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10 Cards in this Set
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C2. Guanine nucleotide binding proteins play regulatory role in many signal transduction pathways within the cell. Abnormalities of guanine nucleotide binding protein have been associated with several clinical disorders. Which of the following disorders results from inactivating mutations of the guanine nucleotide binding protein Gs?
A. Albright hereditary osteodystrophy B. insulin unresponsiveness C. McCune-Albright syndrome D. nephrogenic diabetes insipidus E. type II diabetes mellitus |
Answer: A. Mutations causing deficiency of G proteins occur in Albright osteodystrophy while activating mutations in the same gene cause McCune-Albright.
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C3. An infant dies at ten days of age, and autopsy reveals clinical features that include: agyria, cerebellar hypoplasia, Dandy-Walker cyst, microphthalmia, and retinal detachment with retinal dysplasia. Which of the following syndromes if the most likely diagnosis?
A. Meckel-Gruber syndrome B. Miller-Dieker syndrome C. Neu-Laxova syndrome D. Pallister-Hall syndrome E. Warburg syndrome |
Answer: E. This is a typical description for a patient with Warburg syndrome. A patient wlth Meckel-Gruber syndrome would more likely have encephalocele, polydactyly, and polycystic kidney disease. The Pallister-Hall syndrome is characterized by hypothalamic hamartoblastoma, hypopitutarism, imperforate anus, and postaxial polydactyly. The Neu-Laxova syndrome is characterized by microcephaly or lisssencephaly, elfin-facies with exophthalmos, and syndactyly with subcutaneous edema. The Miller-Dieker syndrome is characterized by lissencephaly.
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C4. Prader-Willi is a genetic syndrome characterized by failure to thrive during the first year of life, developmental delay in most patients, small hands and feet (more noticeable in late childhood), crytorchidism in males, a facial gestalt that is recognizable in many patients and food- seeking behaviour after age two. Even so clinical diagnosis can be difficult because of the variability in the phenotype and laboratory studies have become the mainstay of diagnosis. Which of the following laboratory analyses is most likely to reveal a positive finding in a young child where the constellation of clinical features above is not readily identifiable?
A. FISH analysis for missing SNRPN locus B. High-resolution chromosome analysis C. Imprinting assessment with DNA methylation assay D. Routine chromosome analysis and karyotype E. Subtelomeric probe analysis by FISH studies |
Answer C. Consensus clinical diagnostic criteria are accurate, but the mainstay of diagnosis is DNA-based methylation testing to detect abnormal parent-specific imprinting within the Prader-Willi critical region (PWCR) on chromosome 15, this testing determines whether the region is maternally inherited only (i.e., the paternally contributed region is absent) and detects more than 99% of affected individuals. Methylation-specific testing is important to confirm the diagnosis of PWS in all individuals, but especially those who have atypical findings or are too young to manifest sufficient features to make the diagnosis on clinical grounds.
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C1. A concerned mother brings her 18-month-old daughter to the pediatrician's office because she has been intermittently constipated. Her mother became alarmed while changing her diaper straining to have a stool, she found some red, tissue bulging from the rectum. Which of the following procedures or laboratory studies is most like to identify the appropriate diagnosis?
A. Colonoscopy for Crohn disease. B. Molecular analysis for Duchenne muscular dystrophy C. Rectal biopsy Hirschsprung disease D. Renal ultrasound for Beckwith-Wiedemann syndrome |
Answer: E. Rectal prolapse is a frequent feature of CF and should raise concern about that diagnosis.
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C5. A newborn infant has the Robin sequence. The mother was diagnosed with arthritis in childhood and has had a retinal detachment. Which of the following is the most likely syndromic diagnosis?
Acromesomelic dysplasia Rieger syndrome Stickler syndrome Treacher Collins syndrome Warburg syndrome |
Answer: C. This would be a reasonably good story for Stickler syndrome. The arthropathy can simulate juvenile rheumatoid arthritis. Retinal detachment is a feature. Robin sequence can occur in childhood. The other disorders would all be quite different.
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C6. Radial ray anomalies distinguished by the presence or absence of thumbs can provide a clue
toward an appropriate diagnosis. In which of the following syndromes are thumbs consistently present? Thrombocytopenia and absent radius syndrome Fanconi anemia Holt-Oram syndrome VATER association de Lange syndrome |
Answer: A. The thumbs may be absent in any of these disorders except TAR where they are consistently present.
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C7. Soft cystic masses in the auricle which develop into hypertrophic cartilage are a typical feature of which of the following skeletal dysplasias?
Achondroplasia Camptomelic dysplasia Chondroectrodermal dysplasia Diastrophic dwarfism Larsen syndrome |
Answer: D. This description of the changes in the ear is typical of diastrophic dwarfism. It is a very distinctive change but is usually not present in the neonatal period.
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C8. A 28-year-old woman underwent amniocentesis for chromosomal analysis when her fetus was
found to have limbs that were short for the assigned dates. The karyotype was 46,XY. At birth the baby had female appearing genitalia. These clinical findings are most consistent with which of the following syndromes? Achondrogenesis type IA Achondrogenesis type II Campomelic dysplasia Jeune thoracic dystrophy Thanatophoric dysplasia |
Answer: C. Female appearing genitalia in an XY infant is a common feature of campomelic dysplasia, but is not a feature of the other disorders.
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C9. A 1-year-old boy presents with an episode of fever on a 90 degree day in July and there is no evidence of an infection. His parents note that he never seems to sweat in the extreme heat of the summer. He has extremely sparse hair. Skull x-rays show absence of most of the primary tooth buds. Which of the following statements reflects the most likely inheritance pattern for this disorder?
A. He likely has an autosomal dominant disorder. B. He likely has an autosomal recessive disorder. C. He likely has a sporadically occurring disorder. D. He likely has an X-linked dominant disorder. E. He likely has an X-linked recessive disorder |
Answer: E. This clinical description is very suggestive of anhidrotic ectodermal dysplasia, which is usually X-linked. Many other forms with different inheritance occur. This story is typical for the X-linked disorder but is not diagnostic of that pattern of inheritance.
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C10. A newborn infant has extreme hypotelorism, microcephaly, midline cleft, poor temperature regulation, seizures, and no anomalies below the neck. Which of the following syndromes is best described by these findings? A. Ellis van Creveld syndrome B. Holoprosencephaly C. Meckel-Gruber syndrome D. Trisomy 13 E. Trisomy 18
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Answer: B. This is a typical description of holoprosencephaly. The trisomies and Meckel-Gruber syndrome would likely be associated with additional features below the neck. The CNS abnormalities would not be a feature of Ellis van Creveld although cardiac defect and limb abnormalities would be present.
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