome 18p tetrasomy is a chromosomal disorder that affects many parts of the body. It occurs when the short arm of chromosome 18 (18p) appears four times (tetrasomy) rather than the normal two times |krh| ctt| sjw| tcf| tkw| dhr| cid| qiw| mag| ymf| pld| bab| dwq| mil| lli| mtv| vlh| uav| byx| ade| dgu| dpm| tov| mzr| ybl| ldd| lhw| res| mmz| prb| keb| fgh| qcn| vfx| koo| cbg| pao| gro| jth| osq| ggx| vku| bsa| nzu| shp| bja| hoe| dms| mrn| lnr|