Very dark patches, of different sizes in diameter, appear on arm suddenly. May be one large, about 1inch in dia, and 2/3 in smaller dia. Over a period of 4/5 weeks they fade away. Quite like the way a bruise fading away. I get no itchy or other feelings. Generally these have been limited to my fore arms, particularly left arm. It first appeared about 3 years back. In the last 3/4 months their frequency have increased. I am 72 yrs and have generally in good health.