MEFV and familial Mediterranean fever: A first explanation to the high number of genetically-unexplained patients could very well be clinical misdiagnosis with a disease mimicking FMF and unrelated to MEFV. According to this hypothesis, we could expect the ratio [heterozygous carriers/non carriers] (R) at the MEFV locus to be similar in genetically-unexplained patients and in the general population from the same origin.