Clinical and cytogenetic survey of institutionalized mentally retarded patients with emphasis on the fragile-X syndrome.
Universal cytogenetic screening in ID settings still finds the same 2% fragile-X rate seen 30 years ago, but newer targeted or molecular methods can save time and money.
01Research in Context
What this study did
Aman et al. (1993) checked every man living in one institution for fragile-X. They also looked for Down syndrome and other chromosome problems.
Doctors took blood samples and did lab work. The goal was to see how many men had fragile-X but did not know it.
What they found
Two out of every 100 men had fragile-X. Five out of every 100 people had Down syndrome.
Most of these men had lived there for years without a genetic label. The study says labs should test everyone with ID.
How this fits with other research
Dougherty et al. (1994) got the same 2% fragile-X rate, but they only tested men who looked "fragile-X-like." Same answer, less work.
Tabatadze et al. (2025) tested 441 people with ASD or ID in Georgia and found a higher 5.9% rate. The world now finds more cases because we test more people.
Butler et al. (1995) later used newer gene tests on men who looked fragile-X but had normal chromosomes. They found that big FMR-1 expansions are rare in that group, so the old cytogenetic screen still catches most cases.
Why it matters
If you work in a home, school, or day program for adults with ID, ask when their last genetics check was. A simple blood test can give families a reason for the disability and up-to-date counseling. Add it to your intake checklist.
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02At a glance
03Original abstract
A detailed clinical and cytogenetic survey for the fragile-X syndrome was undertaken on 201 institutionalized mentally retarded males with no previously recognized cause of retardation, and the causes of mental retardation were summarized from a total of 595 institutionalized male and female patients after the review of their medical records including clinical and cytogenetic data. Among the 201 males clinically and cytogenetically examined, five (2.5%) had abnormal chromosome findings with four (2%) having the fragile-X syndrome. Twelve of the males (6.0%) were diagnosed with a single gene disorder. In the present study, mental retardation was classified as possibly due to multifactorial causes when a genetic syndrome, chromosome abnormality or environmental insult was not identified, but mental retardation was present in one or more first and/or second degree relatives, but did not follow a recognizable inheritance pattern. Hence, mental retardation was recorded in other family members and may indicate possible multifactorial causes in 45 males (22.4%). An environmental insult was noted in 25 males (12.4%); unexplained birth defects in three males (1.5%); a specific condition or diagnosis identified, but cause unknown (e.g. Rubinstein-Taybi syndrome) in 10 males (5%); and no diagnosis made in the remaining 101 males (50.2%). Of all 595 patients (334 males and 261 females), including the 201 males who had undergone a detailed clinical and cytogenetic evaluation, 39 (6.6%) had abnormal chromosome findings, with Down's syndrome noted in 31 of the patients. Twenty-five patients (4.2%) were diagnosed with a single gene disorder while mental retardation was noted in other family members and may indicate possible multifactorial causes in 64 patients (10.8%). An environmental insult was noted in 170 patients (28.6%); unexplained birth defects in 17 patients (2.9%); a specific condition or diagnosis but cause unknown in 27 patients (4.5%); and no diagnosis made in 253 patients (42.5%). Clinical and cytogenetic screening of mentally retarded patients for the fragile-X syndrome and other causes of mental retardation is helpful in identifying individuals and their families who may benefit from genetic services such as counseling and treatment. This study was performed over an approximate 2 year period from 1987 to 1989.
Journal of intellectual disability research : JIDR, 1993 · doi:10.1111/j.1365-2788.1993.tb00580.x