Rare systemic causes

• polycythaemia rubra vera - especially following a hot bath
• myeloproliferative diseases e.g. leukaemia, myeloma
• carcinoid syndrome
• haemochromatosis
• brain tumour (particularly invading floor of 4th ventricle)
• drugs - opiates, cocaine, belladonna alkaloids, antidepressants, CNS stimulants, cimeditine, chloroquine and other antimalarials, PUVA
• autoimmune disease - pruritus is an occasional manifestation of systemic lupus erythematous, systemic sclerosis, sicca syndrome
• mastocytosis eg. urticaria of the newborn
• AIDS - pruritus can be seen in around 84% of people with AIDS with or without a rash (1)
• psychiatric

Reference:

• 1. National cancer institute 2008. Pruritus