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Chromosome 1, 1p36 deletion syndrome is a medical condition caused by a rare chromosomal disorder where deletion of a portion of chromosome 1 causes various abnormalities such as heart defects, mental retardation, developmental delay, facial dysmorphism and short stature. The symptoms are variable depending on the exact location of chromosomal deletion.[1]
The first cases of 1p36 deletion syndrome were described in the 1980s. However, since many of these individuals also had other chromosomal imbalances, symptoms varied widely. The reason it took so long to recognize the condition as a distinct chromosome deletion syndrome is that the deletions causing the disorder are too small to be detected in a routine chromosomal analysis. FISH (fluorescent in situ hybridization) and DNA-based technology known as MPLA (multiple ligation probe amplification) used in testing have aided in diagnosing an increasing number of cases since the 1990s.[2]
1p36 Deletion Syndrome is a congenital genetic disorder caused by the deletion of the most distal light band of the short arm of chromosome 1. Chromosome 1 is the largest human chromosome and represents about 8 percent of the total DNA in human cells. The “p” stands for the short or ‘petite’ arm of the chromosome. ’36’ stands for the location of the deletion on the chromosome.
Notice the breakpoints in the picture of chromosome 1. The breakpoints for 1p36 Deletion Syndrome have been variable and have ranged from bands 1p36.13 to 1p36.33. Studies have suggested that the larger the deletion, the more severe the symptoms exhibited in the individual, but this has not been proven definitively.
Most deletions in chromosome 1p36 are new mutations, that occur before fertilization, during the formation of gametes (eggs or sperm). There have also been reports of patients with 1p36 deletion syndrome whose parents have a balanced or symmetrical translocation. This means a portion of one chromosome is transferred to another chromosome, so the parent has the “36” portion of chromosome 1 attached in an alternate location. When this occurs, cell division creates gametes that are missing a piece of 36.
In new mutations, the mechanism causing chromosome breakage is unknown. Deletions of paternal origin (father) are larger than the deletions deriving from the maternal (mother) chromosome. The majority of deletions are maternally derived. There do not seem to be differences in the clinical manifestations (the symptoms or observable conditions which are seen as a result of 1p36) based on whether the deletion is on the paternal or maternal chromosome.[3]
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