The Phenotypic Spectrum of COL4A3 Heterozygotes

Introduction

The penetrance and phenotypic spectrum of autosomal dominant Alport Syndrome (ADAS), affecting 1 in 106, remains understudied.

Methods

Using data from 174,418 participants in the Geisinger MyCode/DiscovEHR study, an unselected health system-based cohort with whole exome sequencing, we identified 403 participants who were heterozygous for likely pathogenic COL4A3 variants. Phenotypic data was evaluated using International Classification of Diseases (ICD) codes, laboratory data, and chart review. To evaluate the phenotypic spectrum of genetically-determined ADAS, we matched COL4A3 heterozygotes 1:5 to nonheterozygotes using propensity scores by demographics, hypertension, diabetes, and nephrolithiasis.

Results

COL4A3 heterozygotes were at significantly increased risks of hematuria, decreased estimated glomerular filtration rate (eGFR), albuminuria, and kidney failure (P < 0.05 for all comparisons) but not bilateral sensorineural hearing loss (P = 0.9). Phenotypic severity was more severe for collagenous domain glycine missense variants than protein truncating variants (PTVs). For example, patients with Gly695Arg (n = 161) had markedly increased risk of dipstick hematuria (odds ratio [OR] 9.50; 95% confidence interval [CI]: 6.32, 14.28) and kidney failure (OR 7.02; 95% CI: 3.48, 14.16) whereas those with PTVs (n = 119) had moderately increased risks of dipstick hematuria (OR 1.64; 95% CI: 1.03, 2.59) and kidney failure (OR 3.44; 95% CI: 1.28, 9.22). Less than a third of patients had albuminuria screening completed, and fewer than 1 of 3 were taking inhibitors of the renin-angiotensin-aldosterone system.

Conclusion

This study demonstrates a wide spectrum of phenotypic severity in ADAS due to COL4A3 with phenotypic variability by genotype. Future studies are needed to evaluate the impact of earlier diagnosis, appropriate evaluation, and treatment of ADAS.

The Phenotypic Spectrum of COL4A3 Heterozygotes

Most data on Alport Syndrome (AS) due to COL4A3 are limited to families with autosomal recessive AS or severe manifestations such as focal segmental glomerulosclerosis (FSGS). Using data from 174,418 participants in the Geisinger MyCode/DiscovEHR study, an unselected health system-based cohort with whole exome sequencing, we identified 403 participants (0.2%) who were heterozygous for likely pathogenic COL4A3 variants. Phenotypic data was evaluated using International Classification of Diseases (ICD) codes, laboratory data, and chart review. To evaluate the phenotypic spectrum of genetically-determined autosomal dominant AS, we matched COL4A3 heterozygotes 1:5 to non-heterozygotes using propensity scores by demographics, hypertension, diabetes, and nephrolithiasis. COL4A3 heterozygotes were at significantly increased risks of hematuria, decreased estimated glomerular filtration rate (eGFR), albuminuria, and end-stage kidney disease (ESKD) (p<0.05 for all comparisons) but not bilateral sensorineural hearing loss (p=0.9). Phenotypic severity tended to be more severe among patients with glycine missense variants located within the collagenous domain. For example, patients with Gly695Arg (n=161) had markedly increased risk of dipstick hematuria (OR 9.47, 95% CI: 6.30, 14.22) and ESKD diagnosis (OR 7.01, 95% CI: 3.48, 14.12) whereas those with PTVs (n=119) had moderately increased risks of dipstick hematuria (OR 1.63, 95% CI: 1.03, 2.58) and ESKD diagnosis (OR 3.43, 95% CI: 1.28, 9.19). Less than a third of patients had albuminuria screening completed, and fewer than 1/3 were taking inhibitors of the renin-angiotensin-aldosterone system (RAASi). Future studies are needed to evaluate the impact of earlier diagnosis, appropriate evaluation, and treatment of ADAS.

Exome Sequencing of a Clinical Population for Autosomal Dominant Polycystic Kidney Disease

IMPORTANCE

Most studies of autosomal dominant polycystic kidney disease (ADPKD) genetics have used kidney specialty cohorts, focusing on PKD1 and PKD2. These can lead to biased estimates of population prevalence of ADPKD-associated gene variants and their phenotypic expression.

