9q34 deletion syndrome  is a rare genetic disorder. Terminal deletions of chromosome 9q34 have been associated with childhood hypotonia, a distinctive facial appearance and developmental disability. The facial features typically described include arched eyebrows, small head circumference, midface hypoplasia, prominent jaw and a pouting lower lip. Individuals with this disease may often have speech impediments, such as speech delays. Other characteristics of this disease include: epilepsy, congenital and urogenital defects, microcephaly, corpulence, and psychiatric disorders. From analysis of chromosomal breakpoints, as well as gene sequencing in suggestive cases, Kleefstra and colleagues identified EHMT1 as the causative gene. This gene is responsible for producing the protein histone methyltransferase which functions to alter histones. Ultimately, histone methyltransferases are important in deactivating certain genes, needed for proper growth and development. Moreover, a frameshift, missense, or nonsense error in the coding sequence of EHMT1 can result in this condition in an individual. Signs and symptoms
Physical symptoms

Heart defects
Characteristics of autism
Genital defects (in males)
Childhood hypotonia
Respiratory infections
Motor delay
Renal defects
Severe delay or total lack of speech
Happy disposition
Dysmorphic facial featuresBehavioural symptoms

Passiveness
Sociability
Aggression
Biting or hitting
Moodiness
Disliking routine changes

Genetics
Despite the associated effects of Kleefstra, there is insubstantial information regarding to the lethality of Kleefstras. Most of the documented cases are de novo with the exception of one case due to hereditary factors; however, some cases may be a result of chromosomal translocations. In the exception case, the mother transferred the EHMT1 point mutation on to her child as she was a carrier of this gene defect. According to Mitter, et al.
The DNA samples (which are 25-80 base pairs in length) are then placed on slides to be observed under microscope. Lastly, EHMT1 sequencing is a process in which a single-strand of DNA from the EHMT1 gene is removed, and DNA polymerase is added in order to synthesize complementary strands. In turn, this allows scientists to map out a persons DNA sequence allowing for a diagnosis to be made. Treatment
Individual manifestations are treated by a multidisciplinary team. Epidemiology
Kleefstra syndrome affects males and females equally and approximately 75% of all documented cases are caused by Eu-HMTase1 disruptions while only 25% are caused by 9q34.3 deletions. There are no statistics on the effect the disease has on life expectancy due to the lack of information available. History
Kleefstra syndrome is a new condition that has only been known about for a few years and there have been fewer than 200 cases, reported. Due to the lack of cases worldwide, the history behind the origination is unclear. Research
A study published by the American Journal of Human Genetics performed an EHMT1 mutation analysis on 23 patients that showed symptoms of 9q34 deletion syndrome. The patients all varied in age. With respect to all the analyses, however, the clinical data focused on five patients, the majority being children. The first patient developed epilepsy early on in childhood, and had speech problems past age 8. He had hypoplasia and had prominent facial features, such as lips and mouth.