# Gilteritinib in an Isolated CNS Recurrence of FLT3‐ITD Positive AML

## TL;DR

A patient with AML experienced a rare isolated CNS relapse and was successfully treated with a targeted FLT3 inhibitor.

## Contribution

This case highlights the possibility of isolated CNS relapse in AML and the effectiveness of FLT3-targeted therapy.

## Key findings

- An 82-year-old AML patient had an isolated CNS relapse without systemic disease recurrence.
- Targeted FLT3 tyrosine kinase inhibitor therapy led to complete remission and FLT3-ITD clearance from CSF.

## Abstract

Central nervous system (CNS) involvement in adult acute myeloid leukemia (AML) is uncommon and more frequently observed at relapse than at initial presentation. Typically, CNS relapse coincides with systemic disease, evidenced by detectable blasts in the bone marrow (BM) and/or peripheral blood. We describe a rare case of an 82‐year‐old patient with a history of AML, diagnosed three and a half years earlier, who developed an isolated CNS relapse while receiving palliative chemotherapy—without concurrent BM involvement or molecular evidence of systemic progression. Cerebrospinal fluid (CSF) analysis revealed blast cells harboring an FLT3 internal tandem duplication (FLT3‐ITD). Targeted therapy with an FLT3 tyrosine kinase inhibitor (TKI) achieved complete remission, with clearance of FLT3‐ITD from the CSF.

This case demonstrates that an isolated CNS relapse can occur in acute myeloid leukemia patients who are otherwise in complete hematological and molecular remission, and that targeted therapy, where applicable, as in our case against FLT3, can result in renewed remission.

Time course showing changes in cell count and FLT3‐ITD ratio in cerebrospinal fluid (CSF) from diagnosis through treatment.