> The discovery of new blood types isn't limited to transfusion emergencies. It also sheds light on certain previously unexplained pathologies. The specialist discusses the recent case of three siblings who had suffered from mysterious rheumatological disorders since adolescence. It was only after identifying their rare blood type that doctors were able to establish a probable link with their symptoms.

How does that work? Were all three siblings regularly receiving donated blood? The article doesn't expand on this at all.

I read it to mean that the rheumatological symptoms they had were the result of their unusual blood type. Hard to say without more info, but something about that particular blood type could be linked to an inflammatory disorder.