Chronic myeloid leukemia presenting with isolated central nervous system lymphoid blast crisis: A case report.

BACKGROUND

Chronic myeloid leukemia (CML) is a myeloproliferative neoplasm driven by the Philadelphia chromosome, typically progressing through chronic, accelerated, and blast phases. Blast crisis may be myeloid or lymphoid. Isolated central nervous system (CNS) involvement is rare and represents a diagnostic and therapeutic challenge.

CASE PRESENTATION: We report a 40-year-old man with no prior hematologic history who presented with four months of progressive lower-limb paresthesias, neuropathic pain, and subacute weakness impairing ambulation. Neurologic examination revealed asymmetric paraparesis, hyporeflexia, and distal hypoesthesia in a stocking distribution, consistent with a subacute asymmetric sensorimotor polyradiculoneuropathy. Complete blood count demonstrated marked leukocytosis with neutrophilia, left shift, and circulating blasts. Contrast-enhanced spinal magnetic resonance imaging showed extensive leptomeningeal enhancement. Cerebrospinal fluid (CSF) analysis revealed pleocytosis, hypoglycorrhachia, and elevated protein levels; flow cytometry identified 14% B-lymphoid blasts (CD34+, CD19+, CD20+, CD22+). Bone marrow aspirate and biopsy showed hypercellularity with trilineage hematopoiesis, basophilia, and small hypolobated megakaryocytes, without a significant increase in blasts (<5%). Cytogenetic analysis identified t (9; 22), and molecular testing confirmed the BCR::ABL1 p210 transcript, consistent with chronic-phase CML. An isolated CNS lymphoid blast crisis was diagnosed. Treatment with HyperCVAD (Block B only) plus dasatinib 140 mg daily resulted in neurologic improvement and hematologic normalization. After five cycles, CSF clearance was achieved, followed by consolidation with haploidentical allogeneic hematopoietic stem cell transplantation. The patient remains in complete remission.

CONCLUSIONS

Isolated CNS blast crisis may represent the initial manifestation of CML. Prompt recognition through integrated neurologic, hematologic, and molecular evaluation is critical to enable timely, targeted therapy.