A 38 year old female patient was on Isoniazid therapy for tuberculosis. She developed rashes on the exposed pas of her body. She has disoriented memory. Family members gives history of diarrhea also. What is the diagnosis:

Isoniazid inhibits the endogenous synthesis of niacin. So the patient has developed pellagra i.e. dermatitis, dementia and diarrhea. Prolonged treatment with isoniazid leads to pyridoxine deficiency, which is required for endogenous synthesis of niacin.