Rheumatoid Arthritis Masquerading as Fibromyalgia

Area of Science:

• Rheumatology
• Medical Imaging
• Immunology

Background:

• Inflammatory arthritis, like rheumatoid arthritis (RA), shares symptoms with fibromyalgia syndrome (FMS).
• Distinguishing low-intensity, antibody-negative RA from FMS is diagnostically challenging.
• Coexistence of RA and FMS further complicates accurate diagnosis.

Observation:

• A middle-aged woman with a 4-year history of suspected FMS, osteoarthritis, and osteoporosis was evaluated.
• Musculoskeletal ultrasound (MSKUS) was employed for diagnostic assessment.
• The patient was ultimately diagnosed with seronegative RA.

Findings:

• Musculoskeletal ultrasound (MSKUS) identified features indicative of low-intensity inflammatory arthritis.
• Targeted therapy with etanercept resulted in a complete clinical response.
• C-reactive protein levels normalized following treatment.

Implications:

• MSKUS is a sensitive imaging modality for differentiating seronegative RA from FMS.
• Accurate diagnosis via MSKUS enables appropriate and effective targeted therapy.
• This approach has significant clinical implications for managing patients with overlapping rheumatological conditions.