OBJECTIVE

To determine the prevalence of ADPKD and contributions of PKD1, PKD2, and other genes related to cystic kidney disease in a large, unselected cohort.

DESIGN, SETTING, AND PARTICIPANTS

This retrospective observational study used an unselected health system-based cohort in central and northeast Pennsylvania with exome sequencing (enrolled from 2004 to 2020) and electronic health record data (up to October 2021). The genotype-first approach included the entire cohort and the phenotype-first approach focused on patients with ADPKD diagnosis codes, confirmed by chart and imaging review.

EXPOSURES

Loss-of-function (LOF) variants in PKD1, PKD2, and other genes associated with cystic kidney disease (ie, ALG8, ALG9, DNAJB11, GANAB, HNF1B, IFT140, SEC61B, PKHD1, PRKCSH, SEC63); likely pathogenic missense variants in PKD1 and PKD2.

MAIN OUTCOMES AND MEASURES

Genotype-first analysis: ADPKD diagnosis code (Q61.2, Q61.3, 753.13, 753.12); phenotype-first analysis: presence of a rare variant in PKD1, PKD2, or other genes associated with cystic kidney disease.

RESULTS

Of 174 172 patients (median age, 60 years; 60.6% female; 93% of European ancestry), 303 patients had ADPKD diagnosis codes, including 235 with sufficient chart review data for confirmation. In addition to PKD1 and PKD2, LOF variants in IFT140, GANAB, and HNF1B were associated with ADPKD diagnosis after correction for multiple comparisons. Among patients with LOF variants in PKD1, 66 of 68 (97%) had ADPKD; 43 of 43 patients (100%) with LOF variants in PKD2 had ADPKD. In contrast, only 24 of 77 patients (31.2%) with a PKD1 missense variant previously classified as "likely pathogenic" had ADPKD, suggesting misclassification or variable penetrance. Among patients with ADPKD diagnosis confirmed by chart review, 180 of 235 (76.6%) had a potential genetic cause, with the majority being rare variants in PKD1 (127 patients) or PKD2 (34 patients); 19 of 235 (8.1%) had variants in other genes associated with cystic kidney disease. Of these 235 patients with confirmed ADPKD, 150 (63.8%) had a family history of ADPKD. The yield for a genetic determinant of ADPKD was higher for those with a family history of ADPKD compared with those without family history (91.3% [137/150] vs 50.6% [43/85]; difference, 40.7% [95% CI, 29.2%-52.3%]; P < .001). Previously unreported PKD1, PKD2, and GANAB variants were identified with pedigree data suggesting pathogenicity, and several PKD1 missense variants previously reported as likely pathogenic appeared to be benign.

CONCLUSIONS AND RELEVANCE

This study demonstrates substantial genetic and phenotypic variability in ADPKD among patients within a regional health system in the US.

Electronic health record analysis identifies kidney disease as the leading risk factor for hospitalization in confirmed COVID-19 patients

BACKGROUND

Empirical data on conditions that increase risk of coronavirus disease 2019 (COVID-19) progression are needed to identify high risk individuals. We performed a comprehensive quantitative assessment of pre-existing clinical phenotypes associated with COVID-19-related hospitalization.

METHODS

Phenome-wide association study (PheWAS) of SARS-CoV-2-positive patients from an integrated health system (Geisinger) with system-level outpatient/inpatient COVID-19 testing capacity and retrospective electronic health record (EHR) data to assess pre-COVID-19 pandemic clinical phenotypes associated with hospital admission (hospitalization).

RESULTS

Of 12,971 individuals tested for SARS-CoV-2 with sufficient pre-COVID-19 pandemic EHR data at Geisinger, 1604 were SARS-CoV-2 positive and 354 required hospitalization. We identified 21 clinical phenotypes in 5 disease categories meeting phenome-wide significance (P<1.60x10-4), including: six kidney phenotypes, e.g. end stage renal disease or stage 5 CKD (OR = 11.07, p = 1.96x10-8), six cardiovascular phenotypes, e.g. congestive heart failure (OR = 3.8, p = 3.24x10-5), five respiratory phenotypes, e.g. chronic airway obstruction (OR = 2.54, p = 3.71x10-5), and three metabolic phenotypes, e.g. type 2 diabetes (OR = 1.80, p = 7.51x10-5). Additional analyses defining CKD based on estimated glomerular filtration rate, confirmed high risk of hospitalization associated with pre-existing stage 4 CKD (OR 2.90, 95% CI: 1.47, 5.74), stage 5 CKD/dialysis (OR 8.83, 95% CI: 2.76, 28.27), and kidney transplant (OR 14.98, 95% CI: 2.77, 80.8) but not stage 3 CKD (OR 1.03, 95% CI: 0.71, 1.48).

