Porphyria in the Paget family

Has anyone any knowledge of Porphyria in the Paget family of recent years? It started with Mary Queen of Scots, or her father, and has been consistently appearing in the royal families of England ever since. Because of inter marriage it also appeared in the European and Russian royal families. My sister died of Acute Intermittent Porphyria in 1970 and it is only recently, with the advent of technology and DNA that I am able to start my search into my own family tree.  Thank you in advance of any help. Ric Bennett