LATE RELAPSE OF ANCA ASSOCIATED VASCULITIS PRESENTING AS OBSTRUCTIVE NEPHROPATHY DUE TO RETROPERITONEAL FIBROSIS

ANCA associated vasculitis (AAV) usually presents with constitutional symptoms, and involvement of upper and/or lower respiratory tract and kidneys.  While kidney involvement is more common in microscopic polyangiitis, pulmonary or ENT involvement is more common in granulomatous polyangiitis.  AAV presenting in the form of retroperitoneal fibrosis is rare.  Late relapse of AAV as retroperitoneal fibrosis is not reported.  We present a case of AAV who initially presented as rapidly progressive glomerulonephritis (RPGN), remained in remission for several years and then had a relapse of AAV presenting as retroperitoneal fibrosis (RPF) causing obstructive nephropathy

Case Report:

 A 48 year old male presented to the renal outpatient services with low backache for last four months, which was gradually increasing in intensity since last one month. He had shown in orthopedics. Evaluation did not reveal any neurological deficit and X-ray lumbosacral spine was normal.

He was a known case of ANCA vasculitis under regular follow-up since last nine years.  when he had initially presented with RPGN.  Kidney biopsy then had shown microscopic polyangiitis (PR-3 antibody positive).  He had been treated with steroids, cyclophosphamide and plasmapheresis.  He had achieved complete remission, and thereafter received maintenance immunosuppression with steroids and azathioprine for almost seven years.  Renal functions remained stable with serum creatinine 0.8 mg/dl (eGFR 111 ml/min/1.73 m2) and PR-3 antibodies were negative.  He was off immunosuppression for six months prior to current illness.

The patient was admitted under nephrology for evaluation.  On examination BP was 114/90, there was no edema, icterus or lymphadenopathy.  Urine routine and microscopy was normal with urinary protein-creatinine ratio 255 mg/g. The serum creatinine had increased to 1.15 mg/dl  (eGFR 79 ml/min/1.73 m2).  Ultrasound showed bilateral hydroureteronephrosis (HDUN) with normal sized kidneys.  MRI abdomen (Fig 1) revealed irregular shaped peri-aortic soft tissue along the infra-renal aorta at it its anterior and lateral aspects extending caudally to the level of the common iliac bifurcation.  It was T1 isointense and T2 hyperintense showing diffusion restriction and delayed enhancement.  There was no retroperitoneal lymphadenopathy.  Both ureters were also encased with medial displacement.  The features were suggestive of RPF. MR urogram (Fig 2) confirmed bilateral obstructive HDUN.  PET-CT revealed active FDG uptake in the RP mass.  The differential diagnoses considered were IgG4 related disease and lymphoma.    Serum IgG levels were normal. CT guided biopsy of the mass was done.  There was dense plasma cell infiltration with necrosis in which no malignant features were seen.  The biopsy was compatible with vasculitis. The serum PR-3 was strongly positive.  Bilateral double-J stenting of the ureters were done.  He was treated with pulse methylprednisolone 500 mg once daily for three days followed by oral steroids.  He was also administered Inj Rituximab 1g, repeated 6 monthly. 30 months later his renal functions are normal and PR-3 antibodies undetectable.

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Low backache is a common problem in the population.  In a known case of AAV it is important to have a high index of suspicion of retro-peritoneal fibrosis so that the diagnosis is not missed / delayed.