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Quiz:Infectious Diseases

From Mediwikis

1. A 54 year old businessman who returned from a holiday in India 10 days ago presents at his GP, complaining that his skin has turned yellow. He has been suffering from abdominal pain, fatigue and nausea for the past week and has just developed a fever.

What is your differential diagnosis? Why?

Hepatitis A

How would you test for this?
  • Faecal test – Hep A virus is excreted in the faeces towards the end of the incubation period
  • IgM antibodies – detectable 1-2 weeks after infection
  • IgG antibodies – acute illness has passed and the patient now has long-term immunity to further infection

2. 35 year old Geordie man attends a sexual health clinic, complaining of dark urine. It is noted that he is jaundiced and has a fever. He has just returned from one year in Thailand, and jovially reported having sex with ‘many women’. He states he has never used illegal drugs and has not received any blood transfusions in the past ten years.

What is your differential diagnosis?

Hepatitis B

How would you diagnose this?

Most diagnostic tests looks for HBsAg and the total anti HBc You can remain positive for HBsAg for over 6 months after initial infection, if this is the case then you are thought to be in a ‘carrier’ state. Carriers who are HBeAg negative have low viral activity, so there is a low chance of transmission and long term complications

What are the long term complications of this condition?

Complications include chronic hepatitis B (10%), hepatocellular carcinoma and liver failure (1%)

3. A 73 year old woman with COPD is admitted to hospital with an acute history of shortness of breath, cough and fever. She is bringing up green mucus, but no blood. She is a smoker (30 pack years) and has had numerous similar admissions in the past few years.

What is your differential diagnosis?

Pneumonia

What signs would be worrying at this point?

High CURB-65 score(see Pneumonia)

What kind of organisms could cause this?

Streptococcus pneumoniae, mycoplasma pneumoniae, Legionella pneumophilia, Chlamydia psittaci

4. A 19 year old medical student is found collapsed on her floor by her flatmates. She appears generally unwell, with a fever, headache and stiff neck. She seems intolerant to bright light and is irritable. On examination she has a non-blanching rash on her abdomen.

What is your diagnosis?

Mengococal septicaemia (not just Meningitis)

What organisms could cause this condition in this patient?

Nisseria meningitidis, Streptococcus pneumoniae

How would you manage this patient?
  • ABCDE management first
  • Third generation cephalosporin/ benzylpenicillin ASAP
  • Lumbar Puncture- gram +ve polymorphs, high White Cell Count
  • Cultures for tailoring treatment later

5. A 45 year old man presents to clinic with a two week history of a flu-like illness that has recurred many times in the last 10 years. On examination you notice that he has a white coating on his tongue and a number of reddish-brown raised rashes on his upper back. He has just moved to the UK and has lived his life in rural sub-Saharan Africa. Situation

What is your diagnosis?

AIDS

What is the pathogenesis of this condition?

The virus targets CD4 T lymphocytes:

  1. Binding- To CD4 receptors, via the glycoprotein gp 120, and coreceptors CCR5 and CXCR4.
  2. Fusion- between gp 41 and the cell membrane
  3. Reverse Transcription- RNA is uncoated, DNA copies are made, and dsDNA is formed by DNA Polymerase.
  4. Integration- This viral DNA is integrated into the host's genome
  5. Transcription & Translation- DNA is replicated to form Viral RNA, and Viral mRNA, which forms structural proteins.
  6. Budding- the virus is assembled from the RNA and proteins, and released from the host cell.

6. A 22 year old medical student returns from her elective in Tanzania with a three day history of alternating fever and chills. She has an intense headache, fatigue and appears generally very unwell. She missed her vaccination appointment before her elective and therefore did not take any prophylaxis for infectious diseases during her stay. Situation

What is your differential diagnosis?

Malaria Situation

Describe the life cycle of this parasite

The Plasmodium parasite is transmitted only by the female Anopheles mosquito (males feed on plant nectar).When the mosquito bites a human, the sporozoites travel to the liver and reproduce asexually in hepatocytes to produce thousands of merozoites. These merozoites infect red blood cells, and further multiply, into both more merozoites, and gametocytes. The gametocytes are taken up into the mosquito gut along with the blood of the mosquitos meal, where they fuse to form sporozoites.

What are the pharmacological management options?

Quinine, Chloroquine, Malarone, Artemisinin

Point added for a correct answer:  
Points for a wrong answer:
Ignore the questions' coefficients:

1. Select the most likely causative organism for each situation

  • A Streptococcus pneumoniae
  • B Staphylococcus aureus
  • C Mycoplasma pneumoniae
  • D Legionella
  • E Klebsiella pneumonia
  • F Mycobacterium tuberculosis
A B C D E F
1. 65 year old woman with a two day history of dyspnoea, cough producing green phlegm.
2. 24 year old smoker returns from a 12 week holiday in west africa with a dry cough and feeling feverish at night
3. Age 56 homeless alcoholic with chest pain and progressive shortness of breath. X ray reveals a cavitating lesion in the right upper lobe.

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