Hi, You are having hypermelanosis on arm and back. There are many causes of hypermelanosis. It may be hereditary, vitamin deficiencies,anaemia, stress, enviormental, pollution ,sun rays, endocrinal disorders,D M, renal diseases or other internal diseases, HIV,malignancies, drugs..etc Blood,sonogrphic and radiologic investigations may be done to find out the cause. It may be without cause. Tablets containing vitamin C,nicotinic acid snd glutathion may improve the disease. Local application of kojic acid and vitamin C may be helpful. You consult dermatologist for perfect diagnosis and treatment. There is urinary complaints also, you consult urologist too. I hope you got my answer. Thanks. Dr. Ilyas Patel MD