Cohen syndrome is a rare genetic disorder caused by mutations in the VPS13B gene, inherited in an autosomal recessive pattern, meaning a child must receive a faulty copy from each parent to be affected. It brings together an unusual constellation of features: intellectual disability, a distinctive facial appearance that changes markedly with age, progressive vision loss, low white blood cell counts, and a notably cheerful temperament. Because many of its hallmarks emerge gradually and overlap with other conditions, Cohen syndrome is frequently underdiagnosed or misdiagnosed, sometimes for years.
The Genetic Cause
Cohen syndrome traces to mutations in a single gene called VPS13B (sometimes referred to by its earlier name, COH1), located on chromosome 8q22. The gene is large, spanning dozens of coding segments, and more than 150 different mutations have been catalogued across over 200 confirmed patients worldwide.1PubMed Central. A novel VPS13B mutation in Cohen syndrome: a case report and review of literature Missense and nonsense mutations are the most commonly identified types, though deletions, insertions, and splice-site changes also occur. The diversity of mutations partly explains why the severity and combination of symptoms can vary so much from one person to the next.
VPS13B belongs to a family of four human genes (VPS13A through VPS13D), all related to a yeast gene involved in sorting proteins within cells. Each family member is linked to a different disease: VPS13A mutations cause chorea-acanthocytosis, a movement disorder with abnormally shaped red blood cells, while VPS13C and VPS13D have been connected to other neurological conditions.2PubMed. Analysis of the human VPS13 gene family VPS13B is specifically involved in the development of the eyes, blood system, and central nervous system, which explains the pattern of organs affected in Cohen syndrome.3PubMed Central. A novel VPS13B mutation in Cohen syndrome: a case report and review of literature
What VPS13B Does Inside Cells
At the cellular level, VPS13 proteins act as lipid transporters, moving fats from one membrane to another within the cell. VPS13B parks itself at the Golgi complex, the cell’s main packaging and shipping center, where it sits at the boundary between different Golgi compartments.4PubMed Central. Stairway to the Golgi: Two paths VPS13B can go by Recent research has shown that when VPS13B is absent, the Golgi complex has trouble reassembling after disruption, suggesting the protein is critical for maintaining the structural integrity of this organelle.5Journal of Cell Biology. VPS13B is localized at the interface between Golgi cisternae and is a functional partner of FAM177A1 A malfunctioning Golgi disrupts the processing and delivery of proteins throughout the cell, which helps explain why Cohen syndrome affects so many organ systems at once. Tissues that depend heavily on efficient protein trafficking during development, like the brain and retina, are hit hardest.
Facial Features That Change with Age
One of the trickiest aspects of diagnosing Cohen syndrome is that the face looks quite different in infancy than it does in later childhood. Babies with the condition often resemble infants with Prader-Willi syndrome: they have low muscle tone, small hands, a round face with full cheeks, almond-shaped eyes, and a small jaw. Starting around age four, the face begins to elongate and become more oval. By about age nine, the characteristic Cohen syndrome appearance is usually recognizable: a long face, a nose sometimes described as beak-shaped, and an open-mouth expression with prominent upper central incisors.6PubMed. Early Diagnostic Signs and the Natural History of Typical Findings in Cohen Syndrome
Detailed measurements of the skull and face confirm several consistent findings. Head size is small, averaging about four standard deviations below normal, and the base of the skull is short. The upper face tends to be close to normal width, but the lower face is narrow. The groove between the nose and upper lip (the philtrum) is shorter than typical, and the upper front teeth tilt forward.7PubMed. Craniofacial features in Cohen syndrome: an anthropometric and cephalometric analysis of 14 patients These measurements are useful for clinicians, but the key practical point for families is that the recognizable facial pattern may not be obvious until school age, and clinicians who encounter the syndrome only in textbook photos of older children may not connect the dots in a toddler.
