Orbital & Sinonasal Granulomatosis with Polyangiitis

An 86-year-old lady with history of ulcerative keratitis presented with one-month history of left lower eyelid swelling

There is a trans-spatial tumour-like mass in the left lower eye lid infiltrating the lacrimal sac and upper nasolacrimal duct with post-septal extension and early invasion of the intraconal fat and medial and inferior recti. It abuts and displaces the left globe. A second smaller nodule is present at the lateral aspect of the left orbit inseparable from the lacrimal gland. Both lesions show predominantly intermediate/low T2 signal intensity, moderate contrast enhancement, and an ADC of ~1.2 x 10^-3mm²/s on DWI (Fig 1 & 2).

Mucosal thickening in the left side nasal cavity floor extends along the nasal septum where there is mucosal ulceration / septal erosion with hypo-enhancement (Fig 2c). The hard palate and paranasal sinuses appear normal. 

Background

Granulomatosis with Polyangiitis (GPA) is an autoimmune anti-neutrophil cytoplasmic antibody (ANCA)- associated inflammatory disorder involving multiple body systems with orbital involvement occurring in 45-50% of patients [1,2].

Clinical Perspective

Imaging narrows the differential diagnosis guiding further clinical investigations and requirement/site for biopsy. The patient, in this case, had a known history of GPA and was ANCA-c positive with raised serine antiproteinase 3 (PR3). Biopsy from the lower eyelid demonstrated dense mixed inflammatory infiltrate with granulomatosis inflammation and tissue necrosis. Imaging is also important to assess the known complications of GPA such as optic nerve compression, extension into the cavernous sinus and late-stage enophthalmos with fibrosis (low T1 & T2 signal) [3].

Imaging Perspective

Tumour-like masses in GPA are typically contrast-enhancing with relatively low T2 signal, unilateral, extra-conal and may be trans-spatial [4] as shown in this case. The DWI of GPA was helpful as it showed relatively less restriction of diffusion (high ADC of ~1.2 x 10^-3 mm2/s), than is typically found in malignancy [5].  Of course, ADC values may vary between institutions as a function of scanner type and magnetic field strength [6] and there is no blanket threshold to distinguish benign from malignant disease. However, the main differential diagnosis of GPA at this site is lymphoma, a malignancy which typically shows marked restriction of diffusion resulting in ADC level often less than 0.6 x 10^-3 mm2/s [7], much lower than those of GPA. One other helpful clue to the diagnosis of GPA is the presence of sinonasal disease. In this patient granulomatous inflammation was found in the left side of the nasal cavity on visual inspection. Sinonasal disease is common in GPA (59%) and can spread to the orbit [8]. Granulomatous involvement and avascular necrosis from inflammatory cell infiltrates may cause erosion/destruction of the nasal septum, which may spread to the nasal bridge, nasal turbinates and maxillary antra [9].  The distinction of GPA from other inflammatory-type conditions such as such as IgG4 related disease and idiopathic orbital inflammation is more problematic and beyond the scope of this discussion. [10,11]

Outcome

The inflamed nasal cavity mucosa was not biopsied as ENT assessment was undertaken after biopsy of the orbital lesion. This patient’s orbital and nasal disease responded to steroid treatment without the need for escalation to monoclonal antibody therapy. Surgery is rarely indicated with GPA and mainstay of management is medical therapy.

Take-Home Message/ Teaching Points

1. DWI in this case, was valuable to suggest GPA was more likely than lymphoma

2. The sinonasal region should be reviewed in the context of orbital disease.