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Agents in organic dust: criteria for a causal relationship.

Identification of agents of disease causation in organic dust is complicated by the fact that multiple agents may be involved, and these agents may act in a synergistic or additive fashion and cause a number of conditions resulting from chronic toxic or inflammatory effects. A new systematic approach to evaluating available data for evidence of disease-causing agents in organic dust is proposed. It combines, in a matrix fashion, principles of Koch's postulates, River's postulates, principles of epidemiologic determinants, and weight of evidence theory. By applying these principles in a systematic fashion, the strength of the scientific evidence for a specific agent can objectively be evaluated.

Air Pollutants↗

Congenital hypothalamic hamartoblastoma, hypopituitarism, imperforate anus and postaxial polydactyly--a new syndrome? Part I: clinical, causal, and pathogenetic considerations.

We report on six infants with a neonatally lethal malformation syndrome of hypothalamic hamartoblastoma, postaxial polydactyly, and imperforate anus. Some, but not all, patients had laryngeal cleft, abnormal lung lobulation, renal agenesis and/or renal dysplasia, short 4th metacarpals, nail dysplasia, multiple buccal frenula, hypoadrenalism, microphallus, congenital heart defect, and intrauterine growth retardation. The infants also had hypopituitarism and hypoadrenalism. All were sporadic cases, parents were not consanguineous, chromosomes were apparently normal. Family histories were unremarkable. There was insecticide and/or herbicide exposure in several of the cases, but no exposures were common to all 6 mothers. Five of the patients were born within an 8-month period, but all in different geographic locations. It is postulated that this is a previously apparently unreported syndrome of presently unknown cause.

Anus, Imperforate↗

Fra(2) (q13) and inv(9) (p11q12) in autism: causal relationship?

Twenty individuals with autism or related disorders underwent chromosome analysis and physical examinations with documentation of minor anomalies. Chromosome anomalies were identified in 3: 2 had the heritable folate sensitive fra(2) (q13) site and 1 had an inv(9) (p11q12). No heritable chromosome variants or anomalies were seen in 20 age and sex-matched control individuals. When patients with the fra(2) were excluded from analyses, there was no difference in the frequency of chromosome breaks and/or gaps between the study group and control group. The results of this study suggest that heritable folate sensitive fragile sites and other chromosome variants may be more commonly seen in individuals with autism or related disorders in childhood than in the general population.

Adolescent↗

Causal study of isolated ulnar-fibular deficiency in Hungary, 1975-1984.

A population-based and validated data set of 114 cases with isolated ulnar-fibular deficiency was evaluated in Hungary, 1975-1984. Ulnar-fibular type had the third most common birth prevalence (0.07 per 1000) among isolated congenital limb deficiency types. This type is relatively rarely associated with nonlimb defects, a single limb is affected in two-thirds of cases, nearly all other cases had femur-fibula-ulna (FFU) dysostosis. Upper and lower limbs, right and left sides, are equally affected, however, there is an obvious male excess (71%). Case-control analysis indicated a lower birth weight due to intrauterine growth retardation, higher birth order, lower socioeconomic status of parents, and a more frequent reported subfertility. The family study identified one familial cluster (one siboccurrence) among 331 first-degree relatives.

Abnormalities, Drug-Induced↗

Hemangioma, supraumbilical midline raphé, and coarctation of the aorta with a right aortic arch: single causal entity?

Most congenital cutaneous hemangiomas are a sporadic occurrence. Hemangiomas have been found in association with coarctation of the aorta and a right aortic arch. A separate association has been noted of midline ventral defects with hemangiomas. We report on a patient with multiple hemangiomas, coarctation of the aorta and a right aortic arch, a superaumbilical midabdominal raphé and sternal cleft. Our patient represents an overlap between these two conditions. Review of the literature identified four additional patients with a similar combination of anomalies. The clinical overlap between these 5 patients suggests that they are variants of the same conditions and represent a spectrum of defects that includes hemangiomas, midline ventral defects, aortic arch abnormalities and brain malformation.

Aorta↗

Sex ratio and associated risk factors for 50 congenital anomaly types: clues for causal heterogeneity.

BACKGROUND: Sex ratio (SR) deviations have been reported for many congenital anomalies, but so far no satisfactory explanation for these deviations has been found. The aim of this study was to detect sex-related differences in the association between risk factors and congenital anomalies, and to relate these differences with possibly underlying causes of birth defects. METHODS: Between 1982 and 1999, 1,444,646 newborn infants were examined by the Estudio Colaborativo Latino Americano de Malformaciones Congénitas (ECLAMC) network of South American maternity hospitals. Male relative risks were established for 39,425 infants with 50 selected single anomalies. Associations between male sex and risk factors were identified in nonmalformed infants. In malformed infants, sex-related risk differences were established, and the SR of these infants, with and without associated risk factors, were compared. RESULTS: Infants with neural tube defects (NTDs) and intrauterine growth restriction had a lower SR than those with normal growth, while spina bifida without hydrocephaly (SB[sHy]) was the only NTD subtype without a significant female predominance. Multigravidity lowered the SR of SB(sHy) and HPP (HPP) cases. Increased paternal age inverted the SR of cleft lip (CL) with or without cleft palate (CL[P]) cases from male to female. CONCLUSIONS: The results indicate etiological differences between high and low SB, a stronger relationship between multigravidity and female sex of the offspring than between multigravidity and a specific congenital anomaly, and a possible involvement of dominant mutations for CL(P), as suggested by the association with increased paternal age.

