Leprosy and psoriasis are unrelated conditions - apart from both affecting the skin.
Psoriasis is in fact a relatively common condition worldwide ( affecting at least 2% of males and females in UK and also the Philippines ). Psoriasis is not an infection, but a chronic overproduction of skin cells ( resulting in crusty and flaking patches often on elbows, knees, scalp and lower back ). It’s probably the result of over-production of " messenger " proteins by the immune system. It may be complicated by joint inflammation ( arthritis ). There’s a range of treatments, depending on areas affected and severity.