Ethnic Variation in Appearance
The facial gestalt of Cohen syndrome is strikingly consistent among affected individuals within the same ethnic group, but it can look quite different across populations. Research in the Ohio Amish community, which has a higher carrier rate due to a founder effect, identified affected individuals whose facial features did not match the classic Finnish description of the syndrome, even though the same gene was responsible. The researchers concluded that facial appearance is an unreliable diagnostic indicator when comparing across ethnic backgrounds.8PubMed. Cohen syndrome in the Ohio Amish This is a meaningful pitfall: a clinician familiar with Cohen syndrome only from descriptions of Finnish or Northern European patients might not recognize it in a child from a Middle Eastern, Asian, or Amish family.
Progressive Vision Loss
Eye problems are among the most medically significant features of Cohen syndrome. About 70% of affected individuals develop high myopia (severe nearsightedness) by their teens, and retinal dystrophy, the progressive degeneration of the light-sensing tissue in the back of the eye, is common. One study found early signs of retinal disease in 80% of patients under age five, which is earlier than many clinicians previously expected.9PubMed Central. The ophthalmic findings in Cohen syndrome The retinal changes have a characteristic appearance: chorioretinal dystrophy that can include a bull’s-eye pattern at the center of the retina and pigment deposits, along with optic nerve pallor.10PubMed Central. Ophthalmic findings in Cohen syndrome patient without subjective ophthalmic complaints: A case report
What makes this especially important is that some patients do not report visual complaints even when significant retinal changes are already underway. A case report documented advanced ophthalmic findings in a patient who had no subjective eye symptoms at all.11PubMed Central. Ophthalmic findings in Cohen syndrome patient without subjective ophthalmic complaints: A case report This means regular eye exams, including retinal imaging, are critical for anyone with Cohen syndrome, even if they seem to see well. The combination of high myopia and progressive retinal degeneration is the main cause of vision loss in these patients, and early identification allows for supportive interventions like corrective lenses, low-vision aids, and planning for potential visual decline.
Neutropenia and Infections
A hallmark blood finding in Cohen syndrome is a chronically low neutrophil count, the white blood cells most responsible for fighting bacterial infections. Neutropenia was recognized as a feature of the syndrome relatively early in its study and has since been described as one of its most consistent manifestations.12PubMed Central. Cohen Syndrome: Review of the Literature In some cases, it may be the earliest clinical sign, prompting the genetic workup that leads to diagnosis.13PubMed Central. Neutropenia is a consistent and the earliest manifestation of Cohen’s syndrome: three cases and two novel variants in VPS13B gene
The low counts tend to be mild to moderate, non-cyclic (meaning they stay persistently low rather than dipping and recovering in a repeating pattern), and are not typically life-threatening. However, they do translate to increased susceptibility to infections, particularly of the gums and skin. Patients commonly experience prolonged or recurrent infections in these areas.14PubMed. Granulocytopenia in Cohen syndrome Interestingly, the rate of neutropenia appears to vary by ethnicity: a large literature review found that roughly 90% of Caucasian patients had reduced neutrophil levels, compared with about 59% of Arab patients and 47% of Asian patients.15PubMed. Granulocytopenia in Cohen syndrome Whether this reflects differences in underlying mutations, modifier genes, or how different populations define and measure neutropenia remains unclear.
Dental and Gum Disease
The combination of chronic neutropenia and prominent upper incisors creates a perfect storm for dental problems. People with Cohen syndrome show significantly more alveolar bone loss (the bone that holds teeth in place) than controls of similar age, and the bone loss tends to be more extensive.16PubMed. Periodontal findings in Cohen syndrome with chronic neutropenia The researchers tied this increased susceptibility to early periodontal breakdown directly to the persistent neutropenia, since neutrophils are a frontline defense against the bacteria that cause gum disease. For families and care teams, this means aggressive preventive dental care starting early: frequent cleanings, close monitoring for signs of gum inflammation, and possibly antimicrobial mouth rinses. Waiting until gum problems become obvious often means significant bone has already been lost.
