A Case of Myeloproliferative Neoplasm‐Related Glomerulopathy Secondary to Primary Myelofibrosis With Acute Leukaemic Transformation

Glomerular diseases associated with myeloproliferative neoplasms (MPN) are rare, and most often present with proteinuria and kidney impairment. Its natural history is not well described, although it has been associated with poor prognosis in described cases. Here, we present a case of MPN-related focal segmental glomerulosclerosis (FSGS) secondary to primary myelofibrosis (PMF) and describe its progression with transformation of PMF to leukaemia. A 52-year-old gentleman was referred for lower limb swelling on a background of primary myelofibrosis requiring splenectomy 3 months prior. Kidney function was normal, but there was nephrotic-range proteinuria of 3.6 g (normal range, NR < 0.15 g) and mild hypoalbuminaemia of 29 g/L (NR 33-48 g/L). Urine microscopy was bland with no haematuria or pyuria. A kidney biopsy confirmed secondary FSGS with dysmorphic megakaryocytes in the glomerular capillaries, as well as immunohistochemistry demonstrating the presence of megakaryocytes and erythroid precursors in the interstitium, indicating the presence of extramedullary haematopoiesis. No deposits were seen on immunofluorescence or electron microscopy. Despite an initial response to high-dose corticosteroids, a relapse in proteinuria to 10.9 g was seen 5 months after diagnosis. This coincided with leukaemic transformation, which was confirmed on bone marrow biopsy. We describe a case of FSGS secondary to PMF presenting with normal kidney function and nephrotic syndrome. As far as the authors are aware, this is the first case to detail the progression of kidney disease before and after leukaemic transformation. Ongoing follow-up may provide useful insights into the natural history of this infrequent association.