A 66-year-old man with a history of ankylosing spondylitis of long evolution. He presents proteinuria of 6 grams per day with hypoalbuminemia and edema. In the urinary sediment no hematuria is detected. His plasma creatinine is 1.6 mg/dL and his glomerular filtration rate is 45 mL/min. Glycemia 110 mg/dL. His severe spinal deformity makes it difficult to perform percutaneous renal biopsy. What is the correct initial approach?
The correct answer is: 3. Subcutaneous fat biopsy. Lupus erythematosus, some vasculitides, Goodpasture's disease and other systemic diseases (ankylosing spondylitis is one of them) affect the kidney and condition its prognosis. The appearance of urinary abnormalities or renal impairment of parenchymal cause are indications for renal biopsy, even with proteinuria ranges lower than those accepted in primary nephropathies. The determination of anti-GBM antibodies and ANCAS are helpful for diagnosis, but they do not replace renal biopsy, since they lack prognostic value and do not help to plan treatment. In this case, in which we are led to think that renal biopsy is not possible, we must relate AE to renal failure. In most cases, the relationship is established by an IgA nephropathy, which presents with hematuria, a symptom that claims not to exist in this case. A non-negligible number of patients with evolved AD is amyloidosis, which also matches the patient's symptomatology. Therefore, and given that amyloidosis can be diagnosed with a subcutaneous fat biopsy, it is answer 3 that should be considered valid.
To initiate corticoids for suspicion of minimal change glomerular disease.
Treat with cyclophosphamide for suspected membranous glomerulopathy.
Subcutaneous fat biopsy.
Initiate dialysis.
Glucose overload test to rule out diabetic nephropathy.
and given that amyloidosis can be diagnosed with a subcutaneous fat biopsy, it is answer 3 that should be considered valid.