Immunoglobulin deficiency OSCE

Clinical Immunology
by Medical Educator Clinical Immunology

An immunoglobulin (Ig) deficiency refers to a condition where an individual has low levels of immunoglobulins or antibodies in their blood. Antibodies are proteins produced by the immune system to fight off infections and diseases. An Ig deficiency can increase an individual’s susceptibility to infections and other immune-related disorders.

There are several types of Ig deficiencies, ranging from mild to severe, and they can be caused by a variety of factors, including genetic predisposition, autoimmune diseases, and certain infections. Treatment for Ig deficiency typically involves administration of immunoglobulin therapy to help boost the individual’s immune system and protect against infections.

Our patient station below focusses on a patient with recurrent streptococcus pneumonia. Recurrent Streptococcus pneumoniae infections refer to repeated episodes of pneumonia caused by the Streptococcus pneumoniae bacteria. Recurrent infections can be a result of several factors, including weakened immune system, chronic health conditions, and exposure to contaminated environments. Test your understanding in this patient-focussed OSCE example.

Table of Contents

Question 1

A patient with no other comorbidities presents with recurrent streptococcus pneumonia. He has no other medical problems, but at 32 has been admitted to intensive care with pneumonia on one occasion.

In between the events he is well. His IgG, IgA, and IgM levels have previously been checked and are normal.

He recovers well: what is the next most appropriate step?

  • Check functional antibodies
  • HRCT thorax
  • Full Pulmonary function tests
  • Lung biopsy
  • Bronchoscopy

Check functional antibodies

Functional antibodies will give you the Ig subclasses which are potentially deficient.

A selective deficiency of an Ig subclass sounds like the most likely diagnosis here: note the pneumonia is always a certain microbial subtype.

Although you may consider any of teh other tests (apart from the lung biopsy) as part of baseline investigations, the functional antibodies are the best answer.

Antibody titres measured from this will include haemophilus, tetanus and pneumococcus.

Question 2

Continued from previous question.

Assuming he has a functional deficiency to strep. pneumonia, which immunoglobulin would be most likely to be responsible for the increased susceptibility?

  • IgG
  • IgM
  • IgA
  • IgE
  • Bronchoscopy

IgG

The immune system is adapting properly to antigen presentation\: i.e. the patient has had recurrant exposures but is not mounting a response. Therefore its most likely that the IgG subclass will be deficient.

Question 3

Continued from previous question.

Assuming he has a functional deficiency to strep. pneumonia: which cell is responsible for making the immunoglobulin?

  • Natural Killer Cell
  • Antigen Presenting cell
  • Neutrophil
  • T Cell
  • B cell

B cell

B-cells differentiate into plasma cells which in turn secrete immunoglobulin.

Question 4

Continued from previous question.

A patient with no other comorbidities presents with recurrent streptococcus pneumonia. He has no other medical problems, but at 32 has been admitted to intensive care with pneumonia on one occasion.

In between the events he is well. His IgG, IgA, and IgM levels have previously been checked and are normal.

He presents two months later with a red swollen knee and a fever. His blood tests show an elevated CRP (213 NR<5) and an elevated serum urate (418 NR 200-400).

He is not able to weight bear on his knee.

He also has some persistent right upper quadrant pain.

O/E
T378
BP 112/90
P102
CVS\: normal heart sounds
RESP\: some reduced air entry at the right base on auscultation although there are no crackles in the chest. Percussion not is slightly dull at the right base.
GIT\: NAD
Musculoskeletal system\: Swollen right knee with effusion.

What is the most likely cause of his knee pain?

  • Septic Arthritis
  • Gout
  • Systemic lupus erythematosus
  • Reactive arthritis
  • Seronegative arthritis

Septic Arthritis

In any acute monoarthritis you need to have septic arthritis as a consideration as this is the most important diagnosis not to “miss” in an exam.

IN this case thee urate is slightly elevated but:

  • he has no history of gout
  • urate is a very non specific marker
  • he has a more likely predisposition to one of the other problems i.e. he has an immunodeficiency

Therefore the “best” answer is septic although it could be any of the other answers.

Question 5

Continued from previous question.

Assuming his knee is aspirated and sent for microscopy culture and sensitivity, what is the most likely finding?

  • Gram positive rod
  • Gram positive cocci
  • Gram negative rod
  • Gram negative cocci
  • Negatively birefringent crystals

Gram positive cocci

Question 6

Continued from previous question.

What is the most likely cause of his right upper quadrant pain?

  • Pleuritic chest pain
  • Liver abscess
  • Appendicitis
  • Cholecystitis
  • Cholangitis

Pleuritic chest pain

He has recurrent pneumococcus (strep pneumonia) infection: He is likely to have pneumococci in his knee but where did they come from?

Most likely his chest.

Does this fit in with the findings? YES!

Right basal chest signs, and an otherwise normal examination.

Remember cholangitis is differentiated from cholecystitis by the prominance of fever/rigors and jaundice (although you can be jaundiced with cholecystitis.

Question 7

Continued from previous question:

Assuming he has a septic arthritis and systemic pneumococci infection, what other treatment other than antibiotics is likely to be beneficial?

  • IV immunoglobulin
  • Plasma Exchange
  • IV methylprednisolone
  • Granulocyte Colony Stimulating Factor (G-CSF)
  • IV Chlorphenamine

IV immunoglobulin

He has recurrent pneumococcus (strep pneumonia) infection: He is not making IGM immunoglobulin correctly. As a result of this his adaptive immune system is not responging effectively. IVIg is pooled immunoglobulins from a number of patients which is given intravenously to supplement his own immunoglobulin production.