Cohen syndrome (COH1)

What is Cohen Syndrome?

Cohen syndrome is an inherited genetic condition and rare disease.

There are less than 1000 recorded cases of the syndrome to date, but as symptoms vary considerably between individuals, there may be many more unreported and undiagnosed cases.

This under diagnosis is due to the fact that the combination of some of the main symptoms- a very small head, truncal obesity and intellectual impairment- are also common to many other syndromes.

Syndrome Synonyms:
Chs1, Formerly Coh Hypotonia, Obesity, And Prominent Incisors Pepper Syndrome

What gene change causes Cohen Syndrome?

Mutations in the VPS13B gene, also sometimes known as the COH1 gene, are responsible for the disorder. The disease is inherited in an autosomal recessive pattern.

Autosomal recessive inheritance means an affected individual receives one copy of a mutated gene from each of their parents, giving them two copies of a mutated gene. Parents, who carry only one copy of the gene mutation will not generally show any symptoms, but have a 25% chance of passing the copies of the gene mutations onto each of their children.

what are the main symptoms of Cohen Syndrome?

The main symptoms of the syndrome include developmental delay and intellectual disability.

Physical and facial characteristics of the disorder include a small head, nearsightedness (myopia) that progressively gets worse, and a breakdown in the light sensitive tissue found at the back of the eyes.
Hypermobility is another major symptom.

Unique facial features include thick hair and eyebrows, long eyelashes, down slanting eyes, a large nasal tip, a smooth philtrum and large central, upper teeth.

Other health conditions associated with the syndrome include obesity beginning in adolescence, and low white blood cells.

Possible clinical traits/features:
Cognitive impairment, Growth hormone deficiency, Kyphosis, Visual impairment, Hypoplasia of the maxilla, Hypoplasia of the zygomatic bone, Short stature, Prominent nasal bridge, High, narrow palate, Genu valgum, Gingival overgrowth, Childhood-onset truncal obesity, Short metatarsal, Reduced number of teeth, Short metacarpal, Sandal gap, Prenatal movement abnormality, Ventricular septal defect, Thoracic scoliosis, Microcephaly, Short philtrum, Strabismus, Thick eyebrow, Cryptorchidism, Cubitus valgus, Small for gestational age, Downslanted palpebral fissures, Motor delay, Delayed puberty, Coarse hair, Clinodactyly of the 5th finger, Chorioretinal dystrophy, Feeding difficulties in infancy, Facial hypotonia, Finger syndactyly, Thick corpus callosum, Macrodontia, Macrodontia of permanent maxillary central incisor, Tapered finger, Long toe, Low anterior hairline, Lumbar hyperlordosis, Muscular hypotonia, Mitral valve prolapse, Neurological speech impairment, Myopia, Neutropenia, Narrow palm, Neonatal hypotonia, I

How does someone get tested for Cohen Syndrome?

The initial testing for Cohen syndrome can begin with facial analysis screening, through the FDNA Telehealth telegenetics platform, which can identify the key markers of the syndrome and outline the need for further testing. A consultation with a genetic counselor and then a geneticist will follow. 

Based on this clinical consultation with a geneticist, the different options for genetic testing will be shared and consent will be sought for further testing.   

Medical information on Cohen Syndrome

DISEASE OVERVIEW:
Cohen syndrome is an autosomal recessive disorder due to pathogenic variants in the VPS13B gene. It is characterized by characteristic facial features; failure to thrive in infancy and childhood; truncal obesity in the teen years; early-onset hypotonia and developmental delays; microcephaly developing during the first year of life; moderate to profound psychomotor retardation; progressive retinochoroidal dystrophy and high myopia; neutropenia with recurrent infections and aphthous ulcers; a cheerful disposition; and joint hypermobility.

