FAQ / Resources - Nail Disorders Nails with psoriasis frequently have tiny pits in them. Nails may loosen, thicken, or crumble, and are difficult to treat. Dark streaks or bands on multiple fingernails and toenails in African-Americans are usually normal. They tend to increase in number as a person ages. However, the development of a single dark band on a nail could be a sign of a dangerous type of skin cancer called malignant melanoma and should be checked by your dermatologist.		Did You Know?       Did you know that the most common infection of the nails is caused by a one-cell plant called fungus? Fungal nail infections, or onychomycosis, are more common on the toe nails than the fingernails and affects about 12% of all Americans.               "The world is round and the place which may seem like the end, May also be the beginning."