Thymic Involvement in Chronic Granulomatous Disease of Childhood

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1 Thymic Involvement in Chronic Granulomatous Disease of Childhood Joseph Junewick, MD FACR 07/16/2010 History 3 year old male with multifocal osteomyelitis. Diagnosis Thymic Involvement in Chronic Granulomatous Disease of Childhood Discussion Chronic granulomatous disease (CGD) is a disorder of neutrophil function, affecting one child per 200, ,000 live births in the United States. It is most commonly transmitted in an X-linked recessive manner. It is characterized by recurrent infections with catalase-positive organisms, such as Staphylococcus, Burkholderia cepacia, Nocardia, Mycobacteria, Serratia, Klebsiella, Pseudomonas species, and fungi, especially Aspergillus species and Candida. Recurrent bacterial and fungal infections result in lymphadenitis, abscesses, and granuloma formation, with most patients presenting within the first 2 years of life. CGD is caused by mutations in one of four genes encoding subunits of the phagocyte NADPH (nicotinamide adenine dinucleotide phosphate) oxidase. The phagocytosis process leads to activation of NADPH oxidase and free radical superoxide formation in the phagocytic vacuole. Oxygen radicals are the principal means by which microbial killing occurs in the phagosome. In CGD patients, a dysfunctional NADPH oxidase prevents oxygen free radical formation. Some microbes possess catalase which impairs oxygen free radical action. Although the neutrophils can phagocytose these catalase-positive microbes, the lack of oxygen radicals renders the neutrophils unable to kill them. These microorganisms can then survive within the phagosome. Therefore, chronic inflammatory cell reactions result in granuloma formation in a variety of organs. Most patients manifest symptoms within the 1st year of life. The disorder is much more common in males than females. The major sites of infection are those that come into contact with the external environment: the lungs, skin, and gastrointestinal tract and the lymph nodes that drain these organs. Hematogenous seeding can lead to osteomyelitis and liver abscesses. The thymus can be involved in CGD. Differential diagnosis of thymic disease includes Langerhans cell histiocytosis, thymic cysts and teratoma. The prognosis for patients with CGD has continued to improve since the disease was initially described. With a multifaceted therapeutic approach comprising prophylactic antibiotics, early treatment of infections with parenteral antibiotics, percutaneous drainage, surgical intervention, and the use of granulocyte infusions and interferon therapy, most patients are now expected to survive into adulthood. Mortality is often related to pneumonia or sepsis from Aspergillus or B cepacia. Findings CT-Rounded areas of low attenuation in the thymus with multiple peripheral pulmonary nodules. Reference Hauck F, Heine S, Beier R, et al. Chronic granulomatous disease (CGD) mimicking neoplasms: A

2 suspected mediastinal teratoma unmasking as thymic granulomas due to X-linked CGD and 2 related cases. J Pediatr Hematol Oncol (2008); 30(12): Khanna G, Kao SC, Kirby P, Sato Y. Imaging of Chronic Granulomatous Disease in Children. Radiographics (2005); 25:

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