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Clinical Characteristics

There are several distinct patterns of clinical infection, but it is first important to note that the vast majority of those infected by T. gondii will not have any clinical symptoms.

Generalized, Acquired Infection

The clinical symptoms are very nonspecific, particularly in the chronic form of the infection. If the patient is not immunosuppressed, the incubation period is 10-14 days and the main complaints will be of moderate fever and lymphadenopathy (the most common symptoms), myalgia, and general ill health. Some patients may have a stiff neck, loss of appetite, nausea, vomiting, and abdominal pains. The liver and spleen may be enlarged. Other patients may have cardiac symptoms. There may be a rash and conjunctivitis. The illness usually lasts about 1 month, but in some patients may persist for 3-4 months.

When the patient is immunosuppressed, the symptoms are usually more acute and cardiac involvement is more common. There may be myocarditis and pericarditis. Myocarditis generally occurs with muscle fiber degeneration, edema, and an eosinophilic infiltrate. The degree of pericardial involvement is variable, with small to moderate-sized pericardial effusions that rarely lead to tamponade. Patients typically present with fever and sudden heart failure: myocardial biopsy may be diagnostic. Endocarditis has not been described in toxoplasmosis.

At autopsy, T. gondii is found incidentally in the majority of lungs of immunosuppressed patients, but clinical pulmonary disease is a rare complication of toxoplasmosis. Patients present with features suggestive of an atypical pneumonia. They are likely to be dyspneic and febrile with minimal cough and no sputum production.

When the patient is immunosuppressed, polymyositis is rare but has been described: skin involvement may occur, with muscle invasion producing dermatomyositis. Toxoplasmosis can produce a number of cutaneous manifestations that include a maculopapular rash, urticaria, pruritus, erythema multiforme, and ulcers.

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