This has been in progress for over a decade. It's a detailed NPRM that deserves a close read and public comment is due by July 22, 2013:
"SUMMARY: Several body systems in our Listing of Impairments (listings) contain listings for children based on impairment of linear growth or weight loss. We propose to replace those listings with new listings, add a listing to the genitourinary body system for children, and provide new introductory text for each listing explaining how to apply the new criteria. The proposed revisions to our listings reflect our program experience, advances in medical knowledge, comments we received from medical experts and the public at an outreach policy conference, and comments we received in response to a notice of intent to issue regulations and request for comments (request for comments) and an advance notice of proposed rulemaking (ANPRM). . ."