A 34-year-old man is reviewed in clinic. He has recently had his annual echocardiogram showing no change in the dilation of his aortic sinuses or mitral valve prolapse. You note he is tall with pectus excavatum and arachnodactyly.
His condition is primarily due to a defect in which one of the following proteins?
Correct Answer B:
Although fibrillin is the primary protein affected (due to a defect in the fibrillin-1 gene) it should be noted that fibrillin is used as a substrate of elastin.
Marfan's syndrome:
Marfan's syndrome is an autosomal dominant connective tissue disorder. It is caused by a defect in the fibrillin-1 gene on chromosome 15 and affects around 1 in 3,000 people.
Features:
The life expectancy of patients used to be around 40-50 years. With the advent of regular echocardiography monitoring and beta-blocker/ACE-inhibitor therapy this has improved significantly over recent years. Aortic dissection and other cardiovascular problems remain the leading cause of death however.
Which one of the following causes of hyponatraemia is least associated with a urinary sodium > 20 mmol/L?
Correct Answer C:
Hyponatraemia:
Hyponatraemia may be caused by water excess or sodium depletion. Causes of pseudo-hyponatraemia include hyperlipidaemia (increase in serum volume) or a taking blood from a drip arm. Urinary sodium and osmolarity levels aid making a diagnosis.
1- Urinary sodium > 20 mmol/l:
a- Sodium depletion, renal loss (patient often hypovolaemic):
b- Patient often euvolaemic:
2- Urinary sodium < 20 mmol/l:
a- Sodium depletion, extra-renal loss:
b- Water excess (patient often hypervolaemic and oedematous):
Which of the following is least recognised as a cause of macroglossia?
Macroglossia Causes:
Patients with Down's syndrome are now thought to have apparent macroglossia due to a combination of mid-face hypoplasia and hypotonia.
Which one of the following cell organelles contains double-stranded circular DNA?
Correct Answer E:
Cell organelles:
The table below summarizes the main functions of the major cell organelles:
A 31-year-old woman is diagnosed with familial hypercholesterolaemia. Genetic testing shows that she is heterozygous for the condition. You discuss the possibility of screening her relatives.
What is the chance her brother will also be affected?
Correct Answer A:
As familial hypercholesterolaemia is an autosomal dominant condition 50% of the first-degree relatives of heterozygotes will be affected.
Familial hypercholesterolaemia: Familial hypercholesterolaemia (FH) is an autosomal dominant condition that is thought to affect around 1 in 500 people. It results in high levels of LDL-cholesterol which, if untreated, may cause early cardiovascular disease (CVD). FH is caused by mutations in the gene which encodes the LDL receptor protein.
Clinical diagnosis is now based on the Simon Broome criteria:
Management:
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