Elwood, a 20 year old criminal justice major, had a summer job working with a ga

Question

Elwood, a 20 year old criminal justice major, had a summer job working with a gardening crew. His job was to spread bark mulch in garden beds. At the end of August he rapidly developed a severe shortness of breath, a persistent cough and chest pain. Because of impending respiratory failure he was admitted to the hospital. A radiological examination of Elwood's chest was performed, and revealed the presence of large "cotton ball densities in both lungs (blue arrows in x-ray). One of these lesions was aspirated with a fine needle and when the aspirate was stained numerous aspergillus hypae were seen. A culture of the aspirate yielded Aspergulus fumagatis Elwood was started on intravenous amphotericin B and assisted mechanical ventilation through a tracheotomy. He slowly improved over the course of two months. During his time in the hospital, he contracted two further respiratory infections with Pseudomonas aeruginosa and Streptococcus faecals. These infections were also treated with appropriate antibiotics. & Geha, 2004 At the time of his itial admission to the hospital, Elwood's white blo d cell count was 11,500 cells per ' (normal range is 5,000-10,000). He had 65% neutrophils, 30% lymphocytes, and 4% monocytes (this distribution falls in the normal range). Because of his infections, which were highly unusual for a seemingly healthy 20 year old, his serum immunoglobulins were measured. The serum lgG level was 1,650 mg per di (upper limit of normal is 1,500 mg per di). IgM and IgA were in the high normal range at 250 and 175 mg per di respectively. Because no defect was apparent with his humoral immunity, his neutrophil and macrophage function was tested for the ability to reduce the compound nitroblue tetrazolium (NBT)-providing a measure of the ability of these tese e panoe and superoide radicals Elwoods neutrophis were unable o reduce NBT (stained red, Panel A). Elwood had 4 sisters and two brothers. Each were also tested for ability to reduce NBT. One brother and two sisters were able to reduce NBT (turned blue, Panel B). For two of Elwood's sisters, and for his mother, about half of the neutrophils were able to reduce NBT, and half were not (Panel C). Elwood's youngest brother Jake was also unable to reduce NBT (not shown). Jake had had a perirectal abcess during infancy but had otherwise been well. Further tests on Elwood and Jake's neutrophils found hydrogen peroxide production was 0.16 and 0.03 nmol per min per 10% cells (normal value is 6.4 nmol per min per 10 cells). The cytochrome bss content in both brothers was undetectable. Both brothers were started on injections of y interferon

Explanation / Answer

1. Elwood can be suffering from the Chronic granulomatous disease. In this hereditary disease, certain cells of the immune system have difficulty forming the reactive oxygen compounds (most importantly the superoxide radical due to defective phagocyte NADPH oxidase) used to kill certain ingested pathogens, in this case, Apergillus fungus. This was diagnostically confirmed by Nitro blue tetrazolium (NBT test).  When there is an NADPH oxidase defect, the phagocyte is unable to make reactive oxygen species or radicals required for bacterial killing. As a result, bacteria may thrive within the phagocyte. The higher the blue score, the better the cell is at producing reactive oxygen species.

CGD patients are particularly susceptible to fungal infections.

2. Half of the neutrophils are reduced and the other half are not, this suggests that the mother is the carrier of the disease. The disease is x linked. Only females can be X-linked carriers of CGD and they are usually identified because a male member of their family (father, son, brother, cousin, nephew) has been diagnosed with CGD.

3. X-linked CGD (XL-CGD) affects males only. It is passed down from the mother to her son as a result of her carrying a genetic fault on her X chromosome. This defect is not passed from the father to the son as it is X linked and this is the reason doctors did not bother to check Ellwood`s father.

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