Differential Diagnosis
- Single most likely diagnosis + Lupus nephritis flare: This patient has a history of systemic lupus erythematosus (SLE) and presents with symptoms and laboratory results consistent with a lupus nephritis flare, including joint pain, swelling, proteinuria, hematuria (RBC casts), and elevated serum creatinine. The patient's decision to stop hydroxychloroquine prior to conception may have contributed to the flare.
- Other Likely diagnoses + Preeclampsia: The patient's elevated blood pressure, proteinuria, and edema are consistent with preeclampsia. However, the presence of RBC casts and the patient's history of SLE make lupus nephritis flare more likely. + Chronic hypertension with superimposed preeclampsia: This diagnosis is possible, given the patient's elevated blood pressure and proteinuria. However, the patient's history and laboratory results are more consistent with a lupus nephritis flare.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.) + HELLP syndrome: Although the patient's laboratory results do not show the typical findings of HELLP syndrome (hemolysis, elevated liver enzymes, and low platelet count), the patient's platelet count is low, and the diagnosis should be considered due to its high morbidity and mortality. + Thrombotic thrombocytopenic purpura (TTP): This rare disorder can present with thrombocytopenia, hemolytic anemia, and renal failure, making it a diagnosis that should not be missed.
- Rare diagnoses + Poststreptococcal glomerulonephritis: This diagnosis is unlikely, given the patient's history and laboratory results, but could be considered if other diagnoses are ruled out. + Vasculitis (e.g., ANCA-associated vasculitis): This diagnosis is possible, given the patient's history of SLE and the presence of RBC casts, but is less likely than a lupus nephritis flare.