Heterogeneity of genetic modifiers ensures normal cardiac development.

BACKGROUND: Mutations of the transcription factor Nkx2-5 cause pleiotropic heart defects with incomplete penetrance. This variability suggests that additional factors can affect or prevent the mutant phenotype. We assess here the role of genetic modifiers and their interactions. METHODS AND RESULTS: Heterozygous Nkx2-5 knockout mice in the inbred strain background C57Bl/6 frequently have atrial and ventricular septal defects. The incidences are substantially reduced in the Nkx2-5(+/-) progeny of first-generation (F1) outcrosses to the strains FVB/N or A/J. Defects recur in the second generation (F2) of the F1 X F1 intercross or backcrosses to the parental strains. Analysis of >3000 Nkx2-5(+/-) hearts from 5 F2 crosses demonstrates the profound influence of genetic modifiers on disease presentation. On the basis of their incidences and coincidences, anatomically distinct malformations have shared and unique modifiers. All 3 strains carry susceptibility alleles at different loci for atrial and ventricular septal defects. Relative to the other 2 strains, A/J carries polymorphisms that confer greater susceptibility to atrial septal defect and atrioventricular septal defects and C57Bl/6 to muscular ventricular septal defects. Segregation analyses reveal that > or = 2 loci influence membranous ventricular septal defect susceptibility, whereas > or = loci and at least 1 epistatic interaction affect muscular ventricular and atrial septal defects. CONCLUSIONS: Alleles of modifier genes can either buffer perturbations on cardiac development or direct the manifestation of a defect. In a genetically heterogeneous population, the predominant effect of modifier genes is health. (Circulation. 2010;121:1313-1321.)

HIV-related pneumonia care in older patients hospitalized in the early HAART era.

Age-related variations in care have been identified for HIV-associated Pneumocystis carinii pneumonia (PCP) in both the 1980s and 1990s. We evaluated if age-related variations affected all aspects of HIV-specific and non-HIV-specific care for HIV-infected individuals with PCP or community-acquired pneumonia (CAP), or whether age-related variations were primarily limited to HIV-specific aspects of care. Subjects were HIV-infected persons with PCP (n = 1855) or CAP (n = 1415) hospitalized in 8 cities from 1995 to 1997. Nine percent of our study patients had received protease inhibitors and 39% had received any type of antiretroviral therapy prior to hospitalization. Data were abstracted from medical records and included severity of illness, HIV-specific aspects of care (initiation of PCP medications), general measures of care [initiation of CAP medications, intubation, and intensive care units (ICU)], and inpatient mortality. Compared to younger patients, pneumonia patients 50 years of age or older were significantly more likely to: be severely ill (PCP, 20.4% vs. 10.4%; CAP, 27.5% vs. 14.9%; each p = 0.001), receive ICU care (PCP, 22.0% vs. 12.8%, p = 0.002; CAP: 15.1% vs. 9.4%; p = 0.02), and be intubated (PCP, 14.6% vs. 8.4%, p = 0.01; CAP, 9.9% vs. 5.6%, p = 0.03). Compared to younger patients, older patients (>/=50 years) had similar rates of timely medications for CAP (48.5% vs. 50.8%) but had lower rates of receiving anti-PCP medications (85.8% vs. 92.9%, p = 0.002). Differences by age in timely initiation of PCP medications, ICU use, and intubation were limited to the nonseverely ill patients. Older hospitalized patients were more likely to die (PCP, 18.3% vs. 10.4%; CAP, 13.4% vs. 8.5%; each p < 0.05). After adjustment for disease severity and timeliness of antibiotic use, mortality rates were similar for both age groups. Physicians should develop strategies that increase awareness of the possibility of HIV infection in older individuals.