OBJECTIVES: The diagnosis of familial Mediterranean fever (FMF) can be missed or delayed even in countries where FMF prevalence is high. In this study we investigated the presentation pattern, the frequency of misdiagnosis and the duration of diagnostic delay and its underlying causes in a large cohort followed by a single tertiary centre in Turkey. METHODS: We studied 197 (118 F, 79 M) consecutive patients with FMF (median age: 34 years [IQR: 27-44]). The median registry year of the patients was 2006 [IQR: 2001-2011]. A standardised questionnaire was used to assess age at first symptom, date at diagnosis, previous diagnosis and treatments before the FMF diagnosis. RESULTS: A total of 167 (84%) patients were misdiagnosed and 56 (28%) underwent surgical operations before FMF diagnosis. The most common mis-diagnoses were appendicitis (55%) and acute rheumatic fever (ARF) (45%). The median duration of diagnostic delay was 11 years. Joint attacks were observed to start at a significantly younger age (median age: 3 years) than abdominal attacks (median age: 12 years). Early onset with solo joint attacks, without usual peritonitis attacks and being a carrier of M694V were found to be significantly associated with ARF misdiagnosis. CONCLUSIONS: Misdiagnosis frequency is still significantly high and diagnostic delay is long even in a cohort of patients registered after year 2000 in Turkey. Atypical presentation with solo joint attacks, especially among patients with early onset, seems to play a significant role in misdiagnosis and delay in diagnosis.