I'm a medical student and I cannot figure out what is going on with my husband's skin. He has several (20 and counting) subcutaneous nodules on various parts of his body. They are mostly located on his forearms, over his ribs on his anterior chest wall, and on his ischial tuberosities on his buttocks. Most of them are subcentimeter, but one on his ischial prominence is 2.5 cm. He had an excisional biopsy of a couple that overlie his ribs, and they were determined to pathologically be consistent with ganglion cysts. These nodules have since regrown, and every few years he notices new ones appearing, mostly in areas that are pressure points (e.g. from his wristwatch) or where he bumped himself and had a bruise.
Any idea why he's forming these?