What Causes A Painful Spot On Penis?

can you get icthyosis on the penis? I am 30 year old male, 190 lbs., 6'2". I have asthma(mild) and have had it since birth. I have no other skin problems. I have one spot on my penis for the last 10 years. Every doctor has said it is eczema. But no treatment has helped. It is about the size of a dime to a nickel. Sometimes painful and itchy.