psoriasis is a skin disease where skin turnover occurs very fast and it piles up to give flaky patches....it can occur on any part of the body but predominantly seen on the extensor aspect of extremities and scalp. many will consider that it's a stubborn dandruff but it could be psoriasis. in some nail changes take place in the form of rough texture of nails and lifting of nail from the bed. some people get joint involvement in the form of painful swollen joints of hands . psoriasis can be exaggerated by mental stress, alcohol consumption, smoking, certain pain killer medication.treatment of psoriasis depends on its extent, associated co morbidities, age etc..its a chronic disease and long term treatment is required