Rare Disease Can Be Misdiagnosed as Rheumatoid Arthritis

Whipple’s disease (WD) is a rare disease that predominantly affects middle-aged white men, and its diagnosis is often delayed because it is misdiagnosed as rheumatoid arthritis (RA). A new study in Orphanet Journal of Rare Diseases aimed to describe clinical symptoms of WD and appropriate treatment.

Researchers identified 7 patients who had been misdiagnosed with RA. The median time from onset of symptoms to the diagnosis of WD was 5 years. During that time, all but 1 patient received immunosuppressive treatment. However, WD is a chronic infectious disorder caused by Tropheryma whipplei (TW) and should be treated with antibiotics.

“Without antibiotic treatment the natural course of WD may be fatal; erroneously induced immunosuppressive treatment may even accelerate the clinical progression of the disease,” the authors wrote.

Following the diagnosis of WD, all patients were initiated on antibiotic treatment.

The researchers determined that the diagnosis of RA was likely made because the patients “suffered from joint manifestations mimicking seronegative RA,” plus the course of the disease involved the small joints in all patients and joint erosions in 3 of the patients. Joint manifestations of WD infrequently involve the small joints.

“The fact that bone erosions of the small joints are rather characteristic for RA and are part of the 1987 ACR-classification criteria for RA might have led to the wrong diagnosis in the reported patients,” the authors wrote.

Establishing a diagnosis of WD requires TW-polymerase chain reaction testing of synovial fluid to distinguish the infection from RA, and the authors recommend reevaluating seronegative RA patients with prolonged disease course and insufficient treatment response.

“… it is possible that destructive arthritis is misinterpreted even by radiologists and that a wrong interpretation of radiographs may lead to the wrong diagnoses,” the authors wrote. “Thus, both rheumatologists and radiologists should increase their awareness for rare diseases like WD as a reason for erosive bone changes.”