CLINICAL DESCRIPTION (GENERAL):
Phenotypic features of Cohen syndrome among the more than 200 affected individuals reported to date are variable and include progressive retinochoroidal dystrophy and myopia, acquired microcephaly, developmental delay, hypotonia, joint laxity, characteristic facial features, truncal obesity, cheerful disposition, and neutropenia.

CLINICAL DESCRIPTION (BODY SYSTEMS):
Note: Certain statistics presented here are from National Cohen Syndrome Database (NCSD) in which approximately 50% of individuals are Old Order Amish; the diagnosis of Cohen syndrome has been confirmed by molecular genetic testing in the vast majority of individuals.
Ophthalmologic. Individuals with Cohen syndrome had a first ophthalmologic visit and were prescribed their first pair of glasses at an average age of 4.5 years. Defective dark adaptation/night blindness (nyctalopia) was typically noticed after age seven years. However, studies of younger individuals with Cohen syndrome demonstrate that abnormal retinal findings and ERG changes are present much earlier in life [Kivitie-Kallio et al 2000, Chandler et al 2002]. The studies further show that the two most prominent ophthalmologic findings, myopia and retinal dystrophy, markedly progress in severity over time with many individuals developing a bull’s eye maculopathy.
The progressive myopia and late-onset lens subluxation that occur in some individuals result from progressive laxity of zonules and progressive rounding up of the lens (spherophakia). Older individuals can have tremulousness of the iris (iridodonesis) because of lens subluxation and/or microspherophakia.
More than 70% of individuals in the NCSD fall often or trip easily, most likely because of constriction of peripheral visual fields secondary to retinal degeneration. Among ten individuals from nine families of Italian heritage with Cohen syndrome, 90% had retinal dystrophy and 80% had high myopia [Katzaki et al 2007]. Twenty percent of individuals in the Greek cohort developed blindness [Douzgou & Petersen 2011, Douzgou et al 2011], although progression to complete blindness has not been reported in other ethnic groups to the authors’ knowledge.
Other reported ophthalmic features include astigmatism, strabismus, microcornea, microphthalmia, sluggish pupillary reaction, iris atrophy and oval pupil, cataracts, optic atrophy, bull’s-eye maculopathy, coloboma of the retina or lids, congenital ptosis, and exophthalmos [Taban et al 2007]. Corneal changes and early-onset cataracts are frequently observed in individuals of Greek ancestry, but not in other ethnic groups [Douzgou & Petersen 2011, Douzgou et al 2011]. A few individuals have developed glaucoma and retinal detachments [Traboulsi, personal communication].

Microcephaly develops during the first year of life and continues into adulthood. Although 80% of mothers providing data to the NCSD reported that their infants had a small head size at birth, the average birth head circumference (35 cm) was in fact in the 50th centile. Earlier studies also reported normal head circumference at birth [Kivitie-Kallio & Norio 2001, Chandler et al 2003a, Hennies et al 2004].

Developmental. All children with Cohen syndrome have delayed developmental milestones in the first year of life. Analysis of individuals in the NCSD showed fairly consistent findings on certain developmental milestones compared with other cohorts with Cohen syndrome (Table 1) [Kivitie-Kallio & Norio 2001, Chandler et al 2003a, Nye et al 2005]. Overall, children with Cohen syndrome attain developmental milestones at a rate slower than average (Table 1), and once achieved, psychomotor skills do not regress. All but one of the individuals in the NCSD is able to walk without assistance, but at least 20% are unable to communicate verbally. The degree of developmental delay varies considerably, even among sibs [Horn et al 2000].

