Familial Mediterranean Fever in the First Two Years of Life: A Unique Phenotype of Disease in Evolution

ObjectiveTo characterize the clinical and genetic features of familial Mediterranean fever (FMF).Study designClinical presentation and MEditerranean FeVer mutation type of all patients with FMF, who first manifested the disease at ≤2 years of age were analyzed and compared with patients who first presented with FMF between 2 and 16 years.ResultsOf 814 patients with FMF, in 254 patients (31.2%) the first FMF attack was at ≤2 years of age, with a mean age at onset of 1.1 ± 0.8 years. They were compared with 242 patients who presented with their first manifestation of FMF at 2 to 16 years. The clinical manifestations of FMF were comparable in the 2 patient groups, but the delay of diagnosis was longer in patients with early presentation (3.2 ± 3.2 years vs.1.9 ± 2.7 years in the group with onset at 2-16 years, P < .001). A subgroup of patients (60/254), who were diagnosed at ≤2 years had the highest rate of attacks of fever alone as their sole manifestation (40.0% vs 8.4%, P < .05), and less peritonitis (45% vs 86.1%, P < .05) and pleuritis (3.4% vs 32.9%, P < .05). Most of these patients were homozygous for the M694V mutation and were of North African (Sephardic Jewish) extraction.ConclusionIn early life, FMF often begins with an atypical presentation, characterized by attacks of fever alone, and its diagnosis and initiation of treatment is therefore significantly delayed.