Orbital Lymphoma Masquerading as Thyroid-Associated Orbitopathy

Abstract

A 70-yr-old woman 1 was referred because of orbital pain, bilateral proptosis, eyelid swelling, inflammatory symptoms, and visual impairment. Her symptoms had begun 2 yr earlier, and a computed tomography (CT) scan of the orbits at the time had shown mild proptosis and enlargement of the left superior rectus muscle. Thyroid function tests revealed mild hypothyroidism with negative thyroid autoantibodies. A diagnosis of thyroid-associated orbitopathy (TAO) was made. The patient had a history of mild chronic lymphocytic leukemia, without lymph node or solid organ involvement. She was treated with L-thyroxine and an 18-month course of low-dose methylprednisolone and azathioprine, with a partial improvement of her eye manifestations. Her eye symptoms recurred, however, when immunosuppressive treatment was withdrawn and consequently she was referred to our department. Physical examination (Fig. 1, upper panel) showed marked, bilateral proptosis, soft tissue inflammation, and mild impairment of ocular movement (1). There was no upper lid retraction. Thyroid function tests were normal on L-thyroxine with negative thyroid autoantibodies, including TSH receptor autoantibodies. A CT scan of the orbits (Fig. 1, upper panel) showed bilateral proptosis, mild enlargement of extraocular muscles, together with a diffuse nodular infiltration of soft tissues, involving the eyelids and the orbital cavity. These features suggested ocular involvement by a neoplastic process, rather than TAO, in which the typical finding is the enlargement of extraocular muscles (rectus inferior medial superior) (2). An orbital biopsy of affected tissue (Fig. 1, lower panel) revealed a dense infiltrate of small B lymphocytes staining positive for CD20, CD5, and bcl-2, therefore supporting the diagnosis of B cell chronic lymphocytic leukemia involving the orbits (3, 4). Treatment with clorambulacil was commenced. Four weeks later, improvement of eye manifestations was evident, and this was sustained at the next follow-up visit 4 months later (Fig. 1, middle panel). Orbital manifestations went into complete remission at the latest follow-up visit (10 months after clorambucil therapy was started). Orbital lymphoma can mimic TAO. In atypical cases of TAO, like those who have no history of Graves’ disease, no TSH receptor antibodies, and absence of upper lid retraction, alternative diagnoses should be considered (5). In these cases, orbital imaging should always be performed. Indeed, the unusual eye muscle involvement