Table 1.
Timing of Achievement of Developmental Milestones in Cohen Syndrome
Finnish Cohort 1
Roll over: 4-12 months
Sit independently: 10-18 months
Walk independently: 2-5 years
Speak first words: 1-5 years
Speak in sentences: 5-6 years

English Cohort 2
Roll over: —
Sit independently: 12 months
Walk independently: 2.5 years
Speak first words: 2.5 years
Speak in sentences: 5 years

NCSD (US) Cohort 3
Roll over: 7 months
Sit independently: 11 months
Walk independently: 2.5 years
Speak first words: 3.2 years
Speak in sentences: 4.2 years
1. Kivitie-Kallio & Norio [2001]
2. Chandler et al [2003a]
3. Nye et al [2005]

Hypotonia. Half of mothers whose children are included in the NCSD recalled reduced fetal movement during an otherwise normal pregnancy. Infants with Cohen syndrome frequently have feeding and breathing difficulties during the first days of life, likely related to hypotonia. The majority of newborns with Cohen syndrome are hypotonic. Hypotonia is present in all infants by age one year [Kivitie-Kallio & Norio 2001] and appears to improve over time regardless of intervention. The mechanism of hypotonia is unknown but speculated to be of central nervous system origin [Kivitie-Kallio et al 1998].

Joint laxity and additional musculoskeletal features including kyphosis, scoliosis, and pes planovalgus are most likely the consequence of hypotonia. The relatively disease-specific motor clumsiness appears to be quite common [Kivitie-Kallio et al 2000, Chandler et al 2003a].

Distinctive facial features have been described in different ethnic populations. Features include hypotonic facies, thick hair, low hairline, high-arched and wave-shaped eyelids, long and thick eyelashes, thick eyebrows, prominent nasal root, high and narrow palate, smooth or short philtrum, and prominent upper central incisors; the latter two together result in an open-mouth appearance. Lack of the frontonasal angle, together with a short philtrum, made the nose appear “overly long” in a cohort from Greece [Bugiani et al 2008]. Horn et al [2000] and Falk et al [2004] also found that although quite consistent among affected individuals within a particular ethnic group, facial gestalt appears to be inconsistent across ethnic populations. However, taking into consideration that reported individuals with Cohen syndrome are evaluated by different clinicians, the distinctive facial features that are shared by individuals from different ethnic backgrounds are fairly impressive. In fact, a significant number of parents in the NCSD noted distinct facial features in their children and discussed them with clinicians as the first clues leading to the late diagnosis of Cohen syndrome.

Systematic anthropometric and cephalometric analysis of 14 individuals confirmed microcephaly, short philtrum, forward-inclined upper incisors, and maxillary prognathia [Hurmerinta et al 2002]. Long-term evaluation of six individuals with Cohen syndrome from three consanguineous families showed that the clinical features are stable over time [Peeters et al 2008].

Endocrine and obesity. Children with Cohen syndrome tend to manifest failure to thrive in infancy and early childhood, but subsequently become significantly overweight in their teenage years. More than 80% of individuals in the NCSD were reported to be underweight during early childhood, but overweight afterward. The obesity tends to be truncal in nature. The average age of the onset of obesity is 11.3 years (14.6 years in individuals of Amish descent and 8.4 years in individuals of non-Amish ancestry). The authors have noted that this change usually occurs very rapidly, with a weight gain of 10-15 kg seen over a period of four to six months. In contrast to Prader-Willi syndrome, appetite and food intake are not significantly increased during this time period and activity is not noticeably decreased.
Among individuals in the NCSD, the prevalence of short stature is approximately 65% and delayed puberty 74%; clinical endocrinologic evaluations did not identify explanations for these findings. Adult height in six affected individuals from three families was at or below the 3rd centile, with body mass index (BMI) ranging from 20.1 to 30.8 [Peeters et al 2008]. A study of ten affected individuals from nine families ranging in age from 5 to 52 years found short stature in seven and truncal obesity in eight; BMI ranged from 21.8 to 32.2 [Katzaki et al 2007]. Extensive endocrine evaluations of pituitary, adrenal, and thyroid function in the cohort of Finnish descent showed no significant abnormalities [Kivitie-Kallio et al 1999a].
Growth hormone deficiency was reported in a girl who was clinically diagnosed with Cohen syndrome [Massa et al 1991] but whose phenotype differed considerably from that seen in individuals with genetically confirmed Cohen syndrome. Three other individuals with Cohen syndrome who had growth hormone deficiency displayed catch-up growth following initiation of growth hormone replacement therapy [Author, personal observation]. The prevalence of growth hormone deficiency in Cohen syndrome is unknown.

