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Editor,—Infectious mononucleosis (IM), a common disease in childhood, is an acute lymphoproliferative disease caused by Epstein–Barr virus (EBV),1 a member of the herpes virus family. The association of EBV infection with benign and malignant lymphoproliferative diseases, as well as its role in the pathogenesis of nasopharyngeal carcinoma, is well known.2 3 The course of IM is usually self limiting but can be extremely variable, ranging from asymptomatic to a fatal outcome. Fever, pharyngitis, lymphadenopathy, and hepatosplenomegaly are typical systemic manifestations. Essential for the diagnosis is an increase in relative and absolute numbers of lymphocytes and monocytes, including 20–40% atypical forms. Ocular involvement of IM is unusual and occurs often as a mild unilateral follicular conjunctivitis simultaneously with these other symptoms.4 We describe a girl with a conjunctival tumour as the first manifestation of IM; systemic symptoms of the disease occurred some days later.
A previously healthy 12 year old girl with a 10 day history of a painless red left eye was treated with antibiotic eye drops. Despite these, a unilateral conjunctival swelling developed, and the girl was admitted for further ophthalmological consultation. On examination, a 5 × 5 mm red coloured mass in the upper nasal conjunctiva of the left eye was observed. The globe was not displaced, the ocular motility and visual acuity were normal, and funduscopy was unremarkable. At this time, there were no palpable cervical lymph nodes. An excisional biopsy of the conjunctival tumour was performed. The initial histological diagnosis was “high grade malignant B cell lymphoma” and, consequently, the patient was referred to the department of oncology. On examination some days later, the girl was in a good general condition. Conjunctival vessel injection of the left eye and a mobile tumour of the upper nasal conjunctiva were observed (Fig 1). A 2 cm large left preauricular lymph node was visible, and some enlarged, tender, and mobile submandibular lymph nodes were palpable. A pharyngitis and moderate splenomegaly were also apparent. The remaining physical examination was unremarkable. Abdominal ultrasonography showed mildly enlarged para-aortal lymph nodes. The peripheral blood count revealed a relative and absolute lymphocytosis (WBC 13 ×109/l, 76% lymphocytes) with 33% atypical lymphocytes. Elevated levels of lactate dehydrogenase (658 U/l), aspartate aminotransferase (79 U/l), alanine aminotransferase (151 U/l), and bilirubin (1.1 mg/dl) were also detected. Serological tests confirmed the clinical diagnosis of an acute EBV infection.
Re-evaluation of the pathological findings by a lymphoma referral centre was undertaken. An extensive lymphocytic infiltrate and large necrotic areas were seen below an ulcerated conjunctival epithelium. The infiltrate mainly consisted of large polyclonal B immunoblasts, smaller mixed lymphocytes and polytypical plasma cells. Occasional immunoblasts, particularly those close to necrotic areas, expressed the latent membrane protein of the EBV (Cs1–4) (Fig 2) and were also positive for the EBV related proteins PE2 and BZ1. In addition, in situ hybridisation for EBV encoded early nuclear RNA (EBER) showed positive reaction in some immunoblasts. The growth fraction of the infiltrating cells was 60–80%, using the antibody Ki-67. On the basis of the conventional histology and immunohistology, in particular the polytypic nature of the immunoblasts and plasma cells as well as the demonstration of EBV infection, a diagnosis of IM involvement of the conjunctiva could be made; a malignant lymphoma was excluded. During the subsequent several weeks, all symptoms and signs of the IM resolved spontaneously.
Manifestations of IM in ocular tissues are rare, with the conjunctiva being the commonest tissue involved and then usually in the form of a follicular conjunctivitis.4 In general, the conjunctivitis occurs in parallel with the systemic symptoms of IM described above. Conjunctival involvement in the form of a swelling or a tumour has been reported previously.5-7 These occurred in 11, 38, and 14 year old patients, respectively, with the latter case being similar to ours in that the conjunctival tumour was the initial manifestation of the disease.7 As with our patient, all patients recovered within a few to several weeks. The main differential diagnosis of a unilateral salmon coloured conjunctival swelling without obvious systemic symptoms of an EBV infection is a malignant lymphoma; however, these infections are very rare in ocular tissues in children.8 The conventional histological picture with a dense lymphocytic infiltration consisting predominantly of lymphoblasts with areas of necrosis can appear similar to a high grade lymphoma. These diagnostic difficulties can be further exacerbated with the coexistence of, or subsequent development of, a malignant lymphoma following infectious mononucleosis.9 10 In the present case, the initial histological diagnosis made was malignant lymphoma. This diagnosis could be subsequently refuted on the basis of the immunohistochemistry and in situ hybridisation which demonstrated a polyclonal lymphocytic infiltrate and the detection of EBV associated antigens on the surface and within the nucleus of the infiltrating cells. The subsequent clinical progression with a self limiting course and the positive serology for EBV support the diagnosis of a lymphoproliferative process associated with an acute EBV infection and infectious mononucleosis. In conclusion, infectious mononucleosis should be considered in the differential diagnosis in patients with conjunctival lymphoid tumours.