Biomedical subjects
Publications and source records attributed to L J Sheffield.
We report here a father and daughter with digital abnormalities, nasolacrimal duct obstruction, and variable alopecia. The father had a cleft lip and palate and the daughter had choanal atresia. We propose they both have the EEC syndrome and show the variable expressivity of this disorder. Choanal atresia has not been previously reported in this condition.
A family in which the gene for myotonic dystrophy is segregating was tested with a DNA probe to the apolipoprotein-C2 (APOC2) gene. The APOC2 gene is linked closely to the myotonic dystrophy (DM) gene and can be used as a marker to follow the transmission of the DM gene within families. Results from DNA-marker studies were combined with information from clinical, ophthalmological and electromyographic examinations, with age-dependent penetrance and a recombinant frequency of 4% between the genes for myotonic dystrophy and apolipoprotein C2 being taken into account. The chance that an individual had inherited the gene for myotonic dystrophy was determined by means of the computer program, LINKAGE. This analysis altered dramatically the assessed risk that certain individuals in the family were carrying the DM gene. For four individuals in the family, the previous risks of 50% for each member were reduced to 0.9%, 0.9% and 0.2%, respectively, in three cases and increased to 91% in the fourth case. The importance of a complete clinical evaluation of potential gene carriers who donate blood for a DNA-linkage study is stressed.
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Thirty-four Duchenne and Becker muscular dystrophy families were initially ascertained from South Australia. These have been tested systematically with the DNA probes XJ1.1 and pERT87-15. DNA results from 21 informative families have been combined with results of CK testing. Pedigree analysis was carried out using the computer program LINKAGE to provide risk figures to potential female carriers. This simple approach separated potential carriers into low or high risk classes (familial cases) or low or moderate risk classes (isolated cases). No prenatal diagnoses were carried out. The detection of deletions in two probands out of 34 makes possible definitive prenatal diagnosis in those families. For the remaining families, prenatal diagnosis could only be offered in terms of a probability statement after linkage analysis. Risk figures presented from hypothetical pedigrees demonstrated that prenatal diagnosis by linkage usually provided reasonable reliability only where informative flanking markers are used.
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A genetic follow-up study has been performed of 64 infants who were diagnosed as having Pierre Robin complex over a 23-year period in South Australia. Patients and their families were contacted, family history was obtained, and physical examinations were performed with an aim to detect heterogeneity and establish recurrence risks. In 16 deceased patients, detailed autopsy reports allowed the conclusion that 12 (70%) had an underlying syndrome. Twelve of the 47 living patients (26%) were diagnosed as having an underlying syndrome, the most common of which was Stickler syndrome (6 cases). In most cases separation of syndromic cases from the nonsyndromic cases was possible in the neonatal period. In the 34 patients without an underlying syndrome, study of pregnancy and birth details did not reveal any distinctive etiologic factors. There was no recurrence in sibs of this group of patients with nonsyndromic Pierre Robin complex.
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Five family members with distal arthrogryposis in two generations are reported. Cleft lip and palate, micrognathia, ptosis, webbed neck, kyphoscoliosis, and short stature are seen in one or more affected family members. All individuals with distal arthrogryposis also have trismus. This family does not fit any of the recently proposed five subcategories of type II distal arthrogryposis, nor does it fit any other recognized autosomal dominant condition with distal contractures.
Two cousins with an unbalanced chromosome translocation (partial trisomy 3p) are described. Both children have a clinically recognizable syndrome of square facies with prominent cheeks, narrow bitemporal regions, psychomotor retardation and congenital heart disease. Extended family studies showed one other individual proven to have partial trisomy 3p karyotype, two retarded individuals with congenital heart disease who probably had it, and 14 balanced carriers of the translocation t(1;3)(q43;p21). This report confirms the characteristic clinical appearance of affected individuals and emphasizes the frequency in which congenital heart disease is the presenting feature of partial trisomy 3p. An additional 22 cases of partial 3p trisomy are reviewed.
The drug combination Debendox has been very widely used for the treatment of nausea and vomiting in pregnancy. Recently its manufacturer ceased world-wide production owing to the increasing costs of litigation associated with claims of teratogenicity. Teratogenicity claims were widespread in the media but the overwhelming scientific evidence was that Debendox was not teratogenic. In the interests of preventing other drugs (and drug companies) being subjected to similarly unfounded claims, the literature relating to the effects of Debendox on the fetus has been reviewed and evaluated against well known epidemiological principles of establishing causality. This evaluation consistently demonstrates that Debendox is not in fact teratogenic. It is recommended that appropriate professional bodies be more aware of the criteria by which causation is established and be prepared publicly to state their considered views of the effects of particular drugs in pregnancy.
This work discusses how Student's t-tests might still be validly applied to medical data that may violate the usual statistical assumptions. Here the one sample t-test, which includes as a special case the paired comparisons t-test, is treated in detail. Practical "rules-of-thumb" are given, along with their applications to various examples, so that readers will easily be able to use them on their own data sets.
The rationale of calculating predictive values to interpret the amniotic fluid alpha-fetoprotein (AFP) test has been examined and applied to amniotic fluid AFP testing from one Canadian center. Such predictive value ccalculations may be misleading if they fail to make use of the actual magnitude of the test result or the results of other investigations. The alculation of predictive values has thus been extended to take into account magnitude of the test results, the clinical history, and the results of other investigations. The interpretation of an abnormal amniotic fluid AFP test that is followed by a normal result of a careful ultrasound scan of the fetal back is that there is a 54.5% chance that the fetus has spina bifida if there is a previous history of spina bifida. There is a 12.5% chance if there is a negative family history. These calculations lead to informed genetic counseling and rational decision making with regard to the continuation of the pregnancy.
A family with a fragile site on chromosome 6 at band p23 was examined for recombination between the fragile site and HLA. Recombination was observed in four of the 20 offspring in whom it could occur. The estimate of the genetic length of chromosome between the fragile site and HLA is 20 centimorgans (cM) with a lower 95% probability limit of 8.5 cM, placing HLA proximal to the midpoint of 6p22. The most likely regional localization is at 6p21.3, which agrees closely with methods that do not involve recombination with the fragile site. This fragile site does not measurably disrupt recombination frequency, and the allele predisposing to expression of the fragile site is situated at the fragile site.
Amniotic fluid alpha-fetoprotein (AFP) assays and detailed ultrasound examinations were performed in 376 prenatal patients at risk for a neural tube defect (high-risk group). In addition, 2436 patients who underwent amniocentesis for other indications underwent preamniocentesis ultrasound screening and amniotic fluid AFP assays (low-risk group). There were 10 neural tube defects in the high-risk group (7 open and 3 closed) and 3 in the low-risk group (all open). Two of the 3 closed defects were detected prenatally. The predictive value of an elevated AFP level for an abnormal fetus was much higher in the high-risk (6 of 6, 100%) than in the low-risk group (1 of 6, 17%). When both ultrasound and AFP assay results were normal, the chance of a normal outcome was very high in both the high- and low-risk groups (99.7 and 100%, respectively). It was of particular interest that in the low-risk group, the likelihood of an abnormal outcome in women with elevated AFP and a normal ultrasonogram was low (0 of 5).
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A 12-year-old boy with recurrent skin ulceration, chronic generalized lymphedema, and mild mental retardation was found to excrete massive amounts of dipeptides, most (but not all) of which had proline or hydroxyproline as the carboxyl terminal residue. Glycylproline predominated. Prolidase deficiency was demonstrated in red blood cells and in fibroblastic cells. Prolidase activity was present in continuous lymphoid cell cultures at the same low level observed in control cells.
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