On Mar. 31, 2020, NIH researchers announced they had discovered a second gene that causes melorheostosis, a rare group of conditions involving an often painful and disfiguring overgrowth of bone tissue. The gene, SMAD3, is part of a pathway that regulates cell development and growth. The researchers were working to develop an animal model with a mutant version of SMAD3 to test potential treatments for the condition. The study was published in the Journal of Experimental Medicine.