CONCLUSIONS

This study provides quantitative estimates of the contribution of pre-existing clinical phenotypes to COVID-19 hospitalization and highlights kidney disorders as the strongest factors associated with hospitalization in an integrated US healthcare system.

ALG9 Mutation Carriers Develop Kidney and Liver Cysts

BACKGROUND

Mutations in PKD1 or PKD2 cause typical autosomal dominant polycystic kidney disease (ADPKD), the most common monogenic kidney disease. Dominantly inherited polycystic kidney and liver diseases on the ADPKD spectrum are also caused by mutations in at least six other genes required for protein biogenesis in the endoplasmic reticulum, the loss of which results in defective production of the PKD1 gene product, the membrane protein polycystin-1 (PC1).

METHODS

We used whole-exome sequencing in a cohort of 122 patients with genetically unresolved clinical diagnosis of ADPKD or polycystic liver disease to identify a candidate gene, ALG9, and in vitro cell-based assays of PC1 protein maturation to functionally validate it. For further validation, we identified carriers of ALG9 loss-of-function mutations and noncarrier matched controls in a large exome-sequenced population-based cohort and evaluated the occurrence of polycystic phenotypes in both groups.

RESULTS

Two patients in the clinically defined cohort had rare loss-of-function variants in ALG9, which encodes a protein required for addition of specific mannose molecules to the assembling N-glycan precursors in the endoplasmic reticulum lumen. In vitro assays showed that inactivation of Alg9 results in impaired maturation and defective glycosylation of PC1. Seven of the eight (88%) cases selected from the population-based cohort based on ALG9 mutation carrier state who had abdominal imaging after age 50; seven (88%) had at least four kidney cysts, compared with none in matched controls without ALG9 mutations.

CONCLUSIONS

ALG9 is a novel disease gene in the genetically heterogeneous ADPKD spectrum. This study supports the utility of phenotype characterization in genetically-defined cohorts to validate novel disease genes, and provide much-needed genotype-phenotype correlations.

Genetic variants help define the role of the MC4R C-terminus in signaling and cell surface stability

Screening 92,445 subjects in the Geisinger-Regeneron DiscovEHR cohort, we identified 5 patients heterozygous for nonsense mutations causing early terminations at Glu307 or Leu328 on the C-terminus of melanocortin 4 receptor (MC4R). Two Q307Ter carriers are severely obese (BMI > 40), while one is overweight (BMI > 25). One L328Ter carrier is overweight and the other is lean. Pedigree analysis for two Q307Ter carriers shows segregation of the variant with higher BMI. Functionally, MC4R(Q307Ter) eliminated receptor surface expression and signaling, while MC4R(L328Ter) functioned like the wild-type receptor. MC4R(Q307Ter) is therefore a loss of function (LOF) variant and the region between the two truncation sites identified in our patients is critical to MC4R function. Truncating MC4R at various C-terminal positions between these two variant sites, we find that cysteine318 sits at a critical junction for receptor trafficking and function. We show that MC4R is lipid modified at cysteine318 and cysteine319. Therefore, truncation early in the MC4R C-terminus results in haploinsufficiency in humans while truncation after the first lipid-modification site is well tolerated. MC4R haploinsufficiency clearly segregates with higher BMI; however, severe obesity is not fully penetrant even in MC4R LOF carriers, suggesting critical roles for environmental and lifestyle factors in MC4R monogenic obesity.

Long-term weight-loss in gastric bypass patients carrying melanocortin 4 receptor variants

BACKGROUND

The melanocortin 4 receptor (MC4R) critically regulates feeding and satiety. Rare variants in MC4R are predominantly found in obese individuals. Though some rare variants in MC4R discovered in patients have defects in localization, ligand binding and signaling to cAMP, many have no recognized defects.

