Fibromyalgia
The most likely diagnosis is fibromyalgia, based on the characteristic presentation of chronic widespread pain, multiple tender points at classic anatomic sites, absence of inflammatory markers, normal imaging, and associated symptoms of poor sleep and chronic pain without objective joint inflammation. 1, 2
Clinical Features Supporting Fibromyalgia
This patient demonstrates the hallmark features of fibromyalgia:
Widespread pain involving "all" joints without objective swelling, redness, or stiffness - this diffuse, non-anatomic pain pattern is characteristic of central pain processing disorders rather than inflammatory arthritis 3, 4
Multiple tender points at classic fibromyalgia sites: The patient has documented tenderness at bilateral suboccipital insertions, C5, lateral epicondyles, upper outer buttock quadrants, medial knee fat pads, and second rib - these correspond to the traditional 18 tender point sites used in fibromyalgia diagnosis 1, 5
Associated symptoms of poor sleep quality and chronic pain - sleep disturbance is a core feature of fibromyalgia and contributes to the pain amplification 1, 4
History of chronic tension headaches - fibromyalgia commonly coexists with other functional pain syndromes including chronic headaches 4
Numbness in fingers and toes (paresthesias) - this is a recognized symptom of fibromyalgia, not indicative of neuropathy in this context 1
Failure to respond to NSAIDs - fibromyalgia represents central pain processing dysfunction and does not respond to anti-inflammatory medications, unlike peripheral inflammatory conditions 3
Laboratory and Imaging Findings
The diagnostic workup effectively excludes inflammatory and autoimmune conditions:
Normal ESR (12) - this low inflammatory marker argues strongly against inflammatory arthritis such as rheumatoid arthritis or polymyalgia rheumatica 6
Low-titer ANA (1:40 speckled) - this is within normal limits for the general population and not clinically significant; up to 30% of healthy individuals have low-titer ANA 7
Negative rheumatoid factor - excludes rheumatoid arthritis 6
Normal radiographs - absence of erosions, joint space narrowing, or other structural changes excludes osteoarthritis and inflammatory arthropathies 6
Critical Diagnostic Considerations
The HLA-B27 positivity is a red herring in this case - while present in 6-8% of the general population, this patient lacks the clinical features of spondyloarthritis (no axial symptoms, no inflammatory back pain, no morning stiffness, no enthesitis, normal spine radiographs) 6
Fibromyalgia is specifically listed as a disease mimic that can be confused with inflammatory arthritis - EULAR guidelines emphasize that fibromyalgia may coexist with or be misdiagnosed as rheumatoid arthritis, particularly when composite disease activity indices are used 6
The absence of objective joint inflammation on examination is key - the patient has full range of motion without swelling or inflammatory signs, distinguishing this from true inflammatory arthritis 1, 2
Diagnostic Criteria Met
This patient meets the clinical diagnosis of fibromyalgia:
Chronic widespread pain for >3 months affecting multiple body regions 1, 2
Multiple tender points on examination at characteristic anatomic sites 1, 5
Absence of alternative explanation - inflammatory markers normal, imaging normal, no evidence of systemic autoimmune disease 2
Associated symptoms including sleep disturbance, chronic pain, and paresthesias 1
Why Not Other Diagnoses
Not rheumatoid arthritis: Negative RF, normal ESR, no joint swelling, no morning stiffness, normal radiographs, and failure to respond to NSAIDs 6
Not systemic lupus erythematosus: Low-titer ANA is not diagnostic, lacks other SLE features (no rash, no Raynaud's, normal labs) 6
Not spondyloarthritis: HLA-B27 positive but lacks axial symptoms, inflammatory back pain, enthesitis, or radiographic sacroiliitis 6
Not osteoarthritis: Wrong age and distribution pattern, no Heberden's or Bouchard's nodes, pain not activity-related, normal radiographs 6