Adult↗

Investigations of the genomic region that contains the clf1 mutation, a causal gene in multifactorial cleft lip and palate in mice.

BACKGROUND: Human nonsyndromic cleft lip and palate, CL(P), is genetically complex, with one contributing gene on chromosome 17q. A potentially homologous gene, clf1 on distal chromosome 11, is part of the digenic cause of the 10-30% CL(P) in the A/WySn mouse strain. Here we report our progress toward identifying the clf1 mutation. METHODS: Transcription from all of the known and predicted genes in the 1.5-Mb candidate region was examined in A/WySn and control (AXB-4/Pgn) ED10-11 embryo heads. The marker haplotype for 28 inbred strains across the clf1 region was obtained. The entire transcripts of Wnt9b and Wnt3 in A/WySn were sequenced. Using long PCR, the genomic region from Wnt3 throughWnt9b was screened in A/WySn for an inserted retrotransposon. RESULTS: Gosr2, Wnt9b, Wnt3, Nsf, Arf2, Crhr1, Mapt, Cdc27, Myl4, Itgb3, chr11_20.152, chr11_20.154, chr11_20.155, and chr11_20.156 are expressed in ED10-11 heads. None is absent or detectably reduced in A/WySn. The ancestral pre-clf1 mutation haplotype was found in CBA/J mice. By a test-cross, CBA/J was confirmed to lack the clf1 mutation. Three single-nucleotide variants in A/WySn (vs. C57BL/6J) were found in each of the 3' untranslated regions (3'UTRs) of Wnt3 and of Wnt9b, respectively; their presence in CBA/J shows that none are the clf1 mutation. An inserted intracisternal A particle (IAP) retrotransposon located 6.6 kb from the 3' end of Wnt9b was found in A/WySn and in all clf1 strains tested. This IAP is absent in C57BL/6J and CBA/J. CONCLUSIONS: The clf1 mutation is a genomic alteration present in A/WySn and absent in the ancestral chromosomal segment in CBA/J. The IAP retrotransposon insertion near Wnt9b in A/WySn fits this criterion; we predict that interference with Wnt9b function by this IAP is the clf1 mutation.

Animals↗

Hypersensitivity symptoms associated with exposure to cellular telephones: no causal link.

The hypothesis that there exist hypersensitive persons who perceive subjective symptoms from radiofrequency (RF) fields emitted by hand held mobile phones (cellular phones) was tested using double blind provocation experiments. We also tested whether sensitive subjects are able to determine whether the phone is on or off by sensing RF fields. The study group consisted of 20 volunteers (13 women and 7 men) who reported themselves as being sensitive to cellular phones. The RF exposure sources were one analogue NMT phone (900 MHz) and two digital GSM phones (900 and 1800 MHz). The duration of a test session was 30 min, and three or four sessions were performed in random order for each subject during 1 day. The subjects were asked to report symptoms or sensations as soon as they perceived any abnormal feelings. In addition, the subjects' blood pressure, heart rate, and breathing frequency were monitored every 5 min. The results of the study indicated that various symptoms were reported, and most of them appeared in the head region. However, the number of reported symptoms was higher during sham exposure than during real exposure conditions. In addition, none of the test persons could distinguish real RF exposure from sham exposure. Hence, we conclude that adverse subjective symptoms or sensations, though unquestionably perceived by the test subjects, were not produced by cellular phones.

Adult↗

Development and progression of aortic valve stenosis: atherosclerosis risk factors--a causal relationship? A clinical morphologic study.

Hospital records of 120 patients undergoing aortic valve replacement were retrospectively reviewed for risk factors associated with early aortic valve replacement. Patients were separated into four groups (rheumatic, congenital bicuspid, degenerative, and miscellaneous) based upon the morphologic etiology of aortic stenosis. Multiple regression analysis was performed using age at surgery as the dependent variable. Independent variables for the study were race, gender, systemic hypertension, total triglyceride level, total serum cholesterol level, tobacco smoking history, diabetes mellitus, and angiographic coronary artery disease. In the rheumatic valve group only race showed a statistically significant risk effect whereas in the congenital bicuspid valve group race, gender, and triglycerides were statistically correlated with age at surgery. In the degenerative valve group gender and smoking were found to be statistically significant risk factors. The establishment of aortic stenosis risk factors might be an indication for clinical trials of risk factor modification in patients with aortic stenosis.

Adult↗