CD19-Negative Acute Lymphoblastic Leukemia (ALL): A Case Report and Review of Literature on a Rare Phenomenon De Novo and a Future Induced Struggle in Relapse.

Acute lymphoblastic leukemia (ALL) is the most common childhood malignancy, with most cases arising from B-cell precursors expressing the CD19 marker. CD19 negativity in B-lineage ALL (B-ALL) is very rare de novo and poses diagnostic and therapeutic challenges. Sometimes, de novo CD19-negative B-ALL is associated with hypercalcemia, which is a potentially life-threatening metabolic disorder in children, rarely occurring in cancers. Most often it is reported in solid tumors, and few cases are reported in pediatric acute leukemia. CD19-negative B-ALL relapse is also an increasing dramatic event, secondary to immunotherapy. We describe a ten-month-old infant presenting with hypercalcemia, anemia, and osteolytic bone lesions. Bone marrow analysis revealed CD10-positive and CD19-negative B-ALL. The patient achieved complete remission but later experienced two relapses and died of respiratory failure after a second allogeneic hematopoietic stem cell transplantation (HSCT). Only nine cases of de novo CD19-negative B-ALL have been reported so far. Many are associated with hypercalcemia and osteolytic lesions. However, here we highlight the clinical impact of the more common secondary form of CD19-negative B-ALL as a relapse of CD19-positive ALL, right after the administration of targeted immunotherapy.