Complete trisomy 8 causes severe abnormalities in the developing fetus and can be a cause of miscarriage.[2][3]
Complete trisomy 8 is usually a gestational lethal condition, whereas trisomy 8 mosaicism is less severe and individuals with a low proportion of affected cells may exhibit a comparatively mild range of physical abnormalities and developmental delay.[4] Individuals with trisomy 8 mosaicism are more likely to survive into childhood and adulthood and exhibit a characteristic and recognizable pattern of developmental abnormalities. Common findings include stunted psychomotor development, moderate to severe intellectual disability, variable growth patterns which can result in either abnormally short or tall stature, an expressionless face, and many musculoskeletal, visceral, and eye abnormalities, as well as other anomalies.[5] A deep plantar furrow is considered to be pathognomonic of this condition, especially when seen in combination with other associated features.[6] The type and severity of symptoms are dependent upon the prevalence of the affected cells and their location within the body.[citation needed]
Other conditions
Trisomy 8 mosaicism affects wide areas of chromosome 8, containing many genes, and can thus be associated with several symptoms.
Some individuals trisomic for chromosome 8 were deficient in production of coagulation factor VII due to a factor 7 regulation gene (F7R) mapped to 8p23.3-p23.1.[8]
Small regions of chromosome 8 trisomy and monosomy are also created by recombinant chromosome 8 syndrome (San Luis Valley syndrome), causing anomalies associated with tetralogy of Fallot, which results from recombination between a typical chromosome 8 and one carrying a parental paracentric inversion.[10]
The simplest and easiest way to detect trisomy 8 is by a karyotype, a photograph representing all chromosomes of a cell in an orderly manner. Amniocentesis is also a technique for diagnosis. Samples from the amniotic fluid are taken from a fetus, cultured, then analyzed by a karyotype. If the photograph shows 3 copies of chromosome 8 instead of 2, then the individual has trisomy 8.
