Which condition, also known as icterus, causes a yellowing of your skin and the whites of your eyes?

Correct — D. Jaundice, whose medical name is icterus, is the yellow discolouration of the skin, the mucous membranes and the sclera — the whites of the eyes.

It appears when bilirubin, the yellow pigment left over when red blood cells are broken down, builds up in the blood because the liver cannot process or excrete it fast enough.

Jaundice is a sign, not a disease in itself. Hepatitis, a blocked bile duct or excessive destruction of red cells can each produce it.

Why the others are wrong

• (a)
  Pemphigus — Pemphigus is a group of autoimmune conditions in which blisters form on the skin and mucous membranes. No bilirubin is involved and the sclera is not coloured.
• (b)
  Ichthyosis — Ichthyosis is a group of inherited disorders leaving dry, thickened, scaly skin. The change is in texture, not colour, and the eyes are unaffected.
• (c)
  Eczema — Eczema, or atopic dermatitis, produces itchy, inflamed and often reddened patches of skin. Redness and irritation, not yellowing, are its signature.

Worn-out red blood cells are broken down, and the haem in their haemoglobin is converted to bilirubin.

The liver conjugates that bilirubin and excretes it in bile, which then leaves the body through the gut.

If red cells are destroyed too fast, if liver cells are damaged, or if the bile duct is blocked, bilirubin backs up into the blood and stains the tissues yellow.

Those three cases are called pre-hepatic, hepatic and post-hepatic jaundice.

The eyes are checked first because the colour shows earliest against the white sclera.

Key facts

• Icterus is the medical term for jaundice, the yellowing of the skin, mucous membranes and sclera.
• Jaundice is caused by an excess of bilirubin, the pigment formed when haemoglobin from red blood cells is broken down.
• Bilirubin is processed by the liver and excreted in bile.
• Jaundice is classified as pre-hepatic, hepatic or post-hepatic according to where the process fails.

Common traps

• Picking a skin disease because the question mentions skin — only jaundice also yellows the whites of the eyes.
• Calling jaundice a disease in its own right — it is a clinical sign with several different underlying causes.

No directly related past PYQ was found.