SUBJECTS/METHODS

In our cohort of 1433 obese subjects that underwent Roux-en-Y Gastric Bypass (RYGB) surgery, we found fifteen variants of MC4R. We matched rare variant carriers to patients with the MC4R reference alleles for gender, age, starting BMI and T2D to determine the variant effect on weight-loss post-RYGB. In vitro, we determined expression of mutant receptors by ELISA and western blot, and cAMP production by microscopy.

RESULTS

While carrying a rare MC4R allele is associated with obesity, carriers of rare variants exhibited comparable weight-loss after RYGB to non-carriers. However, subjects carrying three of these variants, V95I, I137T or L250Q, lost less weight after surgery. In vitro, the R305Q mutation caused a defect in cell surface expression while only the I137T and C326R mutations showed impaired cAMP signaling. Despite these apparent differences, there was no correlation between in vitro signaling and pre- or post-surgery clinical phenotype.

CONCLUSIONS

These data suggest that subtle differences in receptor signaling conferred by rare MC4R variants combined with additional factors predispose carriers to obesity. In the absence of complete MC4R deficiency, these differences can be overcome by the powerful weight-reducing effects of bariatric surgery. In a complex disorder such as obesity, genetic variants that cause subtle defects that have cumulative effects can be overcome after appropriate clinical intervention.

A conserved mechanism for gating in an ionotropic glutamate receptor

Ionotropic glutamate receptor (iGluR) channels control synaptic activity. The crystallographic structure of GluA2, the prototypical iGluR, reveals a clamshell-like ligand-binding domain (LBD) that closes in the presence of glutamate to open a gate on the pore lining α-helix. How LBD closure leads to gate opening remains unclear. Here, we show that bending the pore helix at a highly conserved alanine residue (Ala-621) below the gate is responsible for channel opening. Substituting Ala-621 with the smaller more flexible glycine resulted in a basally active, nondesensitizing channel with ∼39-fold increase in glutamate potency without affecting surface expression or binding. On GluA2(A621G), the partial agonist kainate showed efficacy similar to a full agonist, and competitive antagonists CNQX and DNQX acted as a partial agonists. Met-629 in GluA2 sits above the gate and is critical in transmitting LBD closure to the gate. Substituting Met-629 with the flexible glycine resulted in reduced channel activity and glutamate potency. The pore regions in potassium channels are structurally similar to iGluRs. Whereas potassium channels typically use glycines as a hinge for gating, iGluRs use the less flexible alanine as a hinge at a similar position to maintain low basal activity allowing for ligand-mediated gating.

Engineering biodiversity with type II polyketide synthase genes

A very important task in the ongoing search for new clinically useful drugs is the generation of large numbers of structurally diverse compounds. The emerging field of combinatorial biosynthesis, in which nature's chemical capabilities are exploited in a combinatorial 'mix-and-match' fashion, has generated libraries of novel molecules representing great structural diversity which are not available naturally or readily generated through (combinatorial) synthesis. Novel polyketides have been generated by manipulating type II iterative polyketide synthase (PKS) systems that express a variety of combinations of a minimal PKS with ketoreductases, cyclases, and other tailoring enzymes, resulting in a set of design rules to rationally engineer new metabolites. Engineering studies with the Streptomyces coelicolor whiE (spore pigment) and the 'Streptomyces maritimus' enterocin type II PKS provide additional insight on designing diverse assemblies of aromatic, as well as nonaromatic, polyketides.

Cloning, sequencing and analysis of the enterocin biosynthesis gene cluster from the marine isolate 'Streptomyces maritimus': evidence for the derailment of an aromatic polyketide synthase

BACKGROUND

Polycyclic aromatic polyketides, such as the tetracyclines and anthracyclines, are synthesized by bacterial aromatic polyketide synthases (PKSs). Such PKSs contain a single set of iteratively used individual proteins for the construction of a highly labile poly-beta-carbonyl intermediate that is cyclized by associated enzymes to the core aromatic polyketide. A unique polyketide biosynthetic pathway recently identified in the marine strain 'Streptomyces maritimus' deviates from the normal aromatic PKS model in the generation of a diverse series of chiral, non-aromatic polyketides.

