RAB6A and cryopyrin-associated periodic syndrome: Hence, the intracellular accumulation of unprenylated Rab GTPases is highly indicative of MKD, distinguishing it from other IL-1β-mediated diseases such as Cryopyrin-associated periodic syndromes (CAPS) and Familial Mediterranean fever (FMF) (6, 7) that are caused by variants in NLRP3 or MEFV, respectively.