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.
Orbital floor fractures may trap the orbital tissue in such a way as to simulate Browns syndrome. Intermittent forms of vertical retraction syndrome have been associated with click, which occurs as the restriction is released (superior oblique click syndrome). Diagnosis
Diagnosis of Browns syndrome usually happens during a routine ophthalmologic appointment. Treatments
If binocular vision is present and head position is correct, treatment is not obligatory. Treatment is required for: visual symptoms, strabismus, or incorrect head position.Acquired cases that have active inflammation of the superior oblique tendon may benefit from local corticosteroid injections in the region of the trochlea. The goal of surgery is to restore free ocular rotations. Various surgical techniques have been used:
Harold Brown advocated that the superior oblique tendon be stripped. A procedure named sheathotomy. The results of such a procedure are frequently unsatisfactory because of reformation of scar tissue. Tenotomy of the superior oblique tendon (with or without a tendon spacer) has also been advocated. This has the disadvantage that it frequently produces a superior oblique paresis. Weakening of the inferior oblique muscle of the affected eye may be needed to compensate for iatrogenic fourth nerve palsy.During surgery, a traction test is repeated until the eye rotations are free and the eye is anchored in an elevated adducted position for about two weeks after the surgery. This maneuver is intended to prevent the reformation of scar tissue in the same places. Normalization of head position may occur but restoration of full motility is seldom achieved. A second procedure may be required.