Introduction:
Acute lymphoblastic leukemia (ALL) is the most common haematological malignancy in children. While chemotherapy remains the standard treatment, its toxicity can limit use. In such cases, biological therapies offer an effective alternative. We present a case of a 5-year-old with pre-B ALL who achieved remission and underwent haploidentical transplantation thanks to biological therapy, highlighting its role in pediatric leukemia treatment.

Aim:
The aim of the study is to present a case of a pediatric patient with ALL pre-B, where biological therapy was necessary due to high chemotherapy toxicity. We describe the treatment course, its effectiveness, and the importance of modern therapies when standard approaches are insufficient or carry a high risk of complications.

Case study:
We describe a 5-year-old girl diagnosed with pre-B acute lymphoblastic leukemia (ALL) after presenting with persistent non-specific symptoms. Chemotherapy according to the ALLIC 2009 protocol was initiated but led to severe complications, including acute pancreatitis and marked hypertriglyceridemia, requiring discontinuation of treatment and urgent plasmapheresis. A year later, following relapse, biological therapy with blinatumomab was introduced, leading to remission and enabling haploidentical transplantation.

Results and discussion:
Due to the high toxicity of chemotherapy, an alternative therapy was used. Blinatumomab proved effective, leading to remission and enabling transplantation. This case highlights the role of biologic therapy in treating children with ALL, especially when standard methods are too toxic or ineffective.

Conclusions:
Leukemias are severe childhood cancers. Chemotherapy is the conventional route, but biologic therapy, such as blinatumomab, provides an alternative for patients with high or ineffective treatment.