Abstract
Myeloperoxidase (MPO) is found in the lysosomes of monocytes and neutrophils, serving as a crucial component in the elimination of infections through the process of phagocytosis via neutrophils. Consequently, individuals with MPO deficiency exhibit a significantly heightened susceptibility to serious infections and chronic inflammatory diseases. In a clinical case, a 37-year-old Iranian woman presented with a chronic history of bacterial and fungal infections dating back to her childhood. She has no family history of similar diseases and has used antibiotics and antifungal medications. A comprehensive clinical assessment revealed that she is well-nourished and without acute distress, neurological symptoms, or cutaneous manifestations. A complete blood count (CBC) with differential white blood cell (WBC) count showed a decreased number of neutrophils despite normal WBC counts, and peripheral blood smear (PBS) revealed reduced neutrophil granulation, abnormal neutrophil morphology, decreased chromatin condensation, and cytoplasmic hypogranulation. So, the patient was diagnosed with MPO deficiency, a rare condition requiring early diagnosis and management.