15q24 Microdeletion Syndrome

What is 15q24 microdeletion syndrome?

15q24 microdeletion syndrome occurs when a small piece of a chromosome is deleted in a person’s cells. Human traits are inherited from a person’s father and mother; each one contributes a copy of a gene, which interacts with the other copy. Genes are located in chromosomes, which carry the genetic characteristics of individuals and are located in the nucleus of all body cells. Humans have 23 pairs of chromosomes. In the case of 15q24 microdeletion syndrome, the deletion occurs on chromosome 15. The deletion leads to the symptoms detailed below.

15q24 microdeletion syndrome is very rare; only a few dozen patients have been identified.

What are the symptoms of 15q24 microdeletion syndrome?

Mild to moderate intellectual disability
Delayed speech development
Weak muscle tone
Short stature
Loose joints
Distinct facial features: widely set eyes, downward-pointing outer corners of the eyes, broad eyebrows, high front hairline, broad nasal bridge, long space between the upper lip and nose, and a full lower lip
Squinting vision
Hearing loss
Genital abnormalities in males, such as unusually small penis and opening of the urethra on the underside of the penis

What causes 15q24 microdeletion syndrome?

Patients with 15q24 microdeletion syndrome are missing somewhere between 1.7 million and 6.1 million DNA building blocks. Each chromosome has a short arm designated “p” and a long arm designated “q,” and then is divided even more into numbered bands. In this instance, the deletion occurs on the long arm of chromosome 15 (more specifically, at a position called q24). This region contains many genes that are thought to be crucial for normal development. The loss of these genes is likely the cause of symptoms.

The identified cases so far are a result of spontaneous deletions, meaning that they have occurred in people with no family history of the disorder. Researchers believe that the chromosomal change likely occurs as a random event during reproduction or in early fetal development.