Differential Diagnosis

The patient's presentation of autoimmune urticaria, positive ANA test with high titer and multiple nuclear fluorescence patterns, anemia of chronic inflammation, and various systemic symptoms suggests an underlying autoimmune or rheumatologic condition. Here's a categorized differential diagnosis:

• Single Most Likely Diagnosis

  • Systemic Lupus Erythematosus (SLE): Although specific antibody tests like anti-dsDNA and anti-Smith are negative, the high ANA titer, multiple nuclear fluorescence patterns, and the combination of systemic symptoms such as anemia of chronic inflammation, joint pain, fatigue, and GI symptoms are highly suggestive of SLE. The presence of premature atrial contractions could be related to the systemic inflammation seen in SLE.

• Other Likely Diagnoses

  • Mixed Connective Tissue Disease (MCTD): Given the presence of a high ANA titer with multiple nuclear fluorescence patterns and the combination of symptoms that could suggest overlap with different autoimmune diseases (e.g., lupus, rheumatoid arthritis, scleroderma), MCTD is a consideration, especially if specific antibodies for other diseases are negative.
  • Rheumatoid Arthritis (RA): Although the primary symptoms described don't directly point towards RA, the presence of joint pain and anemia of chronic inflammation could suggest an inflammatory arthritis like RA, especially if there are other signs such as morning stiffness or specific joint involvement not mentioned.
  • Sjögren's Syndrome: This condition can present with systemic symptoms, including fatigue, joint pain, and GI symptoms, along with a positive ANA test. However, the absence of specific symptoms like dry eyes and dry mouth makes this less likely.

• Do Not Miss Diagnoses

  • Cancer-Associated Autoimmune Disorders: Certain cancers can trigger paraneoplastic syndromes that mimic autoimmune diseases. It's crucial to rule out underlying malignancies, especially given the patient's anemia and systemic symptoms.
  • Infectious Diseases (e.g., Endocarditis, Lyme Disease): These conditions can cause systemic symptoms, including joint pain, fatigue, and heart manifestations like premature atrial contractions. They can also trigger autoimmune responses.

• Rare Diagnoses

  • Scleroderma (Systemic Sclerosis): While the described symptoms don't directly suggest scleroderma, the presence of a positive ANA test and systemic symptoms could be seen in this disease, especially if there are skin manifestations not mentioned.
  • Relapsing Polychondritis: This rare autoimmune disorder can cause systemic inflammation, joint pain, and potentially heart issues, although it's more commonly associated with cartilage inflammation.
  • Autoinflammatory Disorders: Conditions like Familial Mediterranean Fever or other periodic fever syndromes could present with recurring episodes of inflammation and systemic symptoms, although they are less likely given the patient's specific presentation.