Infection in immunocompromised hosts AIDS patients

Infection with T. gondii in these patients can involve the brain, the lung, and the eye. A multiorgan involvement with acute respiratory failure and haemodynamic abnormalities, as in septic shock, have been described (Lucet et al. 1993; Al-Kassab et al. 1995). The association of high fever, acute dyspnea, recent onset of thrombocytopenia, and a very high level of lactate dehydrogenase activity are suggestive of disseminated toxoplasmosis.

Toxoplasma encephalitis (TE) is the most common manifestation of infection in AIDS patients and is the most frequent cause of focal lesions in the central nervous system (Luft and Remington 1992). More than 95% of the cases are due to reactivation of a chronic infection and the incidence is thus proportional to the prevalence in the particular region. TE usually manifests itself when CD4 count falls below 100/

mm3.

In Europe and Africa 10-50% of HIV-infected patients sero-positive to Toxoplasma gondii will develop TE. Initial symptoms are often headache, confusion, and fever while focal symptoms will develop depending on the localization of the infected focus. Hemiparesis and/or abnormalities of speech are also major initial manifestations. Brainstem involvement causes neurological symptoms such as cranial nerve lesions, ataxia, palsies, and dysmetria. Non-focal symptoms can predominate and include weakness, disorientation, psychosis, confusion, or coma. Frequently multiple lesions occur. The onset can be insidious over weeks but can also be acute. Meningismus is rare. The cerebrospinal fluid may be normal or may have an increased number of cells and an increased protein level.

During the past decade the incidence of Toxoplasma pneumonia has increased in immunocompromised patients, probably due to improved diagnosis (Mariuz et al. 1997).

Toxoplasmic pneumonia has similar non-specific clinical manifestations as seen in pneumonia caused by Pneumocystis carinii. The onset tends, however, to be more rapid. Initial symptoms are usually dyspnea, fever, and a non-productive cough, which may rapidly progress to acute respiratory failure (Derouin et al. 1989). Chest roentgenographs commonly show bilateral intestinal infiltrates, with or without nodules, and hilar adenopathy. The mortality can be as high as 35% and extra-pulmonary disease is present in about 50% of patients with toxoplasmic pneumonitis (Beaman et al. 1995). Diagnosis is made by isolation or identification of the tachyzoite forms in broncho-alveolar lavage (BAL) fluid (Catterall et al. 1986). In a study conducted in France, 5% of BAL specimens were positive (Derouin et al. 1990).

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Severe infections of the entire gastrointestinal tract and pancreas have also been described (Luft 1989) as have cardiac tamponade or biventricular failure. Retinochoroiditis can be found. This manifestation caused by T. gondii is less haemorrhagic than retinochoroiditis caused by cytomegalovirus and is associated with a heavy vitriol haze and severe involvement of the vitreous and anterior uvea.

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