Dr. Abigail Waldman, MD FAAD on Instagram: "Idiopathic guttate hypomelanosis is a very common condition that presents on sun exposed areas like arms and legs. It is primarily due to sun damage and aging. The ditterential includes vitiligo and tinea versicolor. A dermatologist should easily be able to distinguish these with exam or some simple testing. While retinoids, glycolic acid and Azelaic acid can help blend the color, there’s no cure for this and the best thing is sun protection for preven