Association of mastocytosis with inflammatory joint diseases: a series of 31 patients.

OBJECTIVES: We studied the clinical phenotypes and tolerance to treatments in a series of patients affected by both inflammatory joint diseases and mastocytosis.

METHODS: This retrospective multicenter study was conducted on behalf of 3 networks focused on mastocytosis, pediatric, and adults' inflammatory joint diseases. Patients who displayed both mastocytosis and inflammatory joint diseases were included.

RESULTS: A total of 31 patients were included. They had spondyloarthritis (SpA) (16 patients), rheumatoid arthritis (6 patients), juvenile idiopathic arthritis (2 patients), and undifferentiated arthritis (7 patients). The median ages at diagnosis of arthritis and mastocytosis were 44 and 40.5 years, respectively. Disease-modifying anti-rheumatic drugs (DMARDs) were required in 22 patients, comprising mostly methotrexate (13 patients), salazopyrin (8 patients), anti-tumor-necrosis-factor agents (7 patients), and corticosteroids (9 patients). They were well tolerated. Adverse events occurred in 2/24 patients receiving non-steroidal anti-inflammatory drugs. The prevalence of SpA among the 600 patients included in the mastocytosis cohort was 2.33%, which is significantly higher than the prevalence of SpA in the French population (p < 0.001).

CONCLUSIONS: This study suggests that mastocytosis is associated with a higher prevalence of SpA than expected, and that DMARDs, notably anti-TNFα agents, are well tolerated in patients with mastocytosis. Mast cells might be involved in the development of SpA.