Morphology of the HIV versus the diabetic cotton wool spot

Background: Retinal cotton wool spots (CWS) have long been associated with many systemic diseases, including diabetes mellitus and infection with the human immunodeficiency virus (HIV). The pathogenesis of the diabetic CWS ha s been well established but is not clear in HIV disease. This study documen ts a morphological difference between cotton wool spots observed in diabete s mellitus and HIV infection. Methods: Electronic images of 47 diabetic CWS and 38 HIV CWS were compared in terms of eccentricity. Each CWS was enlarg ed, and its major and minor axes were determined. Eccentricity was determin ed by use of a simple ratio of major vs. minor axis. The eccentricity of th ese diabetic and HIV CWS were compared by use of the Mann- Whitney rank sum test to check for significance. Results: The HIV CWS was significantly mor e eccentric (p less than or equal to 0.001), thus suggesting a different mo rphology than its diabetic counterpart. Conclusions: There seems to be a si gnificant difference in the morphology of the cotton wool spots observed in diabetes mellitus compared with those observed in HIV infection. This diff erence suggests that, at some level, the pathogeneses of these two CWS are not the same. Clinically, the practitioner should strongly suspect HIV dise ase in a patient with boomerang-shaped cotton wool spots.