Cohen's syndrome with diabetes mellitus

Cohen Syndrome: Review of the Literature

Cohen syndrome was initially described as a syndrome including obesity, hypotonia, mental deficiency, and facial, oral, ocular and limb anomalies. Leukopenia, especially neutropenia, was later described as a feature of Cohen syndrome. Cohen syndrome is caused by an autosomal recessive (AR) mutation of the vacuolar protein sorting 13 homolog B (VPS13B, also referred to as COH1) gene on chromosome 8q22.2.

Insulin response dysregulation explains abnormal fat storage and increased risk of diabetes mellitus type 2 in Cohen Syndrome

Cohen Syndrome (CS) is a rare autosomal recessive disorder, with defective glycosylation secondary to mutations in the VPS13B gene, which encodes a protein of the Golgi apparatus. Besides congenital neutropenia, retinopathy and intellectual deficiency, CS patients are faced with truncal obesity. Metabolism investigations showed abnormal glucose tolerance tests and low HDL values in some patients, and these could be risk factors for the development of diabetes mellitus and/or cardiovascular complications. To understand the mechanisms involved in CS fat storage, we used two models of adipogenesis differentiation: (i) SGBS pre-adipocytes with VPS13B invalidation thanks to siRNA delivery and (ii) CS primary fibroblasts. In both models, VPS13B invalidation led to accelerated differentiation into fat cells, which was confirmed by the earlier and increased expression of specific adipogenic genes, consequent to the increased response of cells to insulin stimulation. At the end of the differentiation protocol, these fat cells exhibited decreased AKT2 phosphorylation after insulin stimulation, which suggests insulin resistance. This study, in association with the in-depth analysis of the metabolic status of the patients, thus allowed us to recommend appropriate nutritional education to prevent the occurrence of diabetes mellitus and to put forward recommendations for the follow-up of CS patients, in particular with regard to the development of metabolic syndrome. We also suggest replacing the term obesity by abnormal fat distribution in CS, which should reduce the number of inappropriate diagnoses in patients who are referred only on the basis of intellectual deficiency associated with obesity.

Cohen syndrome: essential features, natural history, and heterogeneity

This article elucidates the clinical picture in Cohen syndrome (MIM 216550), an autosomal recessive disorder that is overrepresented in Finland. The diagnosis is based on the typical clinical picture: nonprogressive psychomotor retardation, motor clumsiness and microcephaly, typical facial features, childhood hypotonia and hyperextensibility of the joints, ophthalmologic findings of retinochoroidal dystrophy and myopia in patients over 5 years of age, and granulocytopenia. In a nationwide study, 29 Finnish patients were investigated. Magnetic resonance images of the brain with quantitative structure analyses revealed a relatively enlarged corpus callosum (CC). The youngest patients had normal EEGs, while all others had low-voltage EEGs. Of the patients, 22% had profound, 61% severe, 6% moderate, and 11% mild retardation. In an adaptive behavior scale (AAMD), patients had high scores in the positive domains (self-direction, responsibility, and socialization), whereas maladaptive behavior was almost lacking. Only the youngest patients had unimpaired visual function. Vision started to deteriorate early but slowly. Progressive myopia and retinochoroidal dystrophy were found in all of the patients over 5 years of age. All of the patients had isolated granulocytopenia. The heart anatomy was normal. However, decreased left ventricular function with advancing age was found. No significant endocrine abnormalities were discovered. Fingers were slender but short, with a typical metacarpophalangeal pattern profile. The manifestations vary at different ages. The Finnish Cohen patients are clinically highly homogeneous, their disease gene being located on chromosome 8. Heterogeneity probably exists among other patients claimed to have Cohen syndrome.

Ophthalmologic findings in Cohen syndrome. A long-term follow-up

OBJECTIVE

To determine the nature and course of ophthalmologic abnormalities and their clinical significance in Cohen syndrome.

STUDY DESIGN

Observational case series.

PARTICIPANTS

Twenty-two Cohen syndrome patients aged 2 to 57 years were examined, and a retrospective review of ophthalmologic records was carried out for 14 of them. All but one were part of the Finnish study of refined mapping of the Cohen syndrome gene by linkage disequilibrium in chromosome 8.

MAIN OUTCOME MEASURES

Visual acuity (VA), cycloplegic refraction, biomicroscopy, lens opacitometry, ophthalmoscopy, and fundus photography.

