Smith-Fineman-Myers syndrome (SFMS) is a rare and severe type of X-linked inherited mental retardation.

Smith-Fineman-Myers syndrome is also known as Smith-Fineman-Myers type mental retardation and Smith-Fineman-Myers type X-linked mental retardation. SFMS results in severe mental retardation along with characteristic facial features and skeletal differences.

Smith-Fineman-Myers syndrome is an X-linked disease. X-linked diseases map to the human X chromosome, a sex chromosome. Females have two X chromosomes, whereas males have one X chromosome and one Y chromosome. Because males have only one X chromosome, they require only one copy of an abnormal X-linked gene to display disease. Because females have two X chromosomes, the effect of one X-linked recessive disease gene is masked by the disease gene's normal counterpart on her other X chromosome.

In classic X-linked inheritance males are affected, presenting full clinical symptoms of the disease. Females are not affected. Affected fathers can never pass...