Differential Diagnosis for the 81-year-old Woman with Abrupt Onset of Lower Extremity Edema
- Single most likely diagnosis
- D. Minimal change glomerulopathy: This condition is characterized by the sudden onset of nephrotic syndrome, which includes heavy proteinuria (as indicated by 4+ protein on urinalysis), hypoalbuminemia (albumin 1.6 g/dL), and edema. The rapid decline in renal function (creatinine 2.8 mg/dL from 0.7 mg/dL two months prior) could be secondary to minimal change disease or another process, but the presence of nephrotic syndrome points towards a glomerular disease. Minimal change disease is more common in children but can occur in adults, often presenting with nephrotic syndrome.
- Other Likely diagnoses
- C. Membranous nephropathy: This is another cause of nephrotic syndrome in adults, characterized by the deposition of immune complexes on the glomerular basement membrane. It could explain the heavy proteinuria and hypoalbuminemia. However, it typically has a more gradual onset and may be associated with other systemic diseases or infections.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- A. ANCA-associated glomerulonephritis: Although less likely given the presentation with nephrotic syndrome rather than a nephritic picture (which would include hematuria and hypertension), ANCA-associated vasculitis can cause rapid deterioration of renal function and should be considered, especially if there are other systemic symptoms.
- B. Anti–glomerular basement membrane antibody disease: This condition, also known as Goodpasture's syndrome, typically presents with a nephritic picture (hematuria, hypertension) and pulmonary hemorrhage, which is not seen in this patient. However, it's a critical diagnosis to consider due to its severity and the need for prompt treatment.
- Rare diagnoses
- Other rare causes of nephrotic syndrome, such as focal segmental glomerulosclerosis (FSGS), amyloidosis, or light-chain deposition disease, could be considered but are less likely given the acute onset and the absence of other specific findings that might point towards these diagnoses.
The justification for each category is based on the combination of clinical presentation (sudden onset of generalized edema, nephrotic syndrome), laboratory findings (heavy proteinuria, hypoalbuminemia, elevated creatinine), and the absence of specific findings that would point towards other diagnoses (e.g., hematuria, hypertension, or pulmonary symptoms).