VA AM Report 4.11.17- Uric acid nephropathy

Fun report today, two interesting caselets but we’ll focus in on this interesting clinical entity.

#Chronic uric acid nephropathy: So called “gouty kidney” or “gouty nephropathy,” LT informed us the term comes from older autopsy studies noting this finding in a fair number of people, with or without elevated serum uric acid levels. In fact, there is poor correlation between serum uric acid and the incidence of uric acid nephropathy, food for thought considering we treat to serum levels and rarely if ever check urine levels. Still, it will mostly likely be found in a living person in those with severe tophaceous gout and high serum levels, as in our patient this morning.

Histologically, one sees crystalline deposits of uric acid and urate salts in the actual kidney parenchyma and interstitium, so while renal stones from uric acid can cause what we typically think of, tubular obstruction and necrosis, gouty neprhopthy is actually more of a chronic interstitial nephritis, with lymphocytic infiltrates present and evenutally diffuse fibrosis. It typically progresses insidiously, and will not reflect changes in eGFR until later stages of disease. Allopurinol may help with stone formation, as will simple bicarb supplementation to alkalinize the urine, but do not appear to hold off the progression of uric acid nephropathy.

#Tafro syndrome: You know it’s getting real when we talk about multicentric Castleman’s disease. TAFRO syndrome is an acronymous (I just invented that word, you’re welcome) entity characterized by thrombocytopenia, ascites and anasarca, pleural effusions, anemia (microcytic), fever, myelofibrosis, renal failure, and organomegaly. It’s mediated through IL-6 and is responsive to our favorite IL6 inhibitor tocilizumab. Our case was a man with myelofibrosis, a big spleen, and renal failure, but had a positive jak2 and carried a dx of myelofibrosis. Save it for the next time you’re the discussant for a CPS case. Thanks to Rabih for the pearl.

#Fun fact about myelofibrosis from LT and Dr. Buck Strewler: In the “olden days,” (LT’s words), patients with myelofibrosis and high PMN counts were used as donors of PMNs to agranulocytic patients, b/c the polys in myelofibrosis and CML are mature and normal, there’s just a lot of them 2/2 extramedullary hematopoeisis. The more you know.

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