Down syndrome in a population of elderly mentally retarded patients: genetic-diagnostic survey and implications for medical care.

Ninety-six adults with Down syndrome (DS) from an institutional setting of 591 mentally retarded were investigated systematically with respect to cytogenetic diagnosis, mental functioning and dementia, ophthalmological and audiological abnormalities, and thyroid function. Seventy of the 96 DS patients (73%) were older than 40 years. Only 4.2% were females. Trisomy 21 was found in 86% and mosaic trisomy 21 in 13%. Eighty-two percent of the patients were moderately or severely mentally retarded, 15% were profoundly retarded, and only 3% mildly retarded. Nineteen percent of the patients had dementia. This number increased to 42% of the patients above the age of 50 years. Epileptic seizures were present in 16.7% of all patients, and in 50% of the patients with dementia. Only 17% of the patients in the present study had normal visual acuity, one-third had at least moderately reduced vision. This number increased significantly with age: in the age group 50-59 years almost half of the patients had moderate to severe vision loss. Seventy percent of the patients had moderate, severe, or very severe hearing loss, which was undiagnosed before systematic hearing testing was performed. Increased (48%) or decreased (1%) TSH level was found in 49% of the patients examined for thyroid functions. We suggest a regular screening of all adults with DS to diagnose early dementia, epilepsy, hypothyroidism, and early loss of visual acuity and hearing, with special attention to the group of patients who are severely to profoundly mentally retarded and those with advanced age. Cytogenetic studies are necessary to confirm the clinical diagnosis and are essential for genetic counseling purposes. Copyright 1999 Wiley-Liss, Inc.