Tehran University of Medical Sciences Iranian Journal of Allergy, Asthma and Immunology 1735-1502 22 6 2023 12 28 600 603 Eduardo Liquidano-Perez Immunology Service, National Institute of Pediatrics, Secretariat of Health Mexico, Mexico City, Mexico Mariana Carmona Berrón Immunology Service, National Institute of Pediatrics, Secretariat of Health Mexico, Mexico City, Mexico Rosa Itzel Carrillo Nieto Immunology Service, National Institute of Pediatrics, Secretariat of Health Mexico, Mexico City, Mexico Celso Corcuera Delgado Pathology Department, National Institute of Pediatrics, Secretariat of Health Mexico, Mexico City, Mexico Lizbeth Blancas Galicia Immunodeficiencies Unit, National Institute of Pediatrics, Secretariat of Health Mexico, Mexico City, Mexico Selma Scheffler Mendoza Immunology Service, National Institute of Pediatrics, Secretariat of Health Mexico, Mexico City, Mexico 2022 03 08 2023 07 26 Chronic granulomatous disease (CGD) presents with granuloma formation and lethal infections. It is inherited in an autosomal or X-linked recessive pattern. We describe a 10-month-old patient with a fatal secondary HLH as a CGD primary manifestation. We carried out an autopsy and found noncaseating granulomas, an aspergilloma in the lung, and hemophagocytosis. We performed a DHR assay on the patient’s mother and grandmother, showing a bimodal pattern conclusive of X-linked CGD. Thus, our definitive diagnosis was CGD complicated by macrophage activation syndrome. CGD is caused by phagocytes’ inability to control pathogens, resulting in granulomas. Secondary HLH is a severe complication and could be characterized by the proliferation of macrophages and T lymphocytes and the production of proinflammatory cytokines. The early suspicion of this presentation helps establish a specific treatment, and the study of the carriers helps determine the etiology. https://ijaai.tums.ac.ir/index.php/ijaai/article/view/3480 https://ijaai.tums.ac.ir/index.php/ijaai/article/download/3480/2018