The characteristic clinical heterogeneity of sickle cell anemia (HbSS) may be, in part, a result of its interactions with alpha-thalassemia. Although alpha-thalassemia clearly affects some hematologic features of HbSS, its role in modulating the vasoocclusive severity of disease is not clear. To further explore this relationship, we examined the incidence of painful episodes, acute chest syndrome, aseptic bone necrosis, and leg ulcers in 3 patient groups with sickle cell disease: (1) 2,147 patients over age 2 yr, stratified according to mean corpuscular volume (MCV); (2) 183 patients selected on the basis of microcytosis and elevated HbA2, on whom globin biosynthesis studies were done; and (3) 125 patients who had alpha-globin genotype assigned by restriction endonuclease gene mapping. When patients were stratified by MCV, there was a reciprocal relationship between HbA2 levels and MCV, reflecting the presence of patients with beta o and alpha- thalassemia in the low MCV groups. The erythrocyte indices and HbA2 levels in patients classified as HbSS-alpha-thalassemia, by either globin synthesis studies or gene mapping, were very similar to those previously reported by others. Neither microcytosis, beta o, or alpha- thalassemia appeared to provide any clear protection from the vasoocclusive complication evaluated, and the prevalence of aseptic necrosis was increased in patients with microcytosis over age 20 yr and in groups with alpha-thalassemia. The effects of a reduced MCV and mean corpuscular hemoglobin concentration (MCHC), of possible benefit by themselves, when accompanied by a reduction in hemolysis and rise in hemoglobin concentration, as in HbSS-alpha-thalassemia, may cause sufficient rise in blood viscosity in critical vascular beds to impair blood flow and negate any amelioration of vasoocclusive complications in HbSS.

The uniformly negative results with use of highly sensitive methods are in contrast to much of the published literature. Probing of PBMCs for the genes of C. pneumoniae does not appear useful as a noninvasive way of detecting the presence of C. pneumoniae in atheromatous lesions.

Both infectious and non-infectious forms of uveitis occur in individuals who are infected with human immunodeficiency virus and have preserved or restored peripheral CD4+ T cell levels. Individuals who are human immunodeficiency virus-positive and present with uveitis should be evaluated in the same way all patients with uveitis are assessed.

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Less than 20% of infectious diseases consultants work in hospitals that routinely employ decolonization therapy for individuals with staphylococcal carriage undergoing elective surgical procedures or for infection control efforts to limit nosocomial transmission of methicillin-resistant Staphylococcus aureus (MRSA). However, infectious diseases consultants frequently encounter patients with recurrent MRSA furunculosis and attempt to decolonize them.