17q12 Deletion Syndrome

Genetics

17q12 deletion syndrome is caused by a missing piece of chromosome 17 (microdeletion) that is present from the moment the child is conceived. There are many different microdeletions that can occur on chromosome 17, but 17q12 deletion syndrome is caused by a deletion of a specific ~1.4Mb region on the long arm (“q arm”) of chromosome 17 at position 12 (one-two). The most common test used to identify the deletion is called a chromosomal microarray (CMA). The deletion is too small to be detected with a karyotype. Based on current research, about 1 in 14,500 people in the general population have the deletion syndrome. It is more common in populations with developmental disorders (developmental delay, autism, intellectual disability) and schizophrenia. It is most common in individuals with kidney/urinary tract abnormalities.

Inheritance

The deletion is most often a brand new (de novo), sporadic event in the child that is diagnosed. About 30% of the time, or 3 in 10 people with the deletion will have inherited it from a parent. In these cases, there is a 50% chance (1 in 2) that each of that parent’s children will also have the deletion. If it was de novo (both parents tested negative), then the chances that a sibling has it is lower than 1%.

Clinical Features

A syndrome is defined as a recognizable group of signs and symptoms that consistently occur together. The common features that characterize the deletion syndrome can be grouped into three categories: kidney and urinary tract abnormalities, maturity onset diabetes of the young type 5 (MODY-5), and neurodevelopmental and psychiatric disorders. It is important to remember that no two people with the deletion will have the same combination and/or severity of symptoms, even people within the same family.

Kidneys: echogenic kidneys on prenatal ultrasound, single kidney, underdeveloped kidneys, kidney cysts, reduced ability to concentrate the urine (tubulointerstitial disease)
Urinary Tract: absent or underdeveloped cervix, vagina and/or uterus, bicornuate uterus in females and undescended testes in males
MODY-5
Neurodevelopmental/Psychiatric: developmental delay, autism, learning disability, intellectual disability, anxiety, bipolar disorder, schizophrenia, etc.

Some features have been reported less commonly including:

Heart defects
Macrocephaly (large head size)
Seizures
Elevated liver enzymes
Eye/Vision problems: strabismus (crossed eye), nystagmus (shaky eye), cataracts
Short stature