NIH Rare Diseases :
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The following summary is from Orphanet , a European reference portal for information on rare diseases and orphan drugs. Orpha Number: 261494 Definition Kleefstra syndrome (KS) is a genetic disorder characterized by intellectual disability , childhood hypotonia , severe expressive speech delay and a distinctive facial appearance with a spectrum of additional clinical features. Epidemiology The prevalence is unknown. To date, 114 cases have been described. Clinical description Patients with KS have a distinctive facial appearance comprised of brachy-microcephaly , midface hypoplasia, unusual eyebrow shape, synophyrs, cupid bow upper lip, full everted lower lip, protruding tongue and prognathism. With age, facial features become coarser and dental anomalies, like retention of primary dentition, are seen. Birth weight is normal but half of children go on to suffer from obesity. Childhood hypotonia causes motor delay but most children walk independently by age 2 or 3. Most patients have moderate to severe intellectual disability with expressive speech delay and little speech development (nonverbal communication is possible). Additional features include congenital heart malformations (interauricular communication, ventricular septal defects, bicuspid aortic valve, pulmonary valve stenosis (see these terms)), genital defects in males (hypospadias, cryptorchidism, micropenis), renal defects (hydronephrosis, chronic renal insufficiency, renal cysts, vesico-ureteral reflux), epilepsy , recurrent infections, severe constipation and hearing problems. In adolescence/adulthood behavioral problems (aggressive/emotional outbursts, attention deficit problems, self-mutilation and severe sleep disturbances) can begin. Autistic-like behavior can be noted earlier in some children. Recurrent pulmonary infections, overweight and behavioral problems seem to be reported more often in those with KS due to a point mutation , whereas microcephaly, short stature , respiratory complications and tracheomalacia are more frequently seen in those with KS due to a 9q34 microdeletion. Etiology KS is caused by either a point mutation in the euchromatic histone -lysine N-methyltransferase 1 (EHMT1 ) gene (rarely) or by a microdeletion in the chromosome region 9q34.3 (seen in >85% of cases), leading to the loss of the entire gene. This gene encodes an enzyme that modifies histone function and is essential for normal development. Larger deletions (>1mb) are associated with more severe symptoms. Diagnostic methods Diagnosis of KS is determined by the presence of the characteristic clinical features and molecular genetic testing . A microarray detects any duplications/deletions. Fluorescent in situ hybridization (FISH) or multiplex ligation-dependent probe amplification (MLPA) can then be used to detect the specific 9q34.3 deletion seen in KS. Sequencing of the entire coding region of the EHMT1 gene can detect sequence variants. Differential diagnosis Differential diagnoses include Down, Pitt-Hopkins, Smith-Magenis, Rett and 2q23.1 microdeletion syndromes (see these terms). Antenatal diagnosis Antenatal diagnosis is offered to unaffected parents of a child with KS as they have a higher risk of having another child with this disorder. Genetic counseling Most reported cases have been de novo but familial recurrence has been seen. KS has a theoretical autosomal dominant transmission, but the majority of patients do not reproduce. Management and treatment Treatment requires a multidisciplinary team, specializing in patients with intellectual deficiencies. Special education and vocational training along with speech therapy, physical and occupational therapy and sensory integration therapy are recommended from an early age. Standard treatment is necessary for those with renal, cardiac and urologic issues and for hearing loss . Psychiatric care along with behavioral intervention therapy may be needed. Cardiac screening (for the presence of arrhythmias) as well as intestinal and renal/urologic monitoring is recommended. Medical follow-up is life-long. Prognosis The prognosis of KS is variable but in most cases it is not a life-threatening disease. Visit the Orphanet disease page for more resources.
MalaCards based summary :
Kleefstra Syndrome, also known as
chromosome 9q deletion syndrome, is related to
kleefstra syndrome due to a point mutation and
kleefstra syndrome 1, and has symptoms including
seizures An important gene associated with Kleefstra Syndrome is
EHMT1 (Euchromatic Histone Lysine Methyltransferase 1), and among its related pathways/superpathways are
Lysine degradation and
PKMTs methylate histone lysines. Affiliated tissues include
heart,
tongue and
eye, and related phenotypes are
malar flattening and
hypertelorism
Disease Ontology :
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A syndrome that is characterized by developmental delay and intellectual disability, severely limited or absent speech, and weak muscle tone.
Genetics Home Reference :
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Kleefstra syndrome is a disorder that involves many parts of the body. Characteristic features of Kleefstra syndrome include developmental delay and intellectual disability, severely limited or absent speech, and weak muscle tone (hypotonia). Affected individuals also have an unusually small head size (microcephaly) and a wide, short skull (brachycephaly). Distinctive facial features include eyebrows that grow together in the middle (synophrys), widely spaced eyes (hypertelorism), a sunken appearance of the middle of the face (midface hypoplasia), nostrils that open to the front rather than downward (anteverted nares), a protruding jaw (prognathism), rolled out (everted) lips, and a large tongue (macroglossia). Affected individuals may have a high birth weight and childhood obesity.
People with Kleefstra syndrome may also have structural brain abnormalities, congenital heart defects, genitourinary abnormalities, seizures, and a tendency to develop severe respiratory infections. During childhood they may exhibit features of autism or related developmental disorders affecting communication and social interaction. In adolescence, they may develop a general loss of interest and enthusiasm (apathy) or unresponsiveness (catatonia).
KEGG :
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Kleefstra syndrome (KLEFS), also known as the 9q subtelomeric deletion syndrome is characterized by intellectual disability, childhood hypotonia, and distinctive facial features. About 75% of Kleefstra syndrome is caused by microdeletion of 9q34.3 and 25% by intragenic EHMT1 mutation. Recently, a few patients with loss of function mutations affecting the histone methyltransferase KMT2C were reported.
