Differential Diagnosis for 35-year-old Female with Polyarthralgia and Positive ANA
Single Most Likely Diagnosis
- Systemic Lupus Erythematosus (SLE): The patient's symptoms of polyarthralgia, fatigue, and positive ANA with a titer of 1:160, along with the presence of a nummular dermatitis rash, are consistent with SLE. Although the Smith and SSA/SSB antibodies are negative, they are not required for the diagnosis of SLE.
Other Likely Diagnoses
- Rheumatoid Arthritis (RA): The patient's polyarthralgia affecting multiple joints, including the elbows, wrists, knees, fingers, and neck, could suggest RA. However, the absence of morning stiffness and the presence of a positive ANA might lean more towards SLE or another connective tissue disease.
- Mixed Connective Tissue Disease (MCTD): This condition overlaps with SLE, RA, and scleroderma, and the patient's symptoms could fit this diagnosis, especially if she has features of multiple connective tissue diseases.
- Sjögren's Syndrome: Although the patient is negative for SSA/SSB antibodies, Sjögren's syndrome can still be considered, especially if she has symptoms of dry eyes or mouth, which are not mentioned.
Do Not Miss Diagnoses
- Hypothyroidism: This condition can cause fatigue, arthralgias, and skin rashes, and a positive ANA can be seen in some cases of autoimmune thyroiditis. It's crucial to rule out hypothyroidism due to its potential to cause significant morbidity if left untreated.
- Vasculitis: Conditions like granulomatosis with polyangiitis or eosinophilic granulomatosis with polyangiitis can present with similar symptoms and require prompt diagnosis and treatment to prevent serious complications.
Rare Diagnoses
- Scleroderma: The patient's symptoms do not strongly suggest scleroderma, but it's a consideration in the differential diagnosis of a patient with a positive ANA and polyarthralgia.
- Polymyositis/Dermatomyositis: These conditions are characterized by muscle weakness and specific skin rashes. While the patient has a rash, its description as nummular dermatitis does not strongly suggest dermatomyositis.
- Undifferentiated Connective Tissue Disease (UCTD): This diagnosis is considered when a patient has features of a connective tissue disease but does not meet the full criteria for a specific disease like SLE, RA, or scleroderma. The patient's presentation could fit UCTD, especially if she does not develop more specific features of another disease over time.