Trisomy 8

Trisomy 8
Chromosome 8
Classification and external resources
Specialty	medical genetics
ICD-10	Q92
ICD-9-CM	758
DiseasesDB	32656
MeSH	D014314

Trisomy 8, also known as Warkany syndrome 2,^[1] is a human chromosomal disorder caused by having three copies (trisomy) of chromosome 8. It can appear with or without mosaicism.

Characteristics

Complete trisomy 8 causes severe effects on the developing fetus and can be a cause of miscarriage.^[2] Complete trisomy 8 is usually an early 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.^[3][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 retarded psychomotor development, moderate to severe mental retardation, 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 location and proportion of trisomy 8 cells compared to normal cells.

Other conditions

Trisomy 8 mosaicism affects wide areas of chromosome 8 containing many genes, and can thus be associated with a range of symptoms.

• Mosaic trisomy 8 has been reported in rare cases of Rothmund-Thomson syndrome, a genetic disorder associated with the DNA helicase RECQL4 on chromosome 8q24.3. The syndrome is "characterized by skin atrophy, telangiectasia, hyper- and hypopigmentation, congenital skeletal abnormalities, short stature, premature aging, and increased risk of malignant disease".^[7]
• 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]
• Trisomy and other rearrangements of chromosome 8 have also been found in tricho–rhino–phalangeal syndrome.^[9]
• 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]
• Trisomy is also found in some cases of chronic myeloid leukaemia, potentially as a result of karyotypic instability caused by the bcr:abl fusion gene.

References

1. DDB 32656
2. Riccardi VM (1977). "Trisomy 8: an international study of 70 patients". Birth Defects Orig. Artic. Ser. 13 (3C): 171–84. PMID 890109.
3. Jones, K. L. (2005). Smith's Recognizable Patterns of Human Malformation. (6th ed.). Philadelphia: W. B. Sanders Company.
4. Jones, K. L. (2005). Smith's Recognizable Patterns of Human Malformation. (6th ed.). Philadelphia: W. B. Sanders Company.
5. Riccardi VM (1977). "Trisomy 8: an international study of 70 patients". Birth Defects Orig. Artic. Ser. 13 (3C): 171–84. PMID 890109.
6. Lai CC (1975). "Trisomy 8 syndrome". Clin. Orthop. Relat. Res. 110: 238–43. PMID 1157389.
7. "MIM ID #268400 ROTHMUND-THOMSON SYNDROME; RTS". NCBI/OMIM.
8. "MIM ID *134450 FACTOR VII REGULATOR; F7R". NCBI/OMIM.
9. "MIM ID #190350 TRICHORHINOPHALANGEAL SYNDROME, TYPE I; TRPS1". NCBI/OMIM.
10. "MIM ID #179613 RECOMBINANT CHROMOSOME 8 SYNDROME". NCBI/OMIM.

External links

• U.S. National Library of Medicine: Warkany Syndrome 2