[Elderly-onset rheumatoid arthritis distinguished from polymyalgia rheumatica with malignancy]

Area of Science:

• Rheumatology
• Oncology
• Radiology

Background:

• Polymyalgia rheumatica (PMR) and elderly-onset rheumatoid arthritis (EORA) present similar initial symptoms, complicating differential diagnosis.
• Early diagnosis is crucial for effective treatment and preventing long-term joint damage.

Observation:

• A 77-year-old woman presented with shoulder and hip pain and stiffness, initially suspected as PMR.
• Initial tests for rheumatoid factor and anti-cyclic citrullinated peptide antibody were negative, and radiographic findings were inconclusive for rheumatoid arthritis.
• Prednisolone treatment temporarily relieved symptoms and normalized inflammatory markers (erythrocyte sedimentation rate and C-reactive protein), further suggesting PMR.

Findings:

• Computed tomography revealed a lung nodule, later diagnosed as lung cancer.
• Positron-emission tomography showed increased 18F-fluorodeoxyglucose uptake in bilateral shoulder and wrist joints.
• Enhanced MRI and radiography confirmed synovitis and bone erosions, leading to a diagnosis of EORA.

Implications:

• This case underscores the importance of comprehensive evaluation, including advanced imaging and biopsy, in differentiating EORA from PMR, especially when malignancy is suspected.
• Routine evaluation for rheumatoid synovitis is recommended in patients initially diagnosed with PMR.
• Integrated diagnostic approaches combining rheumatological and oncological assessments are vital for complex elderly-onset inflammatory conditions.