Psychological and behavioral. Individuals with Cohen syndrome are typically described as having a “cheerful and friendly disposition.”
While cognitive ability varies, the majority of affected individuals fall into the moderate-to-profound range of intellectual disability [Kivitie-Kallio et al 1999b, Chandler et al 2003b, Karpf et al 2004]. Independence levels are generally poor but socialization skills are relatively less impaired; indeed, sociability is characteristic of individuals with Cohen syndrome. In contrast, psychological evaluations performed in previous studies have identified maladaptive and autistic-type behavior in some individuals [Kivitie-Kallio et al 1999b, Chandler et al 2003b, Karpf et al 2004]. Detailed psychometric and behavioral analyses did not identify any severe behavioral problems in six affected adults but confirmed a wide range of dysfunction related to individual degree of intellectual and visual disability [Peeters et al 2008].

Hematologic. Neutropenia, defined as an absolute neutrophil count (ANC) lower than 1,500/mm3 is mild to moderate, non-cyclic, and usually not fatal [Kivitie-Kallio et al 1997; Author, unpublished data]. However, recurrent infections and aphthous ulcers have been described in affected individuals [Falk et al 2004]. ANC usually falls into the range of 500 to 1,200/mm3 in all age groups [Author, unpublished data]. Furthermore, low-normal neutrophil counts are common in individuals who do not have frank neutropenia. However, the neutropenia may not necessarily result in an overall low white blood cell count and therefore may be overlooked for many years in some individuals.
More than 65% of affected individuals experience repeated oral mucosal ulcers and gingival infections, prophylactic granulocyte colony-stimulating factor (G-CSF) therapy has been commonly used in these individuals. The etiology of the neutropenia remains unclear. Bone marrow examination performed by the Finnish groups showed a normocellular or hypercellular marrow, with a left-shifted granulopoiesis in about half of those affected. No hematologic malignancies have been reported.

Immunologic and rheumatologic. While neutropenia may contribute to the compromise of immune function in some individuals with Cohen syndrome, it is not clear if it is the sole cause of the dysfunction. More than 80% of children in the NCSD have had more than five episodes of otitis media per year and most of them had tympanostomy tubes placed during early childhood. The majority of children also had an average of 2.5 lifetime episodes of pneumonia.
The frequency and severity of infections in individuals with Cohen syndrome appears to correlate poorly with ANC; individuals with frequent infections have an ANC in the same range as those without increased infections (500-1,200/mm3). Increased neutrophil adhesive capability has been reported in an individual with Cohen syndrome [Olivieri et al 1998].
Other immune disturbances have been observed: De Ravel et al [2002] found rheumatoid arthritis in an individual with Cohen syndrome, and frequent uveitis and recurrent pericarditis have been seen in affected individuals [Author, personal observation].

Musculoskeletal. Individuals with Cohen syndrome have characteristic narrow hands and feet, and slender fingers that have frequently been falsely reported to be long. The fingers are in fact short, as shown by hand x-ray analysis of the metacarpophalangeal pattern [Kivitie-Kallio et al 1999a].

Neurologic. Seizures have been reported in a minority of individuals with Cohen syndrome [Coppola et al 2003, Atabek et al 2004]. Anecdotally, two individuals in the NCSD cohort with epilepsy requiring anticonvulsants have phenotypes at the more severe end of the Cohen syndrome spectrum, characterized by an inability to communicate verbally. However, most individuals in the Finnish cohort, particularly those older than age five years were reported to have low-voltage EEGs without irritative spikes or epileptiform foci [Kivitie-Kallio et al 1999b].
Magnetic resonance imaging (MRI) of 18 individuals with Cohen syndrome found normal gray and white matter signal intensity but a relatively enlarged corpus callosum compared to 26 controls [Kivitie-Kallio et al 1998], although this abnormal finding appeared to be subtle and nonspecific.
Electromyography is reported to be normal [Kivitie-Kallio et al 1999b].

