Differential Diagnosis for Leg Weakness and High ESR

Single Most Likely Diagnosis

• Polymyalgia Rheumatica (PMR): This condition is characterized by muscle pain and stiffness, particularly in the shoulders and hips, but can also cause leg weakness. A high ESR (erythrocyte sedimentation rate) is a hallmark of PMR, making it a likely diagnosis given the symptoms.

Other Likely Diagnoses

• Rheumatoid Arthritis (RA): While RA primarily affects the hands and feet, it can cause widespread weakness, including in the legs. High ESR is common in RA due to the inflammatory nature of the disease.
• Lupus: Systemic lupus erythematosus can cause a wide range of symptoms, including muscle weakness and high ESR due to its autoimmune and inflammatory characteristics.
• Osteoarthritis with significant inflammation: Though less common, severe osteoarthritis can lead to significant inflammation, resulting in a high ESR and potentially causing leg weakness due to pain and decreased mobility.

Do Not Miss Diagnoses

• Giant Cell Arteritis (GCA): A form of vasculitis that can lead to blindness and other serious complications if not promptly treated. It often presents with high ESR and can be associated with PMR, making it crucial not to miss, especially in older adults.
• Multiple Myeloma: A type of blood cancer that can cause bone pain, weakness, and elevated ESR. It's less common but critical to diagnose early due to its potential for severe outcomes.
• Spinal Stenosis or Cord Compression: Conditions that can cause leg weakness due to compression of the spinal cord or nerves. While ESR might not be directly elevated due to these conditions, they are critical to identify due to the potential for irreversible neurological damage.

Rare Diagnoses

• Dermatomyositis: An inflammatory disease characterized by skin rash and muscle weakness. It can cause leg weakness and has an elevated ESR due to inflammation.
• Inclusion Body Myositis: A progressive muscle disorder that can cause leg weakness. It's less common and might not always present with a significantly elevated ESR but is important to consider in the differential diagnosis of leg weakness.
• Vasculitis (e.g., ANCA-associated vasculitis): Conditions that involve inflammation of the blood vessels and can cause a wide range of symptoms, including leg weakness and elevated ESR. They are less common but can be severe and require prompt treatment.