Symptoms and signs
Recognised symptoms are:
Only one set of genes on the two chromosomes function (haploinsufficiency)
Thrombocytopenia-absent radius (TAR syndrome), in case of a class II-deletion
Neurological-psychiatric problems: schizophrenia; epilepsy; learning problems; cognitive disabilities — mild to moderate; developmental delay — mild to moderate (milestones like sitting, standing and walking; come at a later period in childhood); children show an ataxic gait and fall down a lot
Dysmorphism: slightly unusual facial appearance; disturbed growth; skeletal malformations; small head (microcephaly); prominent forehead; bulbous nose; deep-set eyes; broad thumbs; broad toes; squint; very flexible joints; clavicular pseudoarthrosis (the collarbone doesnt develop normally) (class II-deletion); an extra transverse crease of the fifth finger (class II-deletion)); problems with the development of the vagina (Müllerian aplasia)
Eyes: cataracts
Heart abnormalities and cardiovascular anomalies (30% of the cases): anomalous origin of the coronary artery (Class II-deletion)
Kidneys: missing kidney or floating kidneys
Cancer: neuroblastoma
Sleep disturbancesIt is not clear whether the list of symptoms is complete. Very little information is known about the syndrome. The syndrome can have completely different effects on members of the same family.A common deletion is between 1.0–1.9Mb. Mefford states that the standard for a deletion is 1.35Mb. The largest deletion seen on a living human is over 5 Mb. Cause
Meiosis is the process of dividing cells in humans. In meiosis, the chromosome pairs split and a representative of each pair goes to one daughter cell. In this way the number of chromosomes will be halved in each cell, while all the parts on the chromosome (genes) remain, after being randomized.
1q21.1 deletion syndrome is a rare aberration of chromosome 1. A human cell has one pair of identical chromosomes on chromosome 1. With the 1q21.1 deletion syndrome, one chromosome of the pair is not complete, because a part of the sequence of the chromosome is missing. One chromosome has the normal length and the other is too short. In 1q21.1, the 1 stands for chromosome 1, the q stands for the long arm of the chromosome and 21.1 stands for the part of the long arm in which the deletion is situated. The syndrome is a form of the 1q21.1 copy number variations, and it is a deletion in the distal area of the 1q21.1 part. The CNV leads to a very variable phenotype, and the manifestations in individuals are quite variable. Some people who have the syndrome can function in a normal way, while others have symptoms of intellectual impairment and various physical anomalies.1q21.1 microdeletion is a very rare chromosomal condition. Only 46 individuals with this deletion have been reported in medical literature as of August 2011.