Brain Pathology Case of the Month - April 2003



The immunohistochemical study was positive for Toxoplasma gondii demonstrating positive staining for the bradyzoites within the cysts and pseudo-cysts as well as individual tachyzoites in the necrotic tissue. Histopathological diagnosis of toxoplasmosis could be difficult due to the fact that cysts are difficult to recognize. These cysts may resemble those seen in other infections such as Leishmania donovani, Trypanosoma cruzi, Sarcocystis, Besnoitia and so on (1) Immunohistochemical stains now reveal the true nature of the microorganism, although electron microscopy can be used. Toxoplasmosis is a common CNS infection in AIDS patients (2,3). The characteristic lesion is a necrotizing acute abscess (1). Toxoplasmosis is well known as an intrauterine infection with devastating consequences but it is far more rare in settings outside of these. Although reported in post-transplanted patients, there have been virtually no reports of CNS toxoplasmosis in patients with diabetes mellitus. Only two cases related to patients suffering from diabetes mellitus have been recorded: One case in 1985 was reported in the Portuguese Literature (4) and another case in a Clinical Conference reported by the John Hopkins Hospital (5), the last in a renal-transplanted diabetic patient. Retinochoroiditis due to toxoplasma infection has been described in association with diabetes mellitus and Hepatitis C in HIV-negative patients (6). A case of cerebral toxoplasmosis associated to PML has been described in a patient with no immunodepression (7). Our patient presented a normal blood analysis and no risk factors for AIDS were recorded. Several studies demonstrated that neurons and other CNS cells are HIV-1 target cells (8) The PCR study in the present case did not demonstrate amplification of HIV-1 virus DNA "pol" region. It has been described that nested PCR is an extremely sensitive technique that can detect less than 10 viral copies in crude lysates (9). Zimmerman (10) showed that viral RNA can appear to be detected in only one out of 100,000 non infected cells. RNA viral copies in CNS samples were not demonstrated in this case. We can conclude that our patient has not been infected by HIV, as DNA HIV copies were not found.


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Contributed by F. Alameda, M. Natcher; MJ. Guardiola, MD, E. Galito, MD, I. Moysset, MD, S. Serrano, MD and F. F. Cruz Sanchez, MD

International Society of Neuropathology