Conditions

Small stones made of calcium salts can build up inside the salivary glands and the ducts that drain them.

In sarcoidosis the immune system starts gathering dense clusters of cells, called granulomas, in the tissues.

Scabies is an infestation of the skin by a microscopic mite that burrows into the surface layer.

Scarlet fever is a throat infection caused by group A streptococcus, with a characteristic rash added on top.

A scar is new tissue the body makes to close a wound. It is never identical to the original skin: it has no follicles or glands and its collagen is organised…

Schistosomiasis is caused by tiny worms that live in fresh water in warm countries. There is only one way to catch it: by being in that water.

Sciatica is pain that runs from the lower back or the buttock down the leg because the sciatic nerve is irritated or compressed.

The word "scleroderma" literally means "hard skin", and it is used for two very different things.

In scoliosis the spine does not simply lean sideways: it also rotates around its own axis.

Scurvy is a severe, long-standing lack of vitamin C. Most people think of it as the sailors' disease from old books, and that is exactly why it gets missed…