A form of consanguinity. Everyone carries recessive alleles, genes that are generally innocuous in the heterozygous state but that in the company of another gene of the same type are capable of causing disease. We are all genetic reservoirs for genetic disease. Since first cousins share a set of grandparents, for any particular allele (gene) in the father, the chance that the mother inherited the same allele from the same source is 1/8. And for any gene the father passes to his child, the chance is 1/8 that the mother has the same gene and ½ that she transmits it to the child, so 1/8 X ½ = 1/16. A first-cousin marriage therefore has a coefficient of inbreeding of 1/16. The added risks for first cousins depend not only upon this coefficient of inbreeding but also upon their genetic family histories and, in some cases, upon test results (for example, for the risk of beta thalassemia in first cousins of Greek or Italian descent). There are always added risks from the mating of closely related persons.
- Marshall-Smith syndrome
A disorder characterized by advanced bone age at birth, broad forehead, prominent eyes, and small chin. There is difficulty feeding, failure to thrive, retarded psychomotor development, and predisposition to respiratory infection. It may be fatal within the first years of life. The cause of the syndrome is unknown. It is named for Richard E. Marshall […]
- Marx, Gertie F.
Distinguished German-born American physician known as the “mother of obstetric anesthesia.” She almost singlehandedly developed obstetric anesthesiology as a specialty. She advanced the use of epidural injections to ease women’s pain during childbirth. She developed an epidural needle that bears her name and she was the founding editor of Obstetric Anesthesia Digest. Dr. Marx died […]
- MASA syndrome
lumbar lordosis (sway back). MASA is inherited as an X-linked trait and so affects mainly boys. Alternative names for MASA include clasped thumb and mental retardation, congenital clasped thumb with mental retardation, adducted thumb with mental retardation, and the Gareis- Mason syndrome.
- Mask of pregnancy
Muddy-brown pigmentation on the cheeks or elsewhere on the face that develops in about half of all women during pregnancy. Some women also develop it outside pregnancy, as do some women on hormone therapy. The pigmentation is worsened by ultraviolet (UV) light, which tends to darken it. Regular use of a broad-spectrum sunscreen against both […]
- Mask, oxygen
A mask that covers the mouth and nose, and is hooked up to an oxygen tank. It delivers oxygen directly to the patient. Oxygen can also be delivered directly through a nasal catheter, a tube that divides into two smaller tubes that go into the nostrils.