Toxoplasma gondii infection diagnosed by tNGS in a patient with acute lymphoblastic leukemia: a case report.

backgroundToxoplasma gondii (T. gondii) is an obligate intracellular protozoan parasite. In the context of hematological malignancies, the immunosuppression induced by chemotherapy and the underlying disease state render patients highly vulnerable to T. gondii reactivation. The consequences of such infections can be extremely severe, often leading to life-threatening complications such as toxoplasmic encephalitis (TE). There are few reports on the detection of T. gondii infection in cerebrospinal fluid (CSF) by targeted next-generation sequencing (tNGS). CASE PRESENTATION: A 5-year-old girl diagnosed with ALL developed an unexplained fever and cough during the course of chemotherapy. Initial routine laboratory tests failed to identify the causative pathogen. Due to the persistence of symptoms and the patient’s immunocompromised state, further investigations were pursued. tNGS of blood and CSF unexpectedly revealed T. gondii sequences. Brain MRI demonstrated abnormal signals, including ring-line high signal, which are characteristic of TE. Based on these findings, a definitive diagnosis of TE was established. The patient was promptly initiated on a combination therapy of trimethoprim-sulfamethoxazole (SMZ-TMP) and clindamycin, and the patient responded well to the treatment and subsequently discharged in stable condition and continued on maintenance therapy to prevent relapse.

conclusionsThis case highlights the timely use of tNGS, a new tool with fast speed, high accuracy, and cost-effectiveness that can help identify atypical infections and start early therapy. Moreover, tNGS has great potential in various other clinical scenarios. In critically ill patients with complex infections where time is of the essence, tNGS can provide a comprehensive pathogen profile in a short time.