The high prevalence of Whipple's disease in patients with inflammatory rheumatic diseases

OBJECTIVES: Whipple's disease (WD) is a rare systemic chronic infection with a large diagnostic delay that favours immunomediated complications. Rheumatological symptoms mimicking rheumatological conditions (RC) usually appear first. However, prevalence of WD among patients with RC is still unknown, therefore, we aimed to study the prevalence of WD in a rheumatological setting and identify clinical/laboratory parameters that detect RC patients at high risk of WD. METHODS: Data of 23,094 patients attending a rheumatological outpatient clinic between 6/2019 and 8/2023 were retrospectively analysed. Clinical features of WD patients in this cohort were compared with a separate retrospective cohort of 55 WD patients for validation. RESULTS: Due to unsatisfactory response to disease-modifying anti-rheumatic drugs (DMARDs) and/or development of gastrointestinal/systemic symptoms, 38 patients were referred for duodenal biopsy and WD was diagnosed in 6/38. Thus, prevalence of WD was 6/23,094 (0.03%, 95% CI 0.01-0.06%). Considering patients with a clinical suspicion of WD, prevalence rose to 6/38 (15.78%, 95% CI 6.02-31.25%), and over 20% in males (5/21, 23.81%, 95% CI 8.22-47.2%). Interestingly, at diagnosis, erythrocyte sedimentation rate and C-reactive protein were elevated in all patients with WD. This finding was confirmed in the separate cohort of 55 patients with WD. CONCLUSIONS: WD is rare but in a rheumatological setting its prevalence is much higher than expected. Physicians should be aware of this condition and investigate its presence to reduce diagnostic delay, unnecessary DMARDs and risk of complications. Correct interpretation of clinical picture, including erythrocyte sedimentation rate and C-reactive protein, is the key to reach this diagnosis.