Category: Xa-Xz

A chromosome disorder in females caused by the presence of four X chromosomes rather than the usual two. The disorder is characterized by decreased intelligence (IQ 30 to 80; average 55), speech and behavioral problems, tall stature and reduced fertility. Also known as tetra-X syndrome.

A chromosome condition present in 1 in 1000 females, due to the presence of three X chromosomes rather than the usual two. The condition is associated with increased height but no malformations. Intelligence ranges from above normal to mild retardation. The average IQ is 85 to 90. Learning problems may be helped by early special education. Also…

A syndrome characterized by the presence of an XX sex chromosome complement in an individual with male genitalia including both testes but no sperm production (azoospermia). Babies with the XX male syndrome may come to medical attention at birth because of hypospadias (urethral opening not at its normal position at the end of the penis) or because of cryptorchidism (undescended testes). However, most individuals with the…

The sex chromosome complement of a normal human female.

Medical abbreviation for radiotherapy.

Dry mouth. Xerostomia can be associated with systemic diseases, such as Sjogren’s syndrome, systemic lupus erythematosus, and rheumatoid arthritis; and it can be a side effect of medication and poor dental hygiene. Xerostomia results from inadequate function of the salivary glands, such as the parotid glands. Treatment involves adequate intake of water, use of artificial saliva, and good dental care.…

Abnormal dryness of the skin, mucous membranes, or conjunctiva (xerophthalmia). There are many causes of xerosis, and treatment depends on the particular cause.

Xeroderma pigmentosum is a genetic disease characterized by such extraordinary sensitivity to sunlight that it results in the development of skin cancer at a very early age. It is abbreviated as XP. Children with XP disease can only play outdoors safely after nightfall. XP is due to defective repair of damage done to DNA by ultraviolet (UV) light.…

Prefix indicating dryness, as in xeroderma (dry skin).

A surgical graft of tissue from one species to an unlike species (or genus or family). A graft from a baboon to a human is a xenograft. The prefix “xeno-” means foreign. It comes from the Greek word “xenos” meaning stranger, guest, or host. (Xeno- and xen- are variant forms of the same prefix.)