Differential Diagnosis for Polyarthralgia with Recurrent Fever
- Single Most Likely Diagnosis
- Adult-Onset Still's Disease (AOSD): Despite initial normal ferritin levels, the recurrent fever, polyarthralgia, and inflammatory changes on biopsy are consistent with AOSD. The absence of hepatosplenomegaly and leukocytosis does not rule out this diagnosis. The high IgG1 level also supports this diagnosis.
- Other Likely Diagnoses
- Systemic Lupus Erythematosus (SLE): Although ANA, anti-ENA, and dsDNA are negative, SLE can present with a wide range of symptoms, including polyarthralgia, fever, and oral ulcers. The presence of immune complex deposition in the kidney biopsy also suggests SLE.
- Relapsing Polychondritis: Although the patient denies redness over auricular cartilages and dorsum of nose, this diagnosis cannot be entirely ruled out. The ground-glass opacities on CT chest and inflammatory changes on biopsy could be consistent with relapsing polychondritis.
- Sjögren's Syndrome: The presence of oral ulcers, sore throat, and nasal ulcer with crusting could suggest Sjögren's syndrome. However, the absence of other characteristic symptoms, such as dry eyes and mouth, makes this diagnosis less likely.
- Do Not Miss Diagnoses
- Infectious Diseases (e.g., Endocarditis, Tuberculosis): Although extensive evaluation for infections has been unremarkable, it is essential to continue monitoring for infectious diseases, as they can present with non-specific symptoms, such as fever and polyarthralgia.
- Lymphoma: The presence of recurrent fever, night sweats, and weight loss (not mentioned, but possible) could suggest lymphoma. Although CT chest shows no lymphadenopathy, lymphoma cannot be entirely ruled out.
- Rare Diagnoses
- Hyper-IgG4 Disease: Although IgG4 level is normal, this disease can present with a wide range of symptoms, including polyarthralgia, fever, and inflammatory changes on biopsy.
- Multicentric Castleman's Disease: This rare disease can present with fever, polyarthralgia, and lymphadenopathy (not present in this case). However, the presence of immune complex deposition in the kidney biopsy could suggest this diagnosis.
- Autoinflammatory Disorders (e.g., TNF-Receptor Associated Periodic Syndrome): These disorders can present with recurrent fever, polyarthralgia, and inflammatory changes on biopsy. However, they are rare and often require specific genetic testing for diagnosis.