[Arjun]

Pernicious anaemia is an autoimmune disorder in which the gastric mucosa is atrophic with loss of parietal cells causing intrinsic factor deficiency. Intrinsic factor is required for the absorption of Vitamin B12. So in its absence almost NO vitamin B12 gets absorbed. Anti-parietal cell antibodies are present in about 90% of the cases.

The commonest cause of Vitamin B12 deficieny, rather than being dietary is pernicious anaemia, which implies that individuals with pernicious anaemia ultimately develop Vitamin B12 deficiency. Now the symptoms of this Vit. B12 deficiency which has developed secondary to pernicious anaemia are - mild jaundice, lemon yellow tinge to the skin, tongue may be red, smooth and sore and indigestion may be present. In some cases subacute combined degeneration of the spinal cord develops and peripheral neuropathy resulting in an abnormal gait with sensory and motor loss.

The classical description of pernicious anaemia is of an elderly, grey haired, pale person, with lemon yellow skin, a smooth sore tongue and an abnormal gait.

References:
Hutchison's Clinical Methods - Twentieth Edition
Textbook of Pathology by Harsh Mohan