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.