Differential Diagnosis

The patient's presentation is complex, involving multiple systems and symptoms. Here's a breakdown of potential diagnoses based on the provided information:

• Single Most Likely Diagnosis

  • Ankylosing Spondylitis (AS): The patient's symptoms of polyarthritis with significant spinal involvement, stiff back, and a family history of stiff back (suggestive of a possible genetic predisposition, given the HLA-B27 association) point towards AS. Although HLA-B27 is negative, it's worth noting that not all AS patients are HLA-B27 positive, especially in non-Caucasian populations. The presence of other symptoms like recurrent urethritis/UTI and the specific pattern of arthritis also align with reactive arthritis or other spondyloarthropathies, but AS remains a strong consideration given the spinal predominance and family history.

• Other Likely Diagnoses

  • Reactive Arthritis: Given the patient's history of recurrent urethritis/UTI and the development of arthritis, reactive arthritis is a consideration. It often follows a gastrointestinal or genitourinary infection and can present with asymmetric oligoarthritis, enthesitis, and conjunctivitis, among other symptoms.
  • Psoriatic Arthritis: Although not directly mentioned, the presence of polyarthritis, potential for eye involvement (uniocular proptosis and optic neuritis), and the absence of clear psoriasis could still suggest psoriatic arthritis, especially if there's a family history of psoriasis or if the patient has other psoriatic manifestations not yet identified.
  • Inflammatory Bowel Disease (IBD): The patient's loose stools after NSAIDs could indicate an underlying IBD, which can also cause arthritis, eye inflammation, and other systemic symptoms.

• Do Not Miss Diagnoses

  • Lupus: Despite a negative ANA profile, lupus can sometimes present with atypical features and negative autoantibodies. The photosensitivity, potential renal involvement (recurrent UTIs), and other systemic symptoms warrant keeping lupus in mind, although it seems less likely given the negative ANA and specific pattern of joint involvement.
  • Multiple Sclerosis (MS): The optic neuritis is a red flag for MS, an autoimmune disease that affects the brain and spinal cord. Although the patient's other symptoms don't strongly suggest MS, optic neuritis is a common presenting feature, and missing MS could have significant implications for the patient's prognosis and treatment.

• Rare Diagnoses

  • Relapsing Polychondritis: This rare autoimmune disorder involves cartilage and could explain some of the patient's symptoms, including eye involvement (uniocular proptosis) and potential for arthritis. However, it's less likely given the lack of specific symptoms like cartilage destruction or respiratory involvement.
  • Sarcoidosis: Although less likely, sarcoidosis can cause a wide range of symptoms including arthritis, eye involvement, and potentially some gastrointestinal symptoms. The absence of clear pulmonary symptoms or lymphadenopathy makes this less likely, but it remains a consideration in complex, multisystem diseases.