IgG4-related disease

(IgG4-RD) is a multi-organ disorder characterized by infiltration of IgG4-positive plasma cells in the involved organ associated with a high level of serum IgG4. The disorder was first reported in 2001 in patients with autoimmune pancreatitis[1] and subsequently confirmed in other organs such as the salivary glands, hepatobiliary tract, lymph nodes, lungs, retroperitoneum and the kidneys.[2] IgG4-related kidney disease (IgG4-RKD) was first reported in 2004 as a tubulointerstitial nephritis associated with autoimmune pancreatitis.[3, 4] Although IgG4-RKD is now a well-established disease and some diagnostic check details criteria for the condition have been proposed,[5, 6] in some cases a definitive diagnosis is difficult. On the other hand, a case of IgG4-RKD after kidney transplantation

has never been reported. Here, we describe a case of suspected IgG4-RKD of the graft after living donor renal transplantation which was difficult to differentiate from a lymphoproliferative disorder. The transplant recipient developed acute glomerulonephritis after a streptococcal infection at 12 years of age, followed by a gradual deterioration in kidney function. She also had a history of bronchial asthma. In December 2009 at the age of 51 years she received a pre-emptive renal transplant from her 53-year-old husband. Because it was a blood type-incompatible transplant, she received rituximab, basiliximab, and three series of plasma exchange Epigenetics inhibitor as induction therapy, followed by administration of tacrolimus, mycophenolate Palbociclib mofetil, and methylprednisolone as maintenance immunosupression therapy. Ten months after the transplant she developed atypical mycobacteriosis, and was administered clarithromycin, ethambutol and rifabutin. There were no abnormal findings on protocol renal biopsies carried out 6 months and 1 year after transplantation. However, a protocol renal biopsy carried out 2 years after transplantation in February 2012, revealed plasma cell infiltration in the renal interstitium. Light

microscopy showed that the mononuclear cell cluster contained >50% of normal plasma cells, with no findings suggestive of rejection or BK virus nephropathy. There was also no ‘storiform’ fibrosis surrounding the infiltrating cells (Fig. 1A,B). Immunohistochemical staining showed a large number of IgG4-positive plasma cells, but a very small number of IgG1, IgG2 or IgG3-positive cells amongst the infiltrating cells. The percentage of IgG4-positive cells relative to IgG-positive cells was 80% (Fig. 1C). The majority of the plasma cells expressed kappa-type light chains. There were no SV40 positive cells in the specimen. In situ hybridization for detection of Epstein-Barr virus was also negative. Two years after transplantation the patient had a stable serum creatinine level of 1.26 mg/dL. Urinalysis and urine protein excretion were both normal. The serum IgG1 (1100.