Abnormalities of chromosome 18 in a girl with mental retardation and autistic disorder.

Doctors looked at one girl who had both autism and intellectual disability. They checked her chromosomes and found a rare mix-up on chromosome 18.

The report is a single-case study. It gives no numbers, no group, and no treatment test.

The girl carried a mosaic pattern: part of 18q was duplicated and part of 18p was missing. This exact pattern had not been seen before.

The authors say the finding shows chromosome 18 can be involved when autism and ID occur together.

Poulson (1998) reviewed many cytogenetic papers and named chromosome 15q and the sex chromosomes as the top autism leads. The 1993 case adds chromosome 18 to the list, extending the map beyond the "big two."

Green et al. (1986) already urged karyotyping for autism plus ID. Konstantareas et al. (1999) later screened 127 autistic children and found anomalies in only a small slice, showing such cases are rare but real. The single 1993 girl fits that rarity.

Together the papers say: most kids with autism have normal chromosomes, yet a few carry clear defects. When you see both autism and unexplained ID, a genetic work-up is still worth it.

You may never meet a client with chromosome 18 mosaicism, but the rule is practical. If a learner has autism plus global delays and no known cause, mention genetic referral to the family. A simple blood test can uncover rare syndromes, clarify prognosis, and guide medical care. Keep chromosome 18 in mind alongside the better-known 15q and fragile-X targets.