Granulomatosis with polyangiitis masquerading as giant cell arteritis

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A 65-year-old man presented with headache, weight loss, occasional scalp tenderness, and visual loss in his left eye, which worsened over a number of weeks to bare light perception. There was a left relative afferent papillary defect with a swollen disc and a small amount of associated hemorrhage. Erythrocyte sedimentation rate (ESR) was 16 mm/1st h, C-reactive protein (CRP) was 3.3 mg/l (normal \7). Temporal artery biopsy demonstrated no evidence of arteritis. On initiation of corticosteroids, his vision improved dramatically and the corticosteroids were subsequently weaned to zero over a period of 6–8 weeks. Three months later, he re-presented with left-sided ptosis and worsening headache. There had been weight loss (7 kg within the prior 6 months). Examination revealed a complete left-sided ptosis, with normal eye movements. Visual acuity was measured at 6/5 on the right and 6/9 on the left. Slit-lamp examination was unremarkable. Laboratory investigations revealed mild eosinophilia (0.78, range 0.04–0.4 9 10/l), an ESR of 9 mm/1st h, and a CRP of 13 mg/l. Serum complement levels were reduced: C3 \0.04 g/l (range 0.75–1.88), C4 \0.01 g/l (range 0.14–0.61). Dipstick urine testing was negative for blood and protein. Urinalysis was negative for casts and red cells. Serum anti-nuclear antibody, extractable nuclear antigen, anti-neutrophil cytoplasmic antibody (ANCA), PR3 and MPO antibodies were negative. Chest radiograph was normal. Dedicated gadolinium-enhanced magnetic resonance imaging (MRI) of the orbits and brain revealed dural enhancement and thickening over the left and right temporal lobes (Fig. 1), with normal orbits. Cerebrospinal fluid (CSF) examination demonstrated an absence of cells with normal glucose and protein concentrations. CSF bacterial and TB cultures and CSF ANCA were negative. The patient was commenced on high-dose corticosteroids (1 mg/kg/day), with resolution of his headache over the following days. The CRP level and eosinophilia normalized quickly. The ptosis improved significantly but not completely. Biopsy of the fronto-temporal dura mater demonstrated thickened dura (Fig. 2a), with multifocal infiltration by cellular aggregates comprised of an admixture of mature lymphocytes, plasma cells, and multinucleate giant cells (Fig. 2c). Foci of necrosis were present (Fig. 2b), and characterized by accumulation of polymorphonuclear A. McCarthy T. Lynch K. O’Rourke (&) Dublin Neurological Institute at the Mater Misericordiae University Hospital, 57 Eccles St, Dublin 7, Ireland e-mail: killian.orourke@gmail.com