Cardiovascular. The cardiovascular system is not commonly affected in individuals with Cohen syndrome. An earlier report of mitral valve prolapse in individuals with Cohen-like syndrome of Ashkenazi Jewish ancestry [Sack & Friedman 1980] may be referring to another syndrome. Cardiac evaluation in 22 individuals of Finnish descent identified decreased left ventricular function with advancing age but no evidence for clinically significant mitral valve prolapse [Kivitie-Kallio et al 1999a]. Of the approximately 20 individuals in the NCSD who have had echocardiograms, none showed evidence of mitral valve prolapse.

Other. A majority of infants with Cohen syndrome have an unusually high-pitched and weak cry. Overall, 80% of parents with children in the NCSD recall this cry as resembling a kitten mewing. However, this unique cry is frequently overlooked by clinicians and has not been reported in the medical literature. The cause of the unusual cry in Cohen syndrome remains unknown, although laryngeal abnormalities postulated to cause the ""mewing cry"" seen in cri-du-chat syndrome have also been found in some individuals with Cohen syndrome [Chandler et al 2003a].

SYNDROME CHARACTERISTICS:
PENETRANCE: 100%
PREVALENCE: Unknown in the general population, 1 in 500 in the Ohio Geauga Old Order Amish settlement. 200+ affected individuals reported in the literature.
LIFE EXPECTANCY: Unknown. Oldest known patient living is 54 years-old.
AGE OF ONSET: Newborn
PRENATAL PRESENTATION: Reduced fetal movement (by report of ~50% mothers)

MOLECULAR GENETICS:
KNOWN MUTATION(S): c.8459T>C or 9258_9259insT (Amish), c.3348_3349delCT (Finnish) plus over 300 more pathogenic or likely pathogenic variants listed in Clinvar (https://www.ncbi.nlm.nih.gov/clinvar/?term=vps13b%5Bgene%5D)
TYPE OF MUTATION(S): Sequence variants ~70%, deletion/duplication ~30%
GENOTYPE/PHENOTYPE CORRELATION: None identified

KEY CLINICAL FEATURES/PHENOTYPES:
Abnormality of head or neck:
Typical Cohen syndrome facial gestalt: thick hair and eyebrows, long eyelashes, wave-shaped palpebral fissures, broad nasal tip, smooth or short philtrum, and hypotonic appearance (90-100%)
Low hairline (90-100%)
Thick eyebrows (90-100%)
Prominent nasal root
High, narrow palate
Prominent upper central incisors
Maxillary prognathism
Acquired microcephaly (>90%)
Abnormality of the voice:
High pitched and weak cry
Abnormality of the skeletal system:
Small or narrow hands and feet
Slender fingers
Kyphosis
Scoliosis
Pes planovalgus
Abnormality of the nervous system
Friendly disposition, overly sociable behavior
Relatively enlarged corpus callosum (via MRI)
Non-progressive intellectual disability and global developmental delay (100%)
Friendly disposition, overly sociable behavior
Seizures (minority)
Abnormality of prenatal development or birth
Decreased fetal movement (50%)
Abnormality of connective tissue
Joint hypermobility
Abnormality of the musculature
Motor clumsiness (>90%)
Hypotonia (100% and improves over time)
Growth abnormality
Failure to thrive (80%)
Truncal obesity appearing in or after mid-childhood with slender extremities (>80%)
Growth hormone deficiency (10-25%)
Short stature (65%)
Delayed puberty (74%)
Abnormality of the eye
Retinal dystrophy appearing by mid-childhood (>90%)
Progressive high myopia (>90%)
Nyctalopia (night blindness)
Late-onset lens subluxation
Astigmatism
Strabismus
Microcornea
Coloboma of the retina or lids
Congenital ptosis
Exophthalmos
Retinal detachment
Abnormality of the immune system
Aphthous ulcers and gingival infections (65%)
Recurrent infection (>90%)
Frequent uveitis
Recurrent pericarditis
Abnormality of blood and blood-forming tissues
Neutropenia (>90%)

