a 17-year - old healthy male was seen with complaints of 
 painless swelling over the left eye for the past four weeks .
the 
 rest of the systemic and ocular history was not significant . 
 on examination
his vision was 20/20 both eyes . on slit - lamp 
 examination there was erythematous , subconjunctival nodular 
 mass in the left eye [ figure 1 ] .
the lesion had a smooth 
 surface with normal surrounding sclera and was not tender . 

hemoglobin , red blood cell count , total and 
 differential white blood cell count , platelet count , erythrocyte 
 sedimentation rate ( esr ) and blood smear were normal .
hematoxylin and eosin stained sections 
 showed a mixed cellular infiltrate , predominantly composed 
 of histiocytes mixed with lymphocytes , including plasma 
 cells and polymorphous nuclear leucocytes .
histiocytes were filled with pink cytoplasm and 
 contained lymphocytes , a pathognomic finding also known 
 as lymphophagocytosis [ figure 2 ] .
stains for bacteria , fungus 
 and acid - fast bacilli were negative . the patient was started on 
 systemic prednisolone ( 1mg / kg body weight ) on a tapering 
 dose for a period of four weeks . at six weeks
follow - up there 
 were no new lesions and the subconjunctival mass showed 
 no increase in size .
rosai and dorfman first described sinus histiocytosis with 
 massive lymphadenopathy in 1969.1 this disease mainly 
 presents as a massive painless cervical adenopathy in children 
 or young adults of african ancestry .
extranodal disease has 
 been found to occur in 43% cases which may be widespread 
 and most frequently involves the respiratory tract , paranasal 
 sinuses , visceral organs , skin , bone , central nervous system , 
 genitourinary tract , and orbit.2 other features include low- 
 grade fever , leukocytosis with neutrophilia , elevated esr , 
 and hypergammaglobulinemia.5 ocular involvement is 
 relatively uncommon ( 8.5% ) , and most cases have presented as 
 lymphoproliferation in the soft tissues of the orbit and eyelids.6 
 epibulbar mass as isolated finding of extranodal rdd is very 
 rare with only four cases reported in the literature so far.7 - 9 the underlying cause of rdd is unclear .
epstein - barr 
 virus2 and human herpes virus 6,10 have been isolated 
 in a few patients , but no clear association has been identified . 
 autoimmune disease , immunocompromise , and neoplastic 
 cell disease may be a cause , but this remains unclear.2 there 
 are rare associations with polycythemia vera , joint disease , 
 glomerulonephritis , hematological antibodies , and wiskott- 
 aldrich syndrome.2 the diagnosis of rdd is made on histopathology . 

characteristic histological features are histiocytic infiltration 
 admixed with lymphocytes and other inflammatory cells . 
 one typical feature of this entity has been emperipolesis , 
 with histiocytes demonstrating phagocytosed lymphocytes 
 and plasma cells .
the histiocytes are typically filled with pink 
 cytoplasm and often contain lymphocytes , a pathognomic 
 finding also known as lymphophagocytosis .
histiocytes in rdd , langerhan cell histiocytosis , and other 
 histiocytosis express s-100 , a neural tissue - specific protein ; 
 however , the pathophysiology of this s-100 expression remains 
 obscure .
although positive staining for s-100 strongly suggests 
 rdd , it is not absolutely required to make the diagnosis in the 
 presence of typical histology of rdd.9 the disease is classically 
 described to have an indolent , self - limiting course ; however , 
 this is not always the case .
the various stages of disease 
 progression are remission , recurrence , persistent but stable , 
 primary progressive and death caused by the disease .
the therapy for rdd is yet to be determined because of 
 the rarity of the disease and its propensity for spontaneous 
 remission .
excision , radiation therapy , chemotherapy and 
 systemic steroids have all been tried by different authors .
the 
 first line of interventional therapy to be considered is gross 
 total excision along with adjuvant steroids or more aggressive 
 chemotherapy or radiotherapy when necessary.11 in our patient 
 the disease was stable at six weeks , however a close follow- 
 up is needed to watch for any increase in size of the lesion or 
 systemic spread .
rosai - dorfman disease is an entity that is part of a group of 
 orbital / systemic disorders , including xanthogranulomas and 
 sclerosing inflammation of the orbit , which share numerous 
 anatomic , histological and pathophysiologic features .
the 
 differential diagnosis of rdd should include orbital sclerosing 
 inflammation , xanthogranulomatous disease , b - cell lymphoma , 
 and benign lymphoid hyperplasia.11 other disorders that 
 may superficially resemble rdd include burkitts lymphoma , 
 granulocytic sarcoma , rhabdomyosarcoma , neuroblastoma and 
 langerhans cell histiocytosis .
the growth pattern of lymphoma 
 and lymphoid hyperplasia are similar but these lesions do 
 not have the cicatrizing feature seen with rdd . sclerosing 
 inflammation and xanthogranulomas can be differentiated by 
 histological and immunohistochemical differences.11 although the orbit and eyelid are common extranodal sites 
 for ocular rdd , isolated epibulbar presentation is very rare . 

the authors would like to highlight that rdd may present 
 as epibulbar nodules without any other nodal or extranodal 
 involvement in young healthy adults and should be considered 
 in the differential diagnosis by clinicians when evaluating 
 epibulbar masses .
 rosai - dorfman disease is a rare idiopathic disorder characterized 
 by painless lymphadenopathy with cervical involvement in 
 more than 80% cases . 
 we report a case of rosai - dorfman disease 
 presenting as an isolated epibulbar mass in a healthy young adult 
 male . 
 epibulbar involvement in rosai - dorfman disease is a rare 
 presentation as can be seen from a review of all literature . 
 the 
 presentation , differential diagnosis and treatment are discussed . 
Case Report
Discussion