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Sinus histiocytosis with massive lymphadenopathy (SHML) or Rosai Dorfman syndrome is a rare benign proliferative histiocytic disease of unknown origin. It predominantly affects the lymph nodes. The head and neck region usually in association with lymph node involvement, represents one of the most common extranodal areas affected by SHML. The other common extra nodal site is skin. Rarely, there is widespread dissemination with liver, kidney, respiratory organs, orbit, and eyeball involvement.1 The mean age of onset is 20 years (birth to 74 years).
A 57 year old woman with a 6 month history of double vision was referred to the Royal Victoria Eye and Ear Hospital, Dublin. She was found to have proptosis, ptosis, diplopia due to inferior rectus dysfunction, and restriction of elevation of the left eye. Her visual acuity was normal. Relevant investigations showed a high erythrocyte sedimentation rate (ESR) of 44 mm in the first hour, C reactive protein of 1.9 (normal less than 1). Her thyroid function tests, including thyroid microsomal and thyroglobulin antibodies, were normal. The antiacetyl choline receptor antibodies were also negative. A computed tomograph (CT) scan of the orbit was performed which showed an extraconal soft tissue mass with well defined margins in the inferomedial part of the left orbit and no separation from inferior and medial rectus. There was no bony erosion and the optic nerve appeared normal. She had an excision biopsy performed through lateral orbitotomy with Wright’s modification.
The tumour was removed within the capsule, it was found to be adherent to the inferior and lateral rectus. Histological examination of the tumour revealed an inflammatory process composed of aggregates of lymphocytes, with reactive lymphoid follicles, plasma cells, and groups of large histiocytes with abundant foamy cytoplasm. The inflammatory process extended around the nerves. There was no vasculitis, areas of coagulative necrosis, or granuloma formation. The large histiocytic cells were characterised by round to oval vesicular, hypochromatic nuclei with vesicular chromatin and abundant eosinophilic, foamy or clear cytoplasm with poorly defined cell borders. Emperipolesis was present. The phagocytosed cells were most often erythrocytes, lymphocytes, and polymorphonuclear leucocytes (Fig 1). Special stains for micro-organisms were negative. Immunohistochemical stains revealed the presence of diffuse S100 positivity within the cells. These cells also showed reactivity for the macrophage marker CD68. The diagnosis of Rosai Dorfman disease or SHML was confirmed.
Our patient did not have any lymphadenopathy or any other extranodal involvement. She did not receive any treatment and after 3 years’ follow up there was no sign of recurrence. She still had some residual hypotropia.
We report this case to draw attention to this unusual presentation of SHML confined to the orbit without any extranodal lesions, which to our knowledge is the only the third reported case of this nature. SHML is a rare, benign proliferative histiocytic disease with massive lymphadenopathy. Table 1 lists the causes of histiocytic proliferations in the orbit.
In one report of SHML, uveitis with papilloedema was the only presentation and in another report the only site of the lesion was lacrimal sac with the duct but these patients later developed cervical lymphadenopathy.2,3 Another case with ocular involvement was reported with uveitis and marginal corneal infiltrates in association with cervical lymphadenopathy.4 SHML is usually benign, low grade, and self limiting but death has been infrequently attributed to it. The condition has also been occasionally associated with the development of malignant lymphoma. Hodgkin’s and the follicular type of non-Hodgkin’s lymphoma and SHML have been identified in the same lymph node biopsy specimen.5,6 SHML may be associated with fever, leucocytosis, elevated erythrocyte sedimentation rate, and hypergammaglobulinaemia. Some studies suggest that human herpes virus (HHV-6) may play a part in pathogenesis of SHML.7 HHV-6 which infects many in childhood and remains latent in host cells can be reactivated by immunodeficiency. Serological evidence of HHV-6 and Epstein-Barr virus infection have also been documented in patients with SHML with their presence in affected tissues as well.7 SHML is usually self limiting but in some cases there was orbital involvement with compressive optic neuropathy, persistent uveitis with marginal corneal infiltrates, massive lymphadenopathy impairing cervical perfusion, and generalised lymphadenopathy with AA amyloidosis. These cases were treated with chemotherapy and oral steroids, the commonest being cyclophosphamide, vincristine, mercaptopurine, and prednisolone. Treatment causes regression of the tumour and resolution of cervical lymphadenopathy with minimal recurrence.8,9 Our patient did not receive any treatment and in the 3 year follow up there was no evidence of recurrence of the disease in the orbit or any sign of sinus histiocytosis elsewhere in the body.