The aims of this study were to compare demographic data, clinical features, and severity scores of familial Mediterranean fever patients carrying E148Q variant with the patients having homozygous pathogenic MEFV mutations and to evaluate both of these groups for the performance of Tel-Hashomer, Livneh, and pediatric diagnostic criteria.The demographic and clinical data of patients with familial Mediterranean fever either heterozygous or homozygous for E148Q variant (group 1) and patients with homozygous mutations (M694V, M694I, M680I, V726A) (group 2) were collected retrospectively. All patients were evaluated for 3 diagnostic criteria.E148Q variant was present in 128 patients (22.9%), 112 of whom had heterozygous and 16 of whom had homozygous E148Q mutation. Group 2 had 430 patients (77.1%), 372 of whom had homozygous M694V mutation, 50 of whom had homozygous M680I mutation, 5 of whom had homozygous V726A mutation, and 3 of whom had homozygous M694I mutation. Pleuritis, arthritis, recurrent fever, erysipelas-like erythema, and anemia were significantly more common in group 2 than group 1 (p < 0.05). Moderate and severe Pras scores were significantly higher in group 2 (p < 0.001). During attack-free periods, C-reactive protein, erythrocyte sedimentation rate, and serum amyloid A were found significantly higher in group 2 than in group 1 (p < 0.05). The percentage of children diagnosed according to Tel-Hashomer and pediatric criteria was significantly higher in group 2 than in group 1 (p < 0.05). Both groups show similar diagnostic utility by Livneh criteria.Children with the E148Q variant met the 3 diagnostic criteria; they had a milder disease course both clinically and in laboratory means.