Clinical manifestations
Toxoplasmosis can be categorized, depending on the immune status of the patient, into 4 groups (1, 2).
  1. Immunocompetent patients (children, adults, pregnant women) are predominantly asymptomatic. However, 10%-20% of those patients may develop cervical or occipital lymphadenopathy or a flu-like illness. Generally, symptoms are self-limited and resolve within weeks to months. Recent data have suggested an association between Toxoplasma gondii infection and various psychiatric or neurologic syndromes such as schizophrenia, Alzheimer syndrome, and even suicide (7, 8).        
  2. Immunodeficient patients. The reactivation of chronic situations may lead to life-threatening disease (1, 2). In these individuals, the Central Nervous System (CNS) is affected the most, and includes encephalitis, decrease of mental status, seizures, movement disorders and other psychiatric findings. Toxoplasmosis in immunodeficient patients can present as chorioretinitis, pneumonitis or involve multiple organs, finally leading to acute respiratory failure, myocarditis and hemodynamic abnormalities (1).
  3. Ocular toxoplasmosis constitutes an important cause of chorioretinitis and may be the result of acquired or congenital infection (1, 2). Patients who have been infected by vertical transmission can be asymptomatic until the second and the third decade of life, when lesions develop in the eyes (1). Chorioretinitis in those individuals is more often bilateral (2).
  4. In congenital toxoplasmosis, as has been said, the severity of clinical and ultrasonographic findings in congenitally infected fetuses is inversely related to the gestational age at the time of primary maternal infection. As a result, a first trimester maternal infection usually leads to more severe manifestations (4, 5, 10). Prenatal ultrasonographic findings include intracranial calcifications, ventricular dilatation, hepatic enlargement, ascites, and increased placental thickness (9). In some cases, spontaneous abortion, prematurity, or stillbirth may occur (1, 2). In general, congenital toxoplasmosis is characterized by a wide spectrum of clinical manifestations, but in 70-90% of infected newborns it is subclinical, although involvement of CNS is a hallmark (1). Chorioretinitis, hydrocephalus and intracranial calcifications constitute the so-called classic triad of congenital toxoplasmosis (1). Other clinical manifestations include microcephaly, strabismus, blindness, epilepsy, mental retardation, petechiae due to thrombocytopenia, anemia, hepatosplenomegaly, jaundice, myocarditis, pneumonitis and respiratory distress (9).