Differential Diagnosis for Elderly Patient with Elevated WBC, Low-Grade Fever, and Arthralgias

Single Most Likely Diagnosis

• Polymyalgia Rheumatica (PMR): This condition is common in the elderly, characterized by elevated WBC, low-grade fever, and arthralgias, particularly affecting the shoulders and hips. The presence of these symptoms in an elderly patient makes PMR a leading consideration.

Other Likely Diagnoses

• Rheumatoid Arthritis (RA): Although it can occur at any age, RA often presents with similar symptoms, including arthralgias and elevated inflammatory markers. The low-grade fever can also be a feature of active RA.
• Osteoarthritis with Infection: While osteoarthritis itself does not typically cause fever or elevated WBC, a superimposed infection (e.g., septic arthritis) could explain these findings, especially if the patient has a history of joint disease.
• Chronic Infections (e.g., Tuberculosis, Endocarditis): These conditions can present with nonspecific symptoms such as low-grade fever, arthralgias, and elevated WBC. Elderly patients may not always exhibit the classic symptoms of these diseases.

Do Not Miss Diagnoses

• Septic Arthritis: This is a medical emergency that requires prompt diagnosis and treatment. Even if less likely, the potential for severe joint damage and systemic infection makes it crucial not to miss.
• Malignancy (e.g., Lymphoma, Leukemia): Certain cancers can present with systemic symptoms like fever, arthralgias, and elevated WBC. Given the potential for rapid progression and the importance of early treatment, malignancy must be considered.
• Giant Cell Arteritis: Similar to PMR, but with a higher risk of complications like visual loss. It often co-exists with PMR and can present with similar symptoms, making it a critical diagnosis not to miss.

Rare Diagnoses

• Relapsing Polychondritis: A rare autoimmune disorder that can cause inflammation of cartilaginous structures, leading to arthralgias, fever, and elevated WBC.
• Adult-Onset Still's Disease: A rare condition characterized by high fevers, salmon-colored rash, and arthralgias, which can be challenging to diagnose due to its rarity and nonspecific symptoms.
• Sarcoidosis: Although more commonly associated with pulmonary symptoms, sarcoidosis can cause arthralgias and fever. It is less common in the elderly but should be considered in the differential diagnosis due to its potential for multi-system involvement.