Bma Illustrated Medical Dictionary

macro-A prefix meaning large, as in

macrophage (a large cell in the immune

system) or macroglossia.

macrobioticsA dietary system in which

foods with a balance of yin and yang

are eaten. Foods are classified as yin or

yang depending on factors such as

their colour, texture, and taste.

macroglossiaAbnormal enlargement of

the tongue. Macroglossia is a feature

of Down’s syndrome, hypothyroidism,

and acromegaly. It is also caused by

some tumours of the tongue, such as a

haemangiomaor a lymphangioma.

macrolide drugsA class of antibiotic

drugsused to treat a wide range of infec-

tions including those of the ear, nose,

throat, respiratory and gastrointestinal

tracts, and skin. Common macrolides

include azithromycinand erythromycin.

macrophageA cell in the immune sys-

tem. Macrophages are large phagocytes,

which can engulf and destroy micro-

organisms and other foreign particles.

They are found in most body tissues.

maculaThe area of the eye’s retina

responsible for seeing fine detail. The

macula surrounds the fovea, which con-

tains the highest density of visual cells.

macular degenerationA progressive,

painless disorder affecting the macula.

The result is a roughly circular area of

blindness that increases in size until it

is large enough to obscure 2 or 3 words

at reading distance. Macular degenera-

tion does not cause total blindness as

vision is retained around the edges of

the visual fields. This condition is a

common disorder in elderly people.

Of the 2 types of macular degenera-

tion that may occur, one type is usually

remedied by laser treatment. There is no

treatment for the other form, although

the affected person may benefit from

aids such as magnifying instruments.

maculeA spot that is level with the

skin’s surface and discernible only by

difference in colour or texture.

mad cow diseaseThe commonly used

name for bovine spongiform enceph-

alopathy(BSE).

magnesiumAn element essential in

the diet for the formation of bones and

teeth, muscle contraction, nerve impulse

transmission, and activation of many

enzymes. Dietary sources include cere-

als, nuts, soya beans, milk, and fish.

magnesium sulphateA magnesium

compound used as a laxative drug and

an anticonvulsant drug.

magnesium trisilicateA magnesium

compound used in antacid drugs.

magnetic resonance imagingSee

MRI.

malabsorptionImpaired absorption of

nutrients by the lining of the small

intestine. Malabsorption may be caused

by many conditions, including lactase

deficiency, cystic fibrosis, chronic pan-

creatitis, coeliac disease, Crohn’s disease,

amyloidosis, giardiasis, Whipple’s dis-

ease, and lymphoma. The removal of

some of the small intestine, and certain

operations on the stomach, may also

result in malabsorption.

Common symptoms are diarrhoea and

weight loss; and in severe cases, there

may also be malnutrition (see nutritional

disorders), vitamin deficiency, mineral

deficiency, or anaemia. Diagnosis may

be made by tests on faeces, blood tests,

barium X-ray examinationand jejunal

biopsy. In most cases, dietary modifica-

tions or supplements are successful in

MACRO- MALABSORPTION

M

MACULA

Retina

Optic

Cornea nerve

Fovea

Lens Macula

M

Iris