Monosomy disorders occur during the development of the fetus and are characterized by a partial or complete pair of a chromosome missing. While these disorders are relatively rare, the most common are Turner syndrome and Cri du chat syndrome. Other disorders, such as 1p36 deletion syndrome and Alfie syndrome, are extremely rare. Turner syndrome is the only complete monosomy that is compatible with life; any other type is fatal in utero or directly after birth. Those who live with a monosomy disorder other than Turner syndrome have partial monosomy, meaning only part of one side of the chromosome is missing.
Turner syndrome affects approximately one in 2,500 women. The chromosome pair that determines female sex, known as XX, is missing one of the Xs in Turner syndrome. Without treatment, women with this monosomy disorder will only grow to less than 5 feet (1.5 meters) and will not go through puberty. With the early use of growth hormones and estrogen replacement, these problems can be avoided, although patients will always be infertile.
Turner syndrome can also cause some learning delays, especially in math, and can cause some physical abnormalities, such as a webbed neck, droopy eyelids, and excessive moles. With early treatment and therapy, people with Turner syndrome can usually attend classes with their atypical peers and live independently. In some cases, an egg donor along with IVF treatment can help them carry and deliver a child naturally.
Cri du chat syndrome, which means "crying cat" in French, is a monosomy disorder related to a missing part of chromosome 5. Along with various learning and physical disabilities, this disorder causes the larynx to develop abnormally. abnormal, resulting in a distinctive cry under 2 years of age. Physically, people with cri du chat often have a smaller than normal head, a round face, and very wide eyes. They also often have heart defects, poor muscle tone, and difficulty functioning in social settings, and they often display highly aggressive or unpredictable behavior. While there is no medical treatment available for this disorder, therapeutic treatments can often help patients with intellectual and social disabilities.
1p36 deletion syndrome, that is, a missing part of chromosome 1, can cause various physical and mental disabilities, including facial deformities and severe learning delays. This monosomy disorder is much rarer than Turner syndrome or Cri du chat; Therapy for delays in learning and social interaction are the only treatments available. Alfie syndrome, a missing part of chromosome 9, has fewer than 100 reported cases in the world, making it the rarest monosomy disorder.
The health problems as well as the facial and mental abnormalities present with Alfie syndrome are serious, although some cases have been found in which the patient's intellectual disability improved dramatically after therapy. In one case, a child went from having a profound intellectual disability, an IQ score of less than 20, to less than average on the IQ scale, meaning more than 70 points. In the absence of serious health problems, such as heart defects, people with these disorders typically have long lifespans, typically in their 50s and 70s. Due to the fact that many different parts of a chromosome can be missing, the severity of these disorders varies greatly from patient to patient.