Background The MEFV gene encodes the pyrin protein, which regulates IL-1b and IL-18 production, two cytokines that participate in the innate immune response. Mutations in the MEFV gene are associated with familial Mediterranean fever (FMF), but our group identified these mutations in patients with intermittent hydrarthrosis (IH) and palindromic rheumatism (PR). (1, 2).
Objectives To analyse the clinical usefulness of MEFV gene mutation analysis in patients with undifferentiated arthritis (UA).
Methods Descriptive, retrospective study including patients with UA who underwent systematic screening for MEFV gene mutations, and were followed at the Rheumatology Department, Hospital Clínic, Barcelona, between 2000 to 2014. The following clinical and demographic data were collected; age, sex, age at onset of disease, disease duration, joint swelling characteristics: frequency, duration, number of joints involved (monoarthritis, oligoarthritis or polyarthritis), location pattern (upper or lower extremities); seropositivity (rheumatoid factor and/or ACPA), final diagnosis and clinical response to colchicine.
Results Ninety five patients were included (68% female, mean age 39.9±14.7 years, follow up 8.5±6 years). MEFV gene mutational analysis was positive in 21 patients (22%) and negative in 74 (78%).
In patients with mutations, the duration of arthritis was <7 days in 72% patients; 86% had intermittent arthritis, frequently oligoarticular (53%) and commonly affecting the lower extremities (48%). The final diagnosis was: FMF (29%), IH (14%), RA (10%), PR (10%), PsA (10%), Behçet (5%), self-limited arthralgia (10%) and undifferentiated oligoarthritis (5%). 29% patients were RF and/or ACPA positive. 71% patients were treated with colchicine, of whom 86% had a good response.
In patients without mutations, the duration of arthritis was <7 days in 63% patients; 76% had intermittent arthritis, 39% oligoarthritis, and lower extremities were involved in only 28%. The final diagnosis was: RA (22%), PR (22%), Behçet (7%), undifferentiated oligoarthritis (7%) and FMF (3%). 31% patients were RF and/or ACPA positive. Two patients with a diagnosis of FMF had a negative mutational analysis and had a good response to colchicine.
Conclusions MEFV gene mutational analysis may be useful in the differential diagnosis of patients with undifferentiated arthritis, especially those with <7 days of duration, intermittent flares and involvement of the lower extremities. However, due to the difficulty in carrying out mutational analysis and the relatively low percentage of patients with mutations (22%) observed in our cohort, we recommend starting with a therapeutic strategy with colchicine in suspected patients, with only patients with a good clinical response being analysed for the MEFV gene mutation.
Cañete JD, et al. Arthritis Rheum 2006;54:20:2334–2337.
Cañete JD, et al. Arthritis Rheum. 2007;56:2784–2788.
Disclosure of Interest None declared