How Can Hyponatremia and Hemolysis Be Explained? Since blood osmolarity was low (259 mosmol/L) and urine osmolarity was high (508 mosmol/L), the syndrome of inappropriate antidiuretic hormone secretion (SIADH) was suspected. Three weeks after the first serologies, C. pneumonia and M. pneumoniae antibodies' rates did not rise, pointing out a cross-serological reactivity with T. gondii antibodies. Since the patient was in a critical condition and despite mild g6pd deficiency, gold standard anti-toxoplasmosis treatment 1 was promptly started after the serological diagnosis of recent T. gondii infection. Physicians should systematically consider acute toxoplasmosis as a possible diagnosis for any infectious syndrome with visceral (especially lung) involvement in patients who have recently travelled to or lived in the Amazonian area. Since lethal cases have been reported and since treatment associating pyrimethamine and sulfadiazine is efficient, such treatment should be promptly started immediately after serological results, without waiting for positive PCR or parasitic isolation.