This topic has never been examined in the written paper, but an entire chapter of Oh's Manual is dedicated to it. It seemed important to include a summary of it in the Required Reading section.

Unless otherwise stated, the information below is derived from Oh's Manual.

For those without freegan access to The Manual or similar textbooks there really is no single resource to cover this topic. Satisfactory alternatives include the Google Books version of Stiehm's Immune Deficiencies (1156 pages!) and this 2009 update from the Journal of Allergy and Clinical Immunology. Unfortunately, for most people, the fastest revision strategy is to get Oh's Manual.

Immunodeficiency disorders can also be divided into primary and seocndary; primary being disorders where the immune system components are defective due to some sort of disabling mutation.

Defective neutrophils or neutropenia

Causes of Neutropenia or Neutrophil Dysfunction


Impaired neutrophil function

  • Decreased neutrophil production
    • Aplastic anaemia, MDS
    • Radiation poisoning
    • Nutrient deficiency (eg. B12)
    • Congential disorders
  • Increased neutrophil destruction
    • Haemodialysis or plasmapheresis
  • Sequestration
    • Hypersplenism
  • Drug-induced bone marrow suppression:
    • Arsenic
    • Chemotherapy
    • Clozapine
    • Chlorpromazine
    • Phenytoin
    • Chloramphenicol
  • Congenital defects
    • Chronic granulomatous disease (CGD)
    • Numerous rare disorders
  • Acquired defects
    • NIDDM
    • Vitamin C deficiency
    • Hypothermia
  • Immature neutrophils
    • GM-CSF
  • Drug-induced neutrophil dysfunction
    • Corticosteroids
    • Pantoprazole
    • Propofol
    • Thiopentone

Characteristic infections

These are mainly infections by extracellular pathogens:

  • Recurrent bacterial infections
  • Recurrent fungal infections (particularly abscesses in solid organs)
  • Oral and periodontal disease is common
  • They may have severe superinfected eczema
  • Wound healing is severely delayed
  • Systemic infections with catalase-positive organisms:
    • Staphylococcus aureus
    • Serratia
    • Aspergillus
    • Burkholderia cepacia
    • Nocardia

Laboratory investigations

  • Neutrophil count
  • Nitroblue tetrazolium reduction test (tests oxidative killing)
  • Neutrophil migration tests
  • Bacteria or Candida killing assay

Defective T- lymphocytes

Causes of T-Lymphocyte Deficiency or Dysfunction


Impaired T-cell function

  • Decreased production
    • Aplastic anaemia, MDS
    • Radiation poisoning
    • Nutrient deficiency (eg. B12)
    • Congential disorders
    • Di George syndrome
  • Increased destruction
    • Haemodialysis or plasmapheresis
    • HIV/AIDS
  • Sequestration
    • Hypersplenism
    • Recent viral infection
  • Drug-induced bone marrow suppression:
    • Chemotherapy
    • Corticosteroids
  • Congenital defects
    • Chronic mucocoutaneous candidiasis
    • APECED syndrome
    • Di George syndrome
  • Acquired defects
    • End-stage renal failure
    • Thymectomy
    • T-cell lymphoma
  • Immature lymphocytes
    • GM-CSF
  • Drug-induced lymphocyte dysfunction
    • Essentially any drugs used to prevent solid organ rejection


Characteristic infections

These are mainly infections by intracellular pathogens and colonising opportunists

  • Recurrent viral diseases:
    • HSV, VZV, EBV, CMV
  • Recurrent bacterial diseases:
    • Listeria
    • Salmonella
    • Shigella
  • Fungal infections:
    • Candida
    • Cryptococcus
    • Aspergillus
  • Protozoal infections:
    • Toxoplasma
    • Pneumocystis

Laboratory investigations

  • T-cell subset count (CD4, CD8 counts)
  • Cytokine assays
  • Delayed-type hypersensitivity (DTH) skin test responses to antigens

Defective antibodies

Causes of Failre in Humoural Immunity

Decreased antibody production

Defects of antibody function

  • Congenital:
    • X-linked agammaglobulinaemia
    • hyper-IgM immunodeficiency syndrome
    • Common variable immunodeficiency (CVID)
  • Acquired:
    • B-cell leukaemia
    • Aplastic anaemia, MDS
    • Radiation poisoning
    • Asplenia
    • Phenytoin
  • Congenital defects
    • Rare isotype or light chain deficiencies
  • Acquired defects
    • NIDDM (impaired Fc fragment function)
  • Drug-induced immunoglobulin synthesis failure
    • Corticosteroids


Characteristic infections

  • Recurrent bacterial infection, particularly by encapsulated organisms:
    • Streptococcus pneumoniae
    • Neisseria meningitides
    • Haemophilus influenzae

Laboratory investigations

  • Peripheral B-cell count
  • IgG subclasses (serum levels)
  • Assessment of antibody response to immunization, eg. polysaccharide antigens and protein antigens.

Defective complement

Causes of Complement Deficiency

Congential complement deficiency

Acquired complement deficiency

  • Congenital deficiency of C3 ( severe recurrent pyogenic infections)
  • Deficiency of MAC components is more common (recurrent meningococcal infections)
  • Deficiency of classical pathway components (C1, C2, C4) (recurrent meningococcal infections)
  • Plasmapheresis
  • Haemodialysis
  • Persistent bacterial infections, causing depletion
  • Cirrhosis
  • SLE
  • Overwhelming sepsis

Characteristic infections

Generally speaking, bacterial infections dominate the spectrum:

  • Streptococcus pneumoniae
  • Neisseria meningitides
  • Moraxella
  • Acinetobacter

Laboratory investigations

  • Complement levels
  • Functional assay of the classical pathway (CH50)
  • Functional assay of the alternative pathway

Post-splenectomy state

The post-splenectomy state is another form of immunodeficiency, and clinically it looks a lot like a failure of humoural immunity. This has come up in the exams a lot, and therefore merits its own summary page.


Oh's Manual: Chapter 67 (pp. 703)  Host  defence  mechanisms  and  immunodeficiency  disorders by Steven  McGloughlin  and  Alexander  A  Padiglione

Marhoffer, Wilhelm, et al. "Impairment of polymorphonuclear leukocyte function and metabolic control of diabetes." Diabetes care 15.2 (1992): 256-260.

Notarangelo, Luigi D., et al. "Primary immunodeficiencies: 2009 update."Journal of Allergy and Clinical Immunology 124.6 (2009): 1161-1178.