A 54-year-old woman is treated with rituximab for non-Hodgkin's lymphoma.
What is the target of rituximab?
Correct Answer A: Rituximab - monoclonal antibody against CD20.
Monoclonal antibodies:
Monoclonal antibodies have an increasing role in medicine. They are manufactured by a technique called somatic cell hybridization. This involves the fusion of myeloma cells with spleen cells from a mouse that has been immunized with the desired antigen. The resulting fused cells are termed a hybridoma and act as a 'factory' for producing monoclonal antibodies. The main limitation to this is that mouse antibodies are immunogenic leading to the formation of human anti-mouse antibodies (HAMAs). This problem is overcome by combining the variable region from the mouse body with the constant region from an human antibody.
Clinical examples of monoclonal antibodies:
Monoclonal antibodies are also used for:
A 25-year-old man who has been morbidly obese for the past five years is reviewed in the endocrinology clinic.
In this patient, which one of the following hormones would increase appetite as levels increase?
Correct Answer D:
Obesity hormones:
Whilst thyroxine can increase appetite it does not fit with the clinical picture being described.
Obesity: physiology:
1- Leptin: Leptin is thought to play a key role in the regulation of body weight. It is produced by adipose tissue and acts on satiety centres in the hypothalamus and decreases appetite. More adipose tissue (e.g. in obesity) results in high leptin levels.
Leptin stimulates the release of melanocyte-stimulating hormone (MSH) and corticotrophin-releasing hormone (CRH). Low levels of leptin stimulates the release of neuropeptide Y (NPY).
2- Ghrelin: Where as leptin induces satiety, ghrelin stimulates hunger. It is produced mainly by the fundus of the stomach and the pancreas. Ghrelin levels increase before meals and decrease after meals.
A 50-year-old man is reviewed in the neurology clinic. For the past four months he has been experiencing problems with his right shoulder. On examination he has weakness of shoulder abduction and to a lesser extent weak elbow flexion. A small patch of numbness is noted over the deltoid muscle but otherwise sensation is normal.
Where is the neurological lesion?
Correct Answer B: This man has weakness of both the deltoid (C5, C6) and the biceps muscle (C5, C6, C7). The location of the sensory loss points to a C5 lesion however.
Upper limb anatomy: The information below contains selected facts which commonly appear in examinations:
Deltoid muscle:
Which one of the following is in direct anatomical contact with the left kidney?
Renal anatomy: The tables below show the anatomical relations of the kidneys:
Right kidney:
Left kidney:
Which one of the following statements regarding relative risk is correct?
Correct Answer B: Remember that risk and odds are different. If 20 patients die out of every 100 who have a myocardial infarction then the risk of dying is 20 / 100 = 0.2 whereas the odds are 20 / 80 = 0.25.
Relative risk: Relative risk (RR) is the ratio of risk in the experimental group (experimental event rate, EER) to risk in the control group (control event rate, CER). The term relative risk ratio is sometimes used instead of relative risk.
To recap:
For example, if we look at a trial comparing the use of paracetamol for dysmenorrhoea compared to placebo we may get the following results: Total number of patients Experienced significant pain relief:
If the risk ratio is > 1 then the rate of an event (in this case experiencing significant pain relief) is increased compared to controls. It is therefore appropriate to calculate the relative risk increase if necessary (see below).
If the risk ratio is < 1 then the rate of an event is decreased compared to controls. The relative risk reduction should therefore be calculated (see below).
Relative risk reduction (RRR) or relative risk increase (RRI) is calculated by dividing the absolute risk change by the control event rate.
Using the above data, RRI = (EER - CER) / CER = (0.6 - 0.25) / 0.25 = 1.4 = 140%
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