Intellectual Disability and the Friendly Personality
Cognitive delays in Cohen syndrome are present from early on and tend to be stable rather than worsening over time. Most individuals have mild to moderate intellectual disability alongside motor clumsiness, low muscle tone in childhood, and joint hypermobility.17PubMed. Cohen Syndrome: Essential features, natural history, and heterogeneity – Section: Abstract Speech is often delayed, and fine motor tasks can be challenging.
One of the most consistently described traits, and the one that families and clinicians often mention first, is an exceptionally sociable and cheerful temperament. Formal behavioral assessment has found that people with Cohen syndrome score high on positive domains like self-direction, responsibility, and socialization, while maladaptive behavior is almost entirely absent.18PubMed. Cohen Syndrome: Essential features, natural history, and heterogeneity – Section: Abstract This friendly disposition is consistent enough to be considered a diagnostic feature. Animal research has begun to probe the neurobiology behind it: a mouse model of Cohen syndrome showed neuroanatomical and behavioral changes, with female mice less affected than males, hinting at possible sex-based differences in severity.19PubMed. Characterization of Vps13b-mutant mice reveals neuroanatomical and behavioral phenotypes with females less affected
Some families of children later diagnosed with Cohen syndrome report that autism spectrum features were noted early on, including social communication differences and restricted interests. At least one confirmed case initially presented with autism-like features before the genetic diagnosis was made.20PubMed Central. First case report of Cohen syndrome in the Tunisian population caused by VPS13B mutations This is worth noting because the characteristic friendliness that appears later could lead clinicians away from considering Cohen syndrome in a young child who initially seems withdrawn.
An Unusual Brain Structure Finding
Brain imaging in Cohen syndrome reveals a surprising detail: the corpus callosum, the thick bundle of nerve fibers connecting the two brain hemispheres, is relatively large compared to overall brain size. This is counterintuitive because in most conditions that feature microcephaly and intellectual disability, the corpus callosum is small or thin. In Cohen syndrome, while the brain itself and the brain stem are both markedly smaller than average, the central portion of the corpus callosum is actually bigger than in controls.21PubMed. MRI of the brain in the Cohen syndrome: a relatively large corpus callosum in patients with mental retardation and microcephaly Researchers noted this as a finding without parallel in other intellectual disability syndromes. Whether this enlarged connection between hemispheres plays any role in the sociable behavior typical of the syndrome is purely speculative at this point, but it does serve as a potentially useful radiological marker.
Truncal Obesity with Slender Limbs
Body shape in Cohen syndrome follows a distinctive pattern: excess weight accumulates around the trunk while the arms and legs remain relatively thin. This truncal obesity often develops during childhood or adolescence and contrasts with the overall slender build of the extremities, creating a body habitus that is fairly specific to the condition.22PubMed. Cohen syndrome with novel VPS13B variants presenting as early-onset diabetes: a case report The metabolic consequences deserve attention. At least one case has been documented where the truncal obesity progressed to early-onset diabetes, suggesting that metabolic screening should be part of ongoing management. Routine pituitary, adrenal, and thyroid function, however, tend to be normal.23PubMed. Cohen syndrome: evaluation of its cardiac, endocrine and radiological features
Getting to a Diagnosis
Cohen syndrome is diagnosed through a combination of clinical recognition and genetic testing, and in practice the genetic test often leads the way. The clinical picture alone can be ambiguous, especially in young children whose facial features have not yet matured or in populations where the expected facial gestalt does not match published descriptions. Whole exome sequencing has become a powerful tool for confirming the diagnosis, sometimes in families where no one had suspected Cohen syndrome at all. In one Saudi family, clinical assessment could not establish the diagnosis, but genetic analysis revealed a mutation in VPS13B and confirmed the condition.24PubMed. Homozygosity mapping and whole exome sequencing provide exact diagnosis of Cohen syndrome in a Saudi family
The classic diagnostic criteria look for the combination of stable intellectual disability, microcephaly, the characteristic facial features (in patients old enough to show them), childhood hypotonia with joint hypermobility, retinal dystrophy and myopia (typically after age five), and low neutrophil counts.25PubMed. Cohen Syndrome: Essential features, natural history, and heterogeneity – Section: Abstract Not every patient checks every box, and that is where genetic testing becomes essential. A child referred for unexplained neutropenia, or an adolescent with worsening vision and intellectual disability, may have the diagnosis uncovered through broad-panel genetic testing rather than a clinician recognizing the full syndrome clinically.
