Differential Diagnosis
The patient's symptoms and laboratory results suggest an autoimmune disorder. Here's a categorized differential diagnosis:
- Single most likely diagnosis
- Systemic Lupus Erythematosus (SLE): The patient's positive ANA (1:640 homogenous and 1:1280 dense fine speckled), low C4, intermittent leukopenia, and positive anti-SSA/Ro-70 antibodies are all consistent with SLE. The episodes of color changes in her feet, possibly related to cold or pressure, could be a manifestation of Raynaud's phenomenon, which is common in SLE.
- Other Likely diagnoses
- Raynaud's phenomenon: Although this could be a part of SLE, it's also possible for Raynaud's to occur independently. The patient's symptoms of color changes in response to cold and pressure are classic for this condition.
- Mixed Connective Tissue Disease (MCTD): Given the presence of anti-SSA/Ro-70 antibodies and the patient's other symptoms, MCTD is a consideration, although the lack of specific symptoms like arthralgias, myalgias, or esophageal dysmotility makes it less likely.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Cryoglobulinemia: This condition can cause cold-induced vasculitis and should be considered, especially given the patient's hives and cold-induced symptoms. However, the normal video capillaroscopy and lack of other specific symptoms make it less likely.
- Antiphospholipid Syndrome (APS): Although the patient's symptoms don't strongly suggest APS, the presence of a positive ANA and low C4 warrants consideration of this condition, which can cause thrombosis and other serious complications.
- Rare diagnoses
- Erythromelalgia: This rare condition causes burning pain, heat, and redness in the hands and feet, often in response to warmth. While the patient's symptoms are somewhat different, erythromelalgia could be considered, especially if other diagnoses are ruled out.
- Chilblain lupus: A rare form of cutaneous lupus that causes cold-induced lesions, which might fit the patient's symptoms of cold-induced color changes and hives. However, the lack of specific skin lesions and other symptoms makes this diagnosis less likely.