Monosomy, with the presence of only one
chromosome (instead of the typical two in humans) from a pair, which affects chromosome 14. Fetuses with monosomy 14 are not viable. Only
mosaic
A mosaic () is a pattern or image made of small regular or irregular pieces of colored stone, glass or ceramic, held in place by plaster/Mortar (masonry), mortar, and covering a surface. Mosaics are often used as floor and wall decoration, and ...
cases exist and these usually present with severe symptoms such as
intellectual disability
Intellectual disability (ID), also known as general learning disability (in the United Kingdom), and formerly mental retardation (in the United States), Rosa's Law, Pub. L. 111-256124 Stat. 2643(2010).Archive is a generalized neurodevelopmental ...
,
ocular colobomata,
microcephaly
Microcephaly (from Neo-Latin ''microcephalia'', from Ancient Greek μικρός ''mikrós'' "small" and κεφαλή ''kephalé'' "head") is a medical condition involving a smaller-than-normal head. Microcephaly may be present at birth or it m ...
, and
seizures
A seizure is a sudden, brief disruption of brain activity caused by abnormal, excessive, or synchronous neuronal firing. Depending on the regions of the brain involved, seizures can lead to changes in movement, sensation, behavior, awareness, o ...
. Organ malformations are also associated due to the chromosome 14 having several genes for organ development, including heart defects, and brain problems. In full monosomy 14 in all cells, the total number of chromosomes is 45 instead of 46. Many are stillborn if the pregnancy does progress to term. The prognosis is generally poor and the symptoms include intellectual disability, small head, ocular problems, seizures, and heart malformations. Monosomy 14 is not the only lethal monosomy, as several other monosomies (with the exception of
Turner syndrome
Turner syndrome (TS), commonly known as 45,X, or 45,X0,Also written as 45,XO. is a chromosomal disorder in which cells of females have only one X chromosome instead of two, or are partially missing an X chromosome (sex chromosome monosomy) lea ...
) are lethal. They may have kidney issues, ventricular underdevelopment, or brain defects. Their eyes, heart, brain, and head are far less developed than fetuses with two copies of chromosome 14. The severe gene dosage imbalance is common in these fetuses. Some signs include
**
Intellectual disabilities
Intellectual disability (ID), also known as general learning disability (in the United Kingdom), and formerly mental retardation (in the United States), Rosa's Law, Pub. L. 111-256124 Stat. 2643(2010).Archive is a generalized neurodevelopmental ...
**
Coloboma
A coloboma (from the Greek , meaning "defect") is a hole in one of the structures of the eye, such as the iris, retina, choroid, or optic disc. The hole is present from birth and can be caused when a gap called the choroid fissure, which is ...
** Stunted growth
**A small head with ocular problems
**
Microcephaly
Microcephaly (from Neo-Latin ''microcephalia'', from Ancient Greek μικρός ''mikrós'' "small" and κεφαλή ''kephalé'' "head") is a medical condition involving a smaller-than-normal head. Microcephaly may be present at birth or it m ...
**
Neural tube defects
Neural tube defects (NTDs) are a group of birth defects in which an opening in the spine or cranium remains from early in human development. In the third week of pregnancy called gastrulation, specialized cells on the dorsal side of the embry ...
**
Heart defect
A congenital heart defect (CHD), also known as a congenital heart anomaly, congenital cardiovascular malformation, and congenital heart disease, is a defect in the structure of the heart or great vessels that is present at birth. A congenital h ...
References
External links
Autosomal monosomies and deletions
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