Keratin granulations are spotty white deposits on nails. This superficial disorder is often thought of being a nail fungus, specifically 'white superficial onychomycosis'. Luckily, this is more of a reaction to nail polish and not a fungal infection.
This nail disorder is a result of poor cosmetology work on fingernails and toenails. Keratin is considered non-living tissue, like hair, made of protein. When new nail polish is placed on top of old nail polish that is chipped and uneven, keratin forms due to the chemicals in the nail polish. This happens more often in older women than younger.
If you do not have a fungal infection, then the best treatment is to remove all fingernail polish as well as any false tips, synthetic nails or gel nails. The nails underneath all this will not look healthy at this point, they will be spotty and perhaps discolored. Gentle nail care is needed by way of careful trimming, not pushing cuticles down, and warm oil treatments. These warm oil treatments can consist of not hot, olive oil or other cooking oil in a bowl, then place finger tips in the bowls for 10 minutes to help reduce the brittleness of nails. Consider doing this before bedtime and wearing cotton gloves over top, do this for 7 - 10 days.
Take at look at the discoloured nails page for helpful hints on making your nails look white without polish.