Acute Monoblastic Leukemia (AML-M5) Presenting As Tonsillar Hypertrophy: An Unusual ENT Presentation.

Acute monoblastic leukemia (AML-M5) is a rare subtype of acute leukemia in children and may present with extramedullary involvement. We report the case of a nine-year-old boy with trisomy 21 who was referred to the otorhinolaryngology department for severe obstructive sleep apnea syndrome (OSAS). Clinical examination revealed marked bilateral tonsillar hypertrophy without associated signs of infection. Preoperative laboratory investigations performed prior to planned adenotonsillectomy demonstrated bicytopenia and circulating blasts on the peripheral blood smear. Bone marrow aspiration confirmed the diagnosis of AML, subtype M5. The patient was managed in the pediatric hematology and oncology department at Harouchi University Hospital in Casablanca. Following initiation of chemotherapy, a spontaneous regression of the tonsillar hypertrophy was observed, confirming its leukemic origin. This case highlights the importance of considering an underlying hematologic malignancy in cases of atypical tonsillar hypertrophy, particularly in children with known risk factors.