RESULTS

A 21.3 kb gene cluster encoding the biosynthesis of the enterocin and wailupemycin family of polyketides from 'S. maritimus' has been cloned and sequenced. The biosynthesis of these structurally diverse polyketides is encoded on a 20 open reading frames gene set containing a centrally located aromatic PKS. The architecture of this novel type II gene set differs from all other aromatic PKS clusters by the absence of cyclase and aromatase encoding genes and the presence of genes encoding the biosynthesis and attachment of the unique benzoyl-CoA starter unit. In addition to the previously reported heterologous expression of the gene set, in vitro and in vivo expression studies with the cytochrome P-450 EncR and the ketoreductase EncD, respectively, support the involvement of the cloned genes in enterocin biosynthesis.

CONCLUSIONS

The enterocin biosynthesis gene cluster represents the most versatile type II PKS system investigated to date. A large series of divergent metabolites are naturally generated from the single biochemical pathway, which has several metabolic options for creating structural diversity. The absence of cyclase and aromatase gene products and the involvement of an oxygenase-catalyzed Favorskii-like rearrangement provide insight into the observed spontaneity of this pathway. This system provides the foundation for engineering hybrid expression sets in the generation of structurally novel compounds for use in drug discovery.

Significance of the anti-E2 response in self-limited and chronic hepatitis C virus infections in chimpanzees and in humans

To determine whether there was a correlation between the kinetics or frequency of antibody to mammalian-derived hepatitis C virus (HCV) second envelope protein (E2) and development of chronicity or self-limitation of HCV infections, serial sera were examined for anti-E2, anti-HCV with confirmation with Matrix 2.0 (Abbott Laboratories, Abbott Park, IL), and reverse transcriptase-polymerase chain reaction (RT-PCR) from 6 cases of self-limited infection and 6 cases of chronic infection in chimpanzees, and from 5 cases of self-limited infection and 3 cases of chronic infection in patients. Anti-E2 developed earlier, more frequently, and to higher titer in chimpanzees and patients who were developing chronic infection than in those with self-limited infections. Thus anti-E2 is unlikely to play a role in self-limitation of the infection. However, long-term persistence of anti-E2 correlates with chronic infection. There was little or no correlation between the timing of development of anti-E2 and anti-HCV.

Direct evidence that the rifamycin polyketide synthase assembles polyketide chains processively

The assembly of the polyketide backbone of rifamycin B on the type I rifamycin polyketide synthase (PKS), encoded by the rifA-rifE genes, is terminated by the product of the rifF gene, an amide synthase that releases the completed undecaketide as its macrocyclic lactam. Inactivation of rifF gives a rifamycin B nonproducing mutant that still accumulates a series of linear polyketides ranging from the tetra- to a decaketide, also detected in the wild type, demonstrating that the PKS operates in a processive manner. Disruptions of the rifD module 8 and rifE module 9 and module 10 genes also result in accumulation of such linear polyketides as a consequence of premature termination of polyketide assembly. Whereas the tetraketide carries an unmodified aromatic chromophore, the penta- through decaketides have undergone oxidative cyclization to the naphthoquinone, suggesting that this modification occurs during, not after, PKS assembly. The structure of one of the accumulated compounds together with (18)O experiments suggests that this oxidative cyclization produces an 8-hydroxy-7, 8-dihydronaphthoquinone structure that, after the stage of proansamycin X, is dehydrogenated to an 8-hydroxynaphthoquinone.

Ectopic expression of the minimal whiE polyketide synthase generates a library of aromatic polyketides of diverse sizes and shapes

The single recombinant expressing the Streptomyces coelicolor minimal whiE (spore pigment) polyketide synthase (PKS) is uniquely capable of generating a large array of well more than 30 polyketides, many of which, so far, are novel to this recombinant. The characterized polyketides represent a diverse set of molecules that differ in size (chain length) and shape (cyclization pattern). This combinatorial biosynthetic library is, by far, the largest and most complex of its kind described to date and indicates that the minimal whiE PKS does not independently control polyketide chain length nor dictate the first cyclization event. Rather, the minimal PKS enzyme complex must rely on the stabilizing effects of additional subunits (i.e., the cyclase whiE-ORFVI) to ensure that the chain reaches the full 24 carbons and cyclizes correctly. This dramatic loss of control implies that the growing polyketide chain does not remain enzyme bound, resulting in the spontaneous cyclization of the methyl terminus. Among the six characterized dodecaketides, four different first-ring cyclization regiochemistries are represented, including C7/C12, C8/C13, C10/C15, and C13/C15. The dodecaketide TW93h possesses a unique 2,4-dioxaadamantane ring system and represents a new structural class of polyketides with no related structures isolated from natural or engineered organisms, thus supporting the claim that engineered biosynthesis is capable of producing novel chemotypes.

