Granulomatosis with polyangiitis presenting as obstructive uropathy and vasculitic myopathy.

Abstract

A 63-year-old male presented with 3 months of urinary retention, progressive bilateral lower limb muscle weakness, 18-kg weight loss and eye redness. Prior to admission, MRI revealed marked enlargement of the prostate (Fig. 1A) and prostatic biopsy found granulomatous inflammation (Fig. 1B). During admission, testing revealed a positive pANCA (perinuclear antineutrophil cytoplasmic antibody) and MPO (myeloperoxidase antibodies; >8.0 units, ref. <0.4). CRP was elevated (179.2 mg/l; ref. <8.0) but creatine kinase was normal (12 U/l; ref. 39–308). Extensive infectious workup, including metagenomic sequencing, was negative. MRI of the proximal lower extremities demonstrated diffuse T2 hyperintensity in muscles (Fig. 1C). Biceps femoris muscle biopsy showed a necrotizing vasculitic myopathy (Fig. 1D). Prednisone and rituximab were initiated for induction therapy of granulomatosis with polyangiitis (GPA), resulting in rapid improvement of muscle weakness, episcleritis and constitutional symptoms. GPA is a form of ANCA-associated vasculitis that predominately affects small vessels. The most common sites affected include the ears, nose, throat, lungs and kidneys. Urologic manifestations are rare, affecting <1% of cases [1]. Granulomatous prostatitis in GPA usually presents with obstructive symptoms and more rarely with acute urinary retention [1]. Vasculitic myopathy is similarly uncommon and typically presents with a combination of myalgias and muscle weakness but may have a normal creatine kinase [2].