Patients with Weaver Syndrome show growth and bone development (maturation) that is faster than normal but a weight to height relationship that is normal or above. Among a few patients, symptoms may not be evident until several months after birth. Patients may show progressive increases in muscle tone (hypertonia) with exaggerated reflexes (spasticity) and/or slow development of voluntary movements (psychomotor retardation). Babies with this syndrome have a hoarse low-pitched cry.
Individuals with Weaver Syndrome may have extremely wide-set eyes (hypertelorism), sometimes with excess skin over the inner corner of the eyes (epicanthal folds), or other eyelid abnormalities (downslanting palpebral fissures). The back part of the head (occiput) may be flat, the forehead broad, and the ears unusually large. The natural groove located above the upper lip and below the nose (philtrum) may be longer than average. The jaw may appear somewhat smaller than normal (micrognathia). Other physical characteristics can include thin hair, inverted nipples and skin which appears somewhat loose.
Thumbs of people with Weaver Syndrome are usually broad. One or more fingers may be permanently bent (camptodactyly). Nails can be deep-set and thin. The pads of the fingertips are usually prominent. Malformed toes (clinodactyly), an abnormally high arch (pes cavus), a clubfoot with the sole of the foot turned inward and upward either in the direction of the heel (talipes equinovarus) or of the toes (talipes calcaneovalgus), or a twisted foot (metatarsus adductus) may be present. Individuals may not be able to extend their elbows or knees out very far.
The exact cause of Weaver Syndrome is unknown. Some researchers think, because there have been some cases of mildly affected mothers having sons who are more severely affected, that Weaver Syndrome may be inherited as an autosomal dominant trait with a gender-limited expression of symptoms, or an X-linked recessive trait. Others think that it may be an autosomal recessive trait. In some cases there are no signs of heredity in a family and the cause is unknown.
Human traits, including the classic genetic diseases, are the product of the interaction of two genes, one received from the father and one from the mother.
In dominant disorders, a single copy of the disease gene (received from either the mother or father) will be expressed “dominating” the other normal gene and resulting in the appearance of the disease. The risk of transmitting the disorder from affected parent to offspring is 50 percent for each pregnancy regardless of the sex of the resulting child.
X-linked recessive disorders are conditions that are coded on the X chromosome. Females have two X chromosomes, but males have one X chromosome and one Y chromosome. Therefore, in females, disease traits on the X chromosome can be masked by the normal gene on the other X chromosome. Since males only have one X chromosome, if they inherit a gene for a disease present on the X, it will be expressed. Men with X-linked disorders transmit the gene to all their daughters, who are carriers, but never to their sons. Women who are carriers of an X-linked disorder have a 50 percent risk of transmitting the carrier condition to their daughters, and a 50 percent risk of transmitting the disease to their sons.
In recessive disorders, the condition does not appear unless a person inherits the same defective gene for the same trait from each parent. If an individual receives one normal gene and one gene for the disease, the person will be a carrier for the disease, but usually will not show symptoms. The risk of transmitting the disease to the children of a couple, both of whom are carriers for a recessive disorder, is 25 percent. Fifty percent of their children risk being carriers of the disease, but generally will not show symptoms of the disorder. Twenty-five percent of their children may receive both normal genes, one from each parent, and will be genetically normal (for that particular trait). The risk is the same for each pregnancy.
Weaver Syndrome is a rare disorder affecting males three times more often than females. The syndrome is usually present before birth (prenatal onset).
Treatment of Weaver Syndrome is symptomatic and supportive. An orthopedist can be consulted for correction of foot deformities. Genetic counseling may be of benefit to patients and their families.
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A Probable Case of Familial Weaver Syndrome Associated with Neoplasia. C. Derry et al., J Med Genet (September, 1999; 36 (9)). Pp. 725-28.
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The Syndromes of Marshall and Weaver. N. Fitch; J Med Genet (Jun 1980; issue 17 (3)). Pp. 174-178.
Weaver Syndrome with Pes Cavus. S. A. Farrell and H. E. Hughes; Am J Med Genet (Aug 1985; issue 21 (4)). Pp. 737-739.
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