Immunodeficiency Types: Primary & Secondary, Diagnosis, Treatment

Immunodeficiency disorders are conditions that prevent the body from fighting back infections and diseases. As a result, it becomes extremely easy for the patient to catch viruses and bacterial infections because of the lack of immune response from the body. 

Immunodeficiency disorders are an essential topic in Pathology. Read this topic thoroughly to understand everythig you need to know about immunodeficiency disorders and elevate your NEET PG preparation. 

Types of immunodeficiency

• Primary immunodeficiency
• Secondary immunodeficiency

Secondary immunodeficiency

• Causes
  • Malnutrition (most common)
  • HIV/ Aids
  • Cancer
  • Chemotherapy

Primary immunodeficiency

It is divided into 3 groups

1. Defect in Lymphocytes maturation 
2. Defect in lymphocytic activation and function
3. Systemic disease

Defect in Lymphocytes maturation

1. SCID
2. Bruton's hypogammaglobulinemia
3. Bare lymphocyte syndrome
4. Digeorge syndrome

1. SCID ( Severe Combined Immunodeficiency)

• B, T, NK cells are affected. 
• It is of two types

XLR ( X linked recessive variety)

• Most common problem in the gamma subunit of cytokine receptors: IL2, IL4, IL7, IL15). 
• NK cell defect is there because IL 2 and IL15 will not function properly. 
• B cells are good, but T cells are not there because for T cells IL 7 is required and IL 7 is not there so T cells will not be there.
• The antibody will not be produced because IL 4 is not there.

AR ( Autosomal recessive variety)

• ADA ( Adenosine deaminase) deficiency(most common)
• Involves all cells (B, T, NK)
• JAK3 defect: Affects cytokine development. (T, NK cells are gone, B cells are there)
• RