Differential Diagnosis for Back Pain and HLA B27 Positive
Single Most Likely Diagnosis
- Ankylosing Spondylitis (AS): This is the most likely diagnosis given the presence of back pain and a positive HLA B27 test. AS is a form of arthritis that primarily affects the spine, and HLA B27 is a genetic marker strongly associated with the disease.
Other Likely Diagnoses
- Reactive Arthritis: This condition can occur after certain bacterial infections and is also associated with HLA B27 positivity. It often presents with back pain, among other symptoms.
- Psoriatic Arthritis: Although primarily associated with skin psoriasis, some patients with psoriatic arthritis may test positive for HLA B27, and back pain can be a symptom.
- Enteropathic Arthritis: Associated with inflammatory bowel diseases like Crohn's disease and ulcerative colitis, this condition can cause back pain and may be linked to HLA B27 in some cases.
Do Not Miss Diagnoses
- Infectious Spondylodiscitis: Although less likely, an infection of the intervertebral disc space can cause severe back pain and must be considered, especially if there are signs of infection or recent travel/history that might predispose to certain pathogens.
- Spinal Epidural Abscess: A serious condition that requires immediate medical attention, characterized by an abscess in the epidural space surrounding the spinal cord, which can cause back pain among other neurological symptoms.
Rare Diagnoses
- Spondyloarthritis associated with Inflammatory Bowel Disease (IBD): While not as common as other forms of spondyloarthritis, back pain in the context of IBD (like Crohn's disease or ulcerative colitis) and HLA B27 positivity could suggest this diagnosis.
- Juvenile Idiopathic Arthritis (JIA): In younger patients, JIA could be a consideration, especially if there's a history of joint issues and back pain, though HLA B27 is more commonly associated with certain subtypes like enthesitis-related arthritis.
- Undifferentiated Spondyloarthritis: Patients who do not meet the full criteria for a specific type of spondyloarthritis but have chronic back pain and HLA B27 positivity might be classified under this category.