retinal vein occlusion and paroxysmal nocturnal hemoglobinuria

Paroxysmal nocturnal hemoglobinuria (pnh) is a rare disorder associated with increased risk for thrombosis and reduced life expectancy. retinal vein occlusion (rvo) is a frequent cause of vision loss but its relationship with pnh has not been studied systematically. patients followed up for rvo in our ophthalmology department were screened for the presence of a pnh clone in peripheral blood by means of flow cytometry. the presence of other well-documented risk factors for rvo was also analyzed. in a series of 110 patients (54 males, median age of 67) we found no evidence of pnh. most patients (97/110) had cardiovascular risk factors and/or hyperhomocysteinemia (67/110). inherited thrombophilias were rare (three confirmed cases). therefore, pnh does not appear to play a role in the development of rvo. however, this finding does not necessarily apply to young patients and/or those with no conventional risk factors for rvo, due to the low number of patients in these subgroups in our population.