Secondary Immunodeficiencies

By Dr. Vishaal Bhat on Tuesday 22 December 2009 with 0 comments



1. Neutropenia Usually due to cancer chemotherapy or underlying immunological malignancies, neutopenia can predispose to severe infections when the neutrophil count is < 1000/mm3 and especially when < 500/mm3Dental work, other than to treat odontogenic infections, should be postponed until the neutrophil count exceeds 1000/mm3Cancer chemotherapy and radiation therapy produce a dose-dependent, predictable mucositis.
2. Cellular Immune Dysfunction
a) Prednisone This commonly prescribed anti-inflammatory/ immunosuppressive corticosteroid has a significantly immunosuppressive effect at continuous doses > 10 mg (> 2 tablets) per day.
b) HIV Infection The natural history of this disease involves a complex interplay between viral replication and immunological defenses. The average time (without therapy) from infection with HIV to an AIDS-defining illness is 10 years. The degree of immunosuppression correlates inversely to the CD4 cell count.
A person with a CD4 count > 500/mm3 has essentially normal immunity.

At CD4 counts of 200-499/mm3, susceptibility is markedly increased to such infections as Streptococcus pneumoniae pneumonia, pulmonary tuberculosis, Kaposi's sarcoma (due to human herpes virus 8), shingles (recurrent varicella-zoster), mucocutaneous Candida (vaginitis, thrush), acute cryptosporidiosis and oral hairy leukoplakia.



At CD4 counts of < 200/mm3, the patient becomes susceptible to Pneumocystis carinii pneumonia, Candida esophagitis, disseminated/ chronic herpes simplex, miliary/ extrapulmonary tuberculosis, disseminated dimorphic fungal infections (Cryptococcus neoformans, Coccidioides immitis [SW USA], Histoplasma capsulatum), toxoplasmosis, chronic cryptosporidiosis, microsporidiosis and progressive multifocal leukoencephalopathy.



At CD4 counts of < 50/mm3, the patient becomes susceptible to reactivated cytomegalovirus and Mycobactenum avium complex infections.

3. Metabolic diseases Uremia and diabetes mellitus.

4. Splenectomy Predisposes to sepsis from encapsulated bacteria, particularly Streptococcus pneumoniae

5. Any chronic, debilitating illness, presence of foreign bodies, invasive procedures, malnutrition,

6. Loss of the gag reflex Predisposes to aspiration and thence pneumonia

Category: Microbiology Notes

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