KEY PUBLICATIONS:
Cohen et al [1973] described a pattern of abnormalities – intellectual deficiency, hypotonia, obesity, high nasal bridge, and prominent central incisors – observed in a pair of sibs and one unrelated individual. Norio et al [1984] observed six individuals of Finnish descent with the same disorder, known by them as ""Pepper syndrome,"" from the family name. They identified consanguinity among two pairs of parents (confirming autosomal recessive inheritance for this disorder), intermittent granulocytopenia, and marked ophthalmologic changes including decreased visual acuity, hemeralopia (day blindness), constricted visual fields, chorioretinal dystrophy with bull's-eye-like maculae and pigmentary deposits, optic atrophy, and isoelectric electroretinogram.

Cohen syndrome has been confirmed on almost all continents and in a wide variety of ethnic groups [Falk et al 2004, Hennies et al 2004, Kolehmainen et al 2004, Mochida et al 2004, Kondo et al 2005, Katzaki et al 2007, Taban et al 2007, Bugiani et al 2008, Peeters et al 2008, Balikova et al 2009, Rejeb et all 2017]. Cohen syndrome is overrepresented in the Finnish population [Kolehmainen et al 2003] with a phenotype comparable to that seen in individuals of non-Finnish descent [Chandler et al 2003a]. It is also overrepresented in the Ohio Geauga Old Order Amish settlement [Falk et al 2004].

Homozygous or compound heterozygous pathogenic variants are identified in approximately 70% of individuals with Cohen syndrome. [Balikova et al 2009, Seifert et al 2009, El Chehadeh-Djebbar et al 2011]. Altered splicing or deletion/duplication of VPS13B exon(s) also results in pathogenic alleles [Kolehmainen et al 2004, Balikova et al 2009, Parri et al 2010]. Analyzing the data pooled from several different studies, El Chehadeh-Djebbar et al [2011] concluded that copy number variations including deletion and duplication may be detected in 33% of families with Cohen syndrome.

SURVEILLANCE:
Annual ophthalmologic evaluation should assess visual acuity, refractive error, cataracts in older individuals, and/or retinal dystrophy.
Annual hematologic evaluation should include complete blood count and differential to assess neutropenia. More frequent monitoring may be needed for individuals with lower ANC or more frequent infections.
Growth and weight gain should be monitored.

MANAGEMENT AND TREATMENT:
Ophthalmologic issues are among the most concerning for families of individuals with Cohen syndrome registered in the National Cohen Syndrome Database. Management includes the following:
• Spectacle correction of refractive errors
• Low vision assessment with training as needed for the visually impaired
• Psychosocial support for affected individuals and their families
Early intervention and physical, occupational, and speech therapy are appropriate to address gross developmental delay, hypotonia, joint hypermobility, and motor clumsiness.
If neutropenia is documented, consideration may be given to the use of granulocyte-colony stimulating factor (G-CSF). In a study reported by Kivitie-Kallio et al [1997] response to adrenaline stimulation and to hydrocortisone was subnormal in 12 of 14 individuals and in eight of 16 individuals, respectively. However, recombinant G-CSF, administered to three individuals in the study, caused granulocytosis in all three.
Recurrent infections should be treated per standard therapy.

CLINICAL TRIALS:
N/A

PATIENT ORGANIZATIONS:
Cohen Syndrome Association: http://www.cohensyndrome.org/


DATE OF UPDATE:
May 21, 2018

* This information is courtesy of the L M D.
If you find a mistake or would like to contribute additional information, please email us at: [email protected]

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