RESULTS

With the exception of the two youngest patients, all had symptoms such as nyctalopia, impaired vision, and visual field loss. Progressive, often high-grade myopia, astigmatism, and retinochoroidal dystrophy resembling retinitis pigmentosa occurred in all, except for the youngest patients. The earliest fundus changes were pale disc and pale fundus with or without pigment granularity, followed by narrowed vessels, pigment clumps, and bone spiculelike pigment accumulations by 10 to 20 years of age. Pigment deposits increased and approached the posterior pole by 35 to 40 years of age. Patients more than 45 years of age had severe retinochoroidal atrophy. A bull's-eye macula was seen in most patients. Teenagers had peripheral lens opacities, and young adults had early nuclear sclerosis confirmed by lens opacitometry. Older patients also had posterior subcapsular cataracts, iris atrophy, and iridophacodonesis. Vision started to deteriorate at the age of 6 to 10 years, but remained relatively good (VA 0.5-0.1) in most patients until 30 and, in one case, 46 years of age. Older patients were severely visually handicapped (VA hand motion to light perception), but none were completely blind.

CONCLUSIONS

Progressive myopia and retinochoroidal dystrophy are essential features in Cohen syndrome and, together with early lens opacities, lead to deterioration of vision. Cohen syndrome patients need careful ophthalmologic follow-up at all ages. Nyctalopia and restricted visual fields should be considered when planning the patient's daily activities.

Cohen syndrome: evaluation of its cardiac, endocrine and radiological features

Cohen syndrome (MIM no. 216550) is an autosomal recessive disorder with a typical clinical picture. Since the first report, most publications have represented single case reports. In this study, our aim was to describe cardiac, endocrine and radiological abnormalities in 22 Cohen patients of Finnish descent. Detailed investigations of the heart revealed the anatomy of the heart to be normal with no evidence for clinically significant mitral prolapse. However, a decreased left ventricular function with advancing age was identified. No significant endocrine abnormalities were found at the examination of pituitary, adrenal and thyroid function. The height was either normal or patients were moderately short (mean height standard deviation score (SDS) - 2) at all ages, associated, however, often with the marked kyphosis. Truncal obesity was seen in 4/22 patients. X-rays of the chest, lumbar and thoracic spine, long bones, ankles and metacarpophalangeal pattern profiles revealed kyphosis, scoliosis and calcaneo planovalgus as common features. Fingers of these patients were slender but short with a characteristic metacarpophalangeal pattern profile.

The Cohen syndrome: report of a case

We report on a sporadic case satisfied with a proposed diagnostic criteria for Cohen syndrome. This 10 year-old Japanese boy had truncal obesity, short stature, mild mental retardation, hypotonia, maxillary hypoplasia, micrognathia, narrow hands and feet, high-arched palate, prominent upper central incisors, high nasal bridge, but no pigmentary retinopathy. Autosomal recessive manner of inheritance was suggested by the pedigree.

Exclusion mapping of the Cohen syndrome gene from the Prader-Willi syndrome locus

Karyotype and DNA analyses using DNA probes were carried out in a family with the Cohen syndrome. Two affected brothers had normal chromosomal constitutions. A major deletion or duplication of genomic DNA fragments hybridized with the DNA probes, pML34 at D15S9 locus and pTD3-21 at D15S10 locus, assigned on 15q11-q12 was not detected in the patients. In addition, a linkage of the syndrome to D15S9 and D15S10 loci was not observed in the family. These data suggest that a gene for the Cohen syndrome is excluded from the 15q11-q12 region, on which a gene for the Prader-Willi syndrome is assigned, and that the Cohen syndrome is distinctly different from the Prader-Willi syndrome, although clinical manifestations of the Cohen and the Prader-Willi syndromes are very similar.

The Cohen syndrome: does mottled retina separate a Finnish and a Jewish type?

A new familial cases of the Cohen syndrome in two brothers of one-half second-cousin parents is reported. Typical clinical manifestations of the syndrome; i.e., mental deficiency, hypotonia, characteristic facial appearance, long, narrow hands and feet with elongated fingers, and mottled retinae were present in both patients. Both patients also had leukopenia. Clinical manifestations of the Cohen syndrome in patients are highly variable, and mottled retina has been observed in 22 of 87 patients (25%). However, an association of mottled retina in patients with the Cohen syndrome is likely to be related to the families and ethnic groups. Among 19 familial cases, mottled retina was observed in all affected sibs from five families, but in 13 families none of the affected sibs had the mottled retina. All Finnish patients had the mottled retina, but this was noted in only one of 39 Jewish patients. Based on these data, we hypothesize that two alleles at the gene locus for the Cohen syndrome exhibit different clinical manifestations: one is a Finnish type with mottled retina, and the other is a Jewish type without retinal anomalies.