Monitoring of minimal residual disease in acute myeloid leukemia with frequent and rare patient-specific NPM1 mutations.

Nucleophosmin (NPM1) mutations in exon 12 are the most common genetic alternation in cytogenetically normal AML (CN-AML). Although mutation types A, B, and D represent the majority of cases, rare mutation variants of the NPM1 gene in individual patients do occur. In this study, we have evaluated a novel, DNA-based real-time quantitative polymerase chain reaction (RQ-PCR) for the detection of three of the most commonly occurring mutations and for six rare patient-specific mutation types, which represent 28% of all of the NPM1 mutations in our group of 25 CN-AML patients. Furthermore, the prognostic relevance of NPM1-based monitoring of minimal residual disease (MRD) in peripheral blood (PB), bone marrow (BM), and in specific cell subsets (CD34(+), CD34(-), CD34(dim)) of BM were evaluated. In 80% of the evaluable patients, a molecular relapse preceded a hematological relapse. Moreover, in this subset of patients, the molecular relapse occurred at a median of 97 days before the hematological relapse. Our compartment analysis showed a strong correlation between BM and PB (r = 0.907, P < 0.001) as well as a high copy number of mutated NPM1 in CD34(+) BM cells. In conclusion, we have demonstrated applicability of our presented RQ-PCR method for a large percentage of mutated NPM1 patients with CN-AML as well as the usefulness for long-term follow-up monitoring of MRD and the prediction of hematological relapse.

[Toxoplasmosis of the central nervous systems after allogeneic stem cell transplantation]. / Toxoplazmóza centrálního nervového systému po alogenní transplantaci krvetvorných bunek.

Toxoplasmosis is a rare opportunistic protozoal infection, which may occur in patients after hematopoietic stem cell transplantation. This disease originates almost exclusively from reactivation of latent infection in seropositive recipients. We present a case report of one patient with diagnosis of acute myeloid leukemia undergoing two allogeneic stem cell transplantations at two years interval. The second transplantation was complicated by the development of the toxoplasmic encephalitis in early posttransplant course. The initial neurological symptoms included diplopia caused by the paresis of right side motor branches of the 3rd and 6th cranial nerves due to a compressive lesion in basal ganglia. Patient suddenly deteriorated after an epileptic seizure followed by a loss of consciousness, bilateral ptosis and right side mydriasis. Prolonged sopor and bilateral mydriasis appeared because of the further lesion progression in basal ganglia and compression of the 3rd cranial nerve. After targeted therapy of Toxoplasma gondii the patient's clinical status improved and she regained consciousness. Unfortunately, examination of bone marrow later revealed the relapse of leukemia. We compared risk factors of the latent reactivation of infection in immunocompromised patients with published data. It is of interest that the toxoplasmosis of the brain developed in this patient after the second transplantation.

Detection and treatment of molecular relapse in acute myeloid leukemia with RUNX1 (AML1), CBFB, or MLL gene translocations: frequent quantitative monitoring of molecular markers in different compartments and correlation with WT1 gene expression.

OBJECTIVE: Our objective was to determine the value of frequent minimal residual disease (MRD) monitoring in acute myeloid leukemia (AML) as a robust marker of impending relapse, and whether treatment benefits patients during the MRD-positive phase of their disease. MATERIALS AND METHODS: Frequent MRD monitoring was performed in all AML treatment phases using real-time quantitative polymerase chain reaction for fusion transcripts (CBFB/MYH11; RUNX1/RUNX1T1 fusion transcripts of MLL gene) and for the Wilms' tumor (WT1) gene. A total of 2,664 samples, taken from 79 AML patients and 6 healthy volunteers, were examined. Presence of fusion gene was detected in 25 of 79 examined patients. RESULTS: Vast correlation was discovered for fusion transcripts as well as for the WT1 gene between levels in bone marrow (BM), peripheral blood, CD34(+) BM cells, and CD34(-) BM cells. WT1 expression, however, was usually positive for cases showing fusion transcripts negativity and in healthy volunteers. Moreover, no universal value of the WT1 expression could unequivocally discriminate between remission and relapse. Therefore, detection of molecular relapses relied on fusion transcripts only and was characterized by strong expression in CD34(+) cells. Considering relapsed patients, duration from molecular to hematological relapse was 8 to 79 days (median: 25.5 days). Twelve patients were treated (chemotherapy, gemtuzumab ozogamicin, or immunomodulation after allogeneic transplantation) for 21 molecular relapses and 14 responses to treatment were observed. CONCLUSIONS: Frequent quantitative monitoring of fusion transcripts is useful for reliably predicting hematological relapse in AML patients. Treatment for molecular relapse of AML can be successful.