A Case of Myeloma Kidney with Perinuclear Anti-Neutrophil Cytoplasmic Antibody and Anti-Myeloperoxidase Positivity: The Importance of Determining the True Cause of Renal Impairment

Acute kidney injury (AKI) is a common presentation which can result from a number of different underlying pathological processes. Haematological malignancies, particularly multiple myeloma (MM), are known to frequently present with AKI. Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a rare condition which can cause crescentic glomerulonephritis (GN), resulting in AKI. We present the case of a 60-year-old man who presented with clinical features suggestive of AAV in the context of blood tests which demonstrated AKI and positive perinuclear ANCA (p-ANCA) and anti-myeloperoxidase (anti-MPO) titres. Further investigations demonstrated an underlying diagnosis of MM. A renal biopsy was ultimately required to determine the cause of AKI, a cast nephropathy. This case is the first to our knowledge which demonstrates a rare situation in which myeloma kidney is associated with positive p-ANCA and anti-MPO titres, without any evidence of a crescentic GN. It highlights the importance of following up on all investigations sent in the context of AKI, even when a potential diagnosis seems evident. Furthermore, it demonstrates the role of renal biopsy in confirming a diagnosis in the context of AKI with multiple differential diagnoses.

The patient with myeloma

Renal impairment is a common feature of multiple myeloma and often the presenting symptom of a patient with symptomatic myeloma. ‘Myeloma kidney’ results from the excess of immunoglobulin light chains which form aggregates and casts that result in tubular obstruction; however, light chains may cause renal damage with a variety of mechanisms, which often may coexist in the same patient. The presence of significant renal dysfunction in a patient with myeloma is associated with a risk for significant complications, including early death. Myeloma kidney is usually associated with high tumour burden and high rates of paraprotein production.Patients with renal impairment should be managed immediately with appropriate antimyeloma therapy and supported vigorously. New drugs such as bortezomib are probably the most effective therapies for patients with renal dysfunction and may improve renal function in a significant proportion of patients with myeloma-related renal impairment, especially with dexamethasone at high doses. Other drugs such as thalidomide or lenalidomide may also be helpful in certain patients. Direct removal of the toxic free light chains may improve outcomes in some patients, but randomized studies are still ongoing. The role of plasmapheresis has not been established.Autologous stem cell transplantation, with appropriate dose adjustments for high-dose melphalan should be offered in eligible patients, even those on dialysis, although this procedure may be associated with a higher risk of toxicity in patients with more severe renal dysfunction. Renal transplantation may be an option for selected patients who have responded well to therapy.