Differential Diagnosis
The patient's symptoms and laboratory results suggest an autoimmune or inflammatory condition. Here's a categorized differential diagnosis:
- Single most likely diagnosis
- Polymyalgia Rheumatica (PMR): The patient's symptoms, such as shoulder pain, loss of appetite, and limited range of motion in the shoulder, are relieved by prednisone, which is a common treatment for PMR. The elevated sed rate and monocytosis also support this diagnosis.
- Other Likely diagnoses
- Rheumatoid Arthritis (RA): Although the rheumatoid factor and anti-cyclic citrullinated peptide (CCP) antibodies are negative, the patient's symptoms and elevated sed rate could still be consistent with RA, especially given the response to prednisone.
- Giant Cell Arteritis (GCA): The patient's age and symptoms, such as shoulder pain and limited range of motion, could be consistent with GCA, which is often associated with PMR.
- Do Not Miss
- Lymphoma: The patient's monocytosis and elevated sed rate could be indicative of an underlying lymphoma, which would require prompt diagnosis and treatment.
- Infection: The patient's symptoms and laboratory results could also be consistent with an underlying infection, such as endocarditis or osteomyelitis, which would require prompt diagnosis and treatment.
- Rare diagnoses
- Relapsing Polychondritis: The patient's symptoms, such as shoulder pain and limited range of motion, could be consistent with relapsing polychondritis, a rare autoimmune disorder that affects the cartilage.
- Sjögren's Syndrome: Although the patient's SSA and SSB antibodies are negative, the patient's symptoms, such as dry eyes and mouth, could be consistent with Sjögren's syndrome, a rare autoimmune disorder that affects the exocrine glands.