Conditions That Look Similar
Cohen syndrome overlaps clinically with several other genetic conditions, and sorting them out matters because management differs. Bardet-Biedl syndrome is probably the most commonly confused alternative, since both can feature early visual impairment, obesity, and intellectual disability.26PubMed. Cohen Syndrome: Essential features, natural history, and heterogeneity – Section: Abstract Bardet-Biedl, however, typically includes polydactyly (extra fingers or toes) and kidney abnormalities, neither of which is part of Cohen syndrome. The pattern of retinal disease also differs: Bardet-Biedl causes rod-cone dystrophy that often leads to night blindness first, while Cohen syndrome’s retinal dystrophy tends to follow a different course with the bull’s-eye macular pattern.
Prader-Willi syndrome enters the picture mainly in infancy, when babies with Cohen syndrome can look almost indistinguishable from babies with Prader-Willi: floppy, poor feeders, with characteristic facial features including a round face and small jaw.27PubMed. Early Diagnostic Signs and the Natural History of Typical Findings in Cohen Syndrome Prader-Willi is caused by a completely different genetic mechanism (loss of paternal chromosome 15q material), and its behavioral profile in later childhood, marked by insatiable appetite and behavioral outbursts, diverges sharply from the cheerful, cooperative temperament of Cohen syndrome. If a baby initially suspected of having Prader-Willi tests negative on methylation analysis, Cohen syndrome should be on the differential.
Carrier Parents and Family Planning
Because Cohen syndrome follows autosomal recessive inheritance, both parents of an affected child are carriers who each have one working and one non-working copy of VPS13B. Carriers are healthy and show no signs of the condition. Each pregnancy between two carriers has a one-in-four chance of producing an affected child. Consanguineous families (where parents share recent ancestry) have a higher probability of both parents carrying the same mutation, which is why Cohen syndrome is reported more frequently in populations with higher rates of consanguinity or in genetically isolated communities like the Finnish population and the Ohio Amish.28PubMed. Cohen syndrome in the Ohio Amish Compound heterozygosity, where a child inherits two different mutations in VPS13B (one from each parent), is also well documented and can make carrier detection through targeted single-mutation testing insufficient. Whole exome or gene-panel sequencing addresses this by screening the entire gene.29PubMed Central. First case report of Cohen syndrome in the Tunisian population caused by VPS13B mutations
Living with Cohen Syndrome
There is no cure for Cohen syndrome, and management is supportive and multidisciplinary. For families navigating the condition, the practical priorities tend to be organized around the organ systems most affected. Regular ophthalmology visits with retinal imaging should begin in early childhood, given that retinal changes can appear before age five and before the child reports any difficulty seeing.30PubMed Central. The ophthalmic findings in Cohen syndrome Complete blood counts should be monitored to track neutrophil levels, and families should be aware that gum infections, skin infections, and slow wound healing may signal that counts are particularly low. Dental care, including frequent professional cleanings and close attention to gum health, helps slow the periodontal disease that commonly develops.31PubMed. Periodontal findings in Cohen syndrome with chronic neutropenia
Physical therapy and occupational therapy address the hypotonia and motor clumsiness, while speech therapy supports language development. Educational plans tailored to the child’s cognitive level, along with social skills support that capitalizes on their natural sociability, tend to be well received. The metabolic picture warrants monitoring as the person ages, with screening for insulin resistance and diabetes given the truncal obesity pattern.32PubMed. Cohen syndrome with novel VPS13B variants presenting as early-onset diabetes: a case report Adults with Cohen syndrome typically remain sociable and engaged with their communities, and with consistent support many achieve a good quality of life, even as vision and other challenges evolve over time.