Plasmacytoma of the orbit is an uncommon pathology with fewer than 60 cases reported in the literature (1). Most often, a bony lesion infiltrates the extraconal space causing proptosis and diplopia. Extraocular muscle infiltration is usually associated with surrounding soft tissue involvement and is rarely an isolated finding (2). Localized treatment of orbital involvement previously has been limited to radiotherapy (3–5). We present a case of plasmacytoma limited to an extraocular muscle, which regressed after a localized injection of dexamethasone.
A 74-year-old man was evaluated for a 3-week history of a red right eye. He had a 14-month history of immunoglobulin G lambda multiple myeloma. At first relapse, he was treated with 3 cycles of bortezomib, cyclophosphamide, and dexamethasone. Because of treatment toxicity (proximal muscle weakness and peripheral neuropathy) and evidence of disease progression with widespread soft tissue plasmacytomata, his regimen was changed to a lenalidomide-based regime with reduced dose oral steroids.
On examination, visual acuity was 20/25, right eye and 20/40, left eye. Color vision was intact, and pupillary reactions were normal. The right eye had 3-mm axial proptosis with a palpable mass in the medial orbit and localized medial conjunctival injection but no associated lid swelling (Fig. 1A). There was limited abduction of the right eye (Fig. 1B), and the patient reported diplopia in right gaze. Intraocular pressures were 10 and 11 mm Hg in his right and left eyes, respectively. The right optic disc was swollen nasally, and the left fundus was normal as was automated perimetry in each eye.
Orbital computed tomography (CT) showed marked enlargement of the right medial rectus muscle causing mild proptosis and compression of the optic nerve in the orbital apex (Fig. 2). The remainder of the orbital soft tissue and bone structures was normal. The patient underwent right medial rectus biopsy with intramuscular injection of 2 mg dexamethasone. The biopsy showed extensive infiltration with plasma cells that were CD20−CD79+VS38c+ and lambda light chain restricted, consistent with plasmacytoma (Fig. 3). The patient responded well to the intramuscular dexamethasone and recent change in chemotherapy. Abnormalities on clinical examination completely resolved within 4 weeks (Fig. 4A, B), and radiotherapy was not required. A repeat CT scan showed that the medial rectus had returned to normal caliber (Fig. 4C). However, the patient's condition worsened, and he died 5 months after presentation to the eye department.
Plasmacytoma is a soft tissue mass composed of clonal plasma cells, which can arise anywhere in the body, and may infiltrate orbital or ocular structures. Plasmacytoma may be the presenting feature of myeloma or occur in established disease. Solitary plasmacytoma of bone (SBP) and, even more rarely, solitary extramedullary plasmacytoma (SEMP) may arise in the absence of other features of myeloma. In SEMP, progression to myeloma occurs in approximately 30% of patients with a median time to progression of 2–3 years (6). This is in contrast to patients with SBP where the progression rate is 70%. A new diagnosis of plasmacytoma warrants a full investigation for systemic disease. Plasma cell malignancy typically responds well to radiotherapy and steroid treatment (7).
Presenting signs in myeloma with orbital involvement include proptosis, reduced vision, diplopia, periorbital swelling, and ptosis. Uncommonly, patients may have ecchymosis, cellulitis, or necrobiotic xanthogranuloma. Most orbital lesions arise in the superotemporal quadrant (75%), with 90% occurring extraconally. Bone involvement with local infiltration is often present. Extraocular muscle involvement has a prevalence of 0.3% (2) and has not previously been described as an isolated finding. In all reported cases, extraocular muscle involvement has been associated with infiltration of tissues adjacent to the muscle including lacrimal gland, orbital bone, or contiguous eyelid (3–5).
Treatment options for plasmacytoma include localized radiotherapy, high-dose oral steroids, systemic chemotherapy, or a combination. Newer agents such as proteasome inhibitors (e.g., bortezomib) and immunomodulatory agents (e.g., thalidomide, lenalidomide) are now in routine use. Our patient was treated with chemotherapy and direct injection of dexamethasone into the extraocular muscle to prevent further optic nerve compression. Marked symptomatic improvement was noted within days of the injection, with complete regression of clinical signs and neuroimaging findings within weeks, despite a significant dose reduction in his oral steroid therapy. Orbital involvement in myeloma carries a poor prognosis with an average survival of 20 months, whereas median survival time for SEMP is 8.3 years (8). Previous reports indicate that patients often succumb to systemic disease before orbital involvement can be controlled, making the complete regression of signs and symptoms in this case particularly encouraging.
STATEMENT OF AUTHORSHIP
Category 1: a. Conception and design: S. L. Painter; b. Acquisition of data: S. L. Painter, J. S. Elston; c. Analysis and interpretation of data: S. L. Painter, E. Dickens, J. S. Elston. Category 2: a. Drafting the manuscript: S. L. Painter, J. S. Elston; b. Revising it for intellectual content: J. S. Elston. Category 3: a. Final approval of the completed manuscript: S. L. Painter, E. Dickens, J. S. Elston.
The authors acknowledge Dr Brendan McDonald and Dr Monika Hofer for the histological figures.
1. Burkat CN, Ban Buren JJ, Lucarelli MJ. Characteristics of orbital multiple myeloma: a case report and literature review. Surv Ophthalmol. 2009;54:697–704.
2. Surov A, Behrmaan C, Holzhausen HJ, Kosling S. Lymphomas and metastases of the extra-ocular musculature. Neuroradiology. 2011;52:909–916.
3. Thoumazet F, Donnio A, Ayeboua L, Breboin A, Diedhou A, Merle H. Orbital and muscle involvement in multiple myeloma. Can J Ophthalmol. 2006;41:733–736.
4. Adkins JW, Shields JA, Shields CL, Eagle RC, Flanagan JC, Campanella PC. Plasmacytoma of the eye and orbit. Int Ophthalmol. 1997;20:229–243.
5. Lazaridou MN, Micallef-Eynaud P, Hanna IT. Soft tissue plasmacytoma of the orbit as part of the spectrum of multiple myeloma. Orbit. 2007;26:315–318.
6. Dimopoulos M, Kiamouris C, Moulopoulos L. Solitary plasmacytoma of bone and extramedullary plasmacytoma. Hematol Oncol Clin North Am. 1999;13:1249–1257.
7. Mayr N, Wen B, Hussey D, Burns C, Staples J, Doornbos J, Vigliotti A. The role of radiation therapy in the treatment of solitary plasmacytomas. Radiother Oncol. 1990;17:293–303.
8. Sen S, Kashyap S, Betharia SM. Primary orbital plasmacytoma: a case report. Orbit. 2003;22:317–319.