Lack of evidence of hepatitis C infection in 290 blood component recipients, demonstrated by several single-antigen research immunoassays

BACKGROUND

A group of 290 transfusion recipients enrolled in a prospective study of posttransfusion hepatitis was studied to determine the possibility of previously unrecognized hepatitis C virus (HCV) transmission.

STUDY DESIGN AND METHODS

Before and after transfusion, blood specimens that were negative in first-generation enzyme immunoassay (EIA) were tested by current commercial EIAs, several single-antigen research EIAs, and supplemental tests.

RESULTS

Current second- and third-generation EIAs identified five subjects (1.7% of total) who had chronic hepatitis C before transfusion. Twenty additional sera had some reactivity with research EIAs. However, those results were the same before and after transfusion (n = 7), had reverted to partially reactive or nonreactive (n = 8), or could not be confirmed by serologic tests or polymerase chain reaction in follow-up specimens (n = 5).

CONCLUSIONS

Transient or restricted reactivity to HCV antigens measured by more sensitive research EIAs does not seem to correspond to recent HCV transmission by transfusion. Whether such reactivity could reflect remote HCV infection, with the potential for chronic or intermittent viremia, remains to be determined.

Three new omega-cycloheptyl fatty acids from Alicyclobacillus cycloheptanicus and their biosynthetic interrelationships

Three minor omega-cycloheptyl fatty acids from Alicyclobacillus cycloheptanicus have been identified as omega-cycloheptylnonanoate, -decanoate, and -alpha-hydroxytridecanoate. The biosynthetic interrelations of these cyclic fatty acids have been studied. 13C-Labeled omega-cycloheptylundecanoate and -alpha-hydroxyundecanoate were converted to omega-cycloheptyldecanoate, which is one carbon shorter in length. alpha-Hydroxylation of omega-cycloheptylundecanate was also observed, but not chain extension to omega-cycloheptyltridecanoate.

Biosynthetic studies on the origin of the cyclohexanecarboxylic acid moiety of ansatrienin A and omega-cyclohexyl fatty acids

Feeding experiments with [2,6,10,10-2H4]chorismate in Streptomyces collinus (ansatrienin A) and Alicyclobacillus acidocaldarius (omega-cyclohexyl fatty acids), and inhibitor experiments with glyphosate in the latter organism, have shown that the biosynthesis of cyclohexanecarboxylic acid branches off from the shikimate pathway at a point prior to enolpyruvylshikimate 3-phosphate, either at shikimate or shikimate 3-phosphate.

Nursing research: quality of life and perceived health in the elderly

1. Studies have shown that self-perceived health is significantly related to quality of life for older persons. 2. Terminology regarding quality of life and perceived health was found to be inconsistent in the gerontological nursing research reviewed. 3. Outcomes of the research related to quality of life and perceived health fell into three basic categories: predictors found, relationships found, and no relationships found. 4. More experimental research, more replication of research, more research on older males, more use of nursing theory as a framework for research, and more multidisciplinary gerontological research may contribute useful knowledge to the nursing discipline.

Transcatheter manipulation of asymmetrically opened titanium Greenfield filters

PURPOSE

The problem of asymmetric opening of the modified hook titanium Greenfield inferior vena cava filter necessitating transcatheter manipulation was evaluated in a retrospective study.

PATIENTS AND METHODS

Titanium Greenfield filters were placed in 166 patients over a 36-month period. The radiographic reports of all patients were reviewed to identify cases in which the filter failed to open symmetrically after deployment and catheter or wire manipulation of the filter was performed. The reports and angiograms from these patients were reviewed with respect to the circumstances surrounding filter placement and methods to achieve more symmetric opening.

RESULTS

Transcatheter manipulation of asymmetrically opened filters was performed in 15 of 166 cases (9%). In 12 of these patients, acceptable and uneventful opening of the filter was achieved with a guide wire, pigtail catheter, or occlusion balloon catheter. In one case manipulation only partly improved orientation of the limbs, while in another case successful manipulation was complicated by distal migration. In the final case, the asymmetric filter covered only part of the lumen of the vena cava despite manipulations and a second filter was placed for optimal caval interruption. No specific cause for incomplete expansion was identified in any case.

CONCLUSION

Marked asymmetry in opening of the modified hook titanium Greenfield filter that warrants manipulation occurs infrequently, but recognition and proper management may be important to ensure optimal caval interruption.

Suspected Marfan Syndrome in a Female Basketball Player

A group of experts met to discuss a case from the University of California, San Diego, School of Medicine. This case conference is part of a series featuring a variety of sports medicine topics.

The effect of daily Hassles of humoral immunity: an interaction moderated by locus of control

Research has shown that stress is associated with depressed cellular immune functioning. Controversy exists as to whether humoral immunity shows a similar depression under stress. Several psychological variables have been found to moderate responses to stress. In particular, an internal locus of control has been correlated with better health. The present study examined the level of salivary immunoglobulin A (IgA) and health locus of control in subjects with high and low stress levels. The Hassles scale was administered to identify two subject groups differing significantly in reported stress levels. Results showed no significant differences between the two groups on salivary IgA. There was a significant negative correlation between IgA and internal locus of control. The direction of this correlation is in contrast with previous findings on internality. The evidence suggests that high internal individuals may be especially vulnerable to high levels of stress, particularly stress that they cannot control. Also, there was a significant difference in IgA levels between females depending on whether they were in the first or the second half of their menstrual cycle. Those in the premenstrual phase had lower IgA levels.

Haemophilus influenzae type b disease after rifampin prophylaxis in a day care center: possible reasons for its failure

Five infants enrolled in a day care center (DCC) developed invasive disease due to Haemophilus influenzae type b during a 25-week period. The isolates from four patients had identical outer membrane proteins and were biotype 1. Although rifampin prophylaxis was recommended on two different occasions, retrospective surveys demonstrated that 39 and 60%, respectively, of infants failed to receive the agent for various reasons. Pharyngeal cultures were obtained from infants, their families and DCC staff after prophylaxis was given the second time. Forty-seven % of DCC infants had positive cultures, and 59% of their households had at least one carrier of the invasive strain. Rifampin prophylaxis administered a third time to infants and members of their households was unsuccessful in eradicating the invasive Haemophilus influenzae type b strain from DCC infants. The possible reasons for failure of rifampin in this DCC outbreak included incomplete understanding by physicians and health department officials of the factors affecting a DCC outbreak of Haemophilus influenzae type b disease and failure properly to implement rifampin prophylaxis to all contacts and the index cases.

Breed-specific dog hypersensitivity in humans

The contribution of allergenic components of dander and serum from individual dog breeds in human hypersensitivity and the different responses to the various breeds in vivo and in vitro were examined. Differences in IgE antibodies directed against 13 individual dog breed danders and five different breed-specific sera were measured in groups sensitive and nonsensitive to dogs by the radioallergosorbent test (RAST). Cross-reactivity between dander extracts and sera was examined by RAST inhibition. Mean RAST binding to dog danders and sera was 15.9% and 14%, respectively, for the dog-sensitive group versus 0.6% for both danders and sera in the nonsensitive group. The mean difference in binding between groups was statistically different for all dander extracts and sera. The variances in binding were statistically greater for danders than sera in six of eight dog-reactive subjects. RAST binding and intradermal skin tests at a 1:10,000 w/v dilution correlated well (p < 0.05) for seven of nine breed-specific extracts. RAST inhibition studies showed that dog serum proteins were relatively poor inhibitors of dander extracts, and vice versa. Variability of skin test and RAST responses to different dog breed dander extracts support the existence of breed-specific allergens.

IgE antibodies to Mycoplasma pneumoniae in asthma and other atopic diseases

IgE antibodies to Mycoplasma pneumoniae antigens were measured by RAST assay in 152 patients with asthma and other IgE and non-IgE mediated diseases. Five patients with asthma and/or atopic dermatitis had highly elevated Mycoplasma RAST binding ratios, p < 0.001. For these five patients the ratios ranged from 1.78 to 4.74. These increased ratios persisted at least two to 16 months in three of four individuals who were evaluated sequentially. RAST inhibition studies using Mycoplasma pneumoniae, Mycoplasma control, Streptococcus MG and viral antigens showed the specificity of binding for M. pneumoniae in these five patients indicating the presence of IgE antibodies to M. pneumoniae.

Protease inhibitor variants in children and young adults with chronic asthma

The results of systematic medical histories and pulmonary function tests on 26 children and young adults, 10 with Pi variant alpha1-antitrypsin phenotypes and 16 Pi normals, are reported. These subjects were selected from 57 consecutive patients who had chronic asthma. The incidence of Pi variants was 20.4% among 46 Caucasian subjects (ages seven to 21 years). The Pi variant patients required more bronchodilators and long-term corticosteroid therapy. Among the parents and siblings, 50% of those with abnormal Pi type had chronic obstructive lung disease. Grandparents of the Pi abnormal probands had greater incidence of chronic obstructive lung disease (P less than 0.05). Baseline specific airways conductance and maximal midexpiratory flow rates did not discriminat between the two groups. However, bronchodilator inhalation showed the Pi variant group to be significantly less responsive than the Pi normal group. Pi heterozygous state, particularly Pi MZ, should be considered when a young person with chronic asthma is unresponsive to adequate doses of bronchodilators and needs prolonged use of corticosteroids.

Chronic rhinitis in the pre-school child

The etiologic role of atopy in chronic rhinitis in 40 infants and pre-school children was investigated and the long-term effectiveness and safety of promethazine studied during six to 48 months. Twenty children were clearly atopic and 16 were not. Four had incomplete laboratory evidence of atopy. In addition to clinical histories and physical findings, the subjects were evaluated by skin tests for common allergens. RAST tests, total IgE levels and absolute eosinophil counts. Promethazine in doses of 3 to 12 mg/kg/day (mean 8 mg) was administered in divided doses, four times a day for perennial rhinitis and on "as required" basis for recurrent and seasonal rhinitis. Side effects included drowsiness and irritability, which led to discontinuance of promethazine in one subject. There was no laboratory evidence of hematologic, renal or hepatic abnormalities. Promethazine was found to be an effective agent for symptom-control of chronic rhinitis in the pre-school child.

Hypersensitivity to milk and egg white. Skin tests, rast results and clinical intolerance

Prick tests to milk and egg white were compared to clinical histories of sensitivity to these foods. Seventeen RAST-positive versus 17 RAST-negative controls were used. All 34 children and young adults were selected because they had atopic respiratory and/or dermal manifestations. Atopic eczema manifestations were present in 11 of the RAST-postive subjects and in two of the controls. Of these, nine had past history of egg white intolerance. Egg white challenge was associated with dermal reactions as follows: eczema in two, urticaria in two and angioedema in two. Positive clinical histories compared favorably (p less than 0.001) with prick tests for egg white but poorly (p greater than 0.05) for milk. Similarly, positive clinical histories compared significantly (p less than 0.001) with RAST for egg white but poorly (p greater than 0.05) for milk.

A comparative study of allergens of canine origin

Among 115 children and young adults studied, 52 had current and 25 had past household exposure to dogs, totaling 77 subjects. Of 53 with clinical hypersensitivity to dog, 32 had a history of exposure, 34 positive cutaneous reactions and 15 RAST positive results. Of 62 without clinical hypersensitivity, 45 had a history of household exposure, 24 positive cutaneous reactions and 6 RAST positive results. Cutaneous tests were not done on seven individuals. The major type of clinical symptomatology to dogs was ocular and nasal, 40 of 53. Thirty-two of 53 patients developed asthma exacerbations alone, or in combination with other manifestations, upon dog exposure. Dermal reactions were urticaria is six and contact eczema in two subjects. RAST inhibition results suggested that in vitro testing may be more useful when allergens from specific dog breed extracts are characterized.

Ectopic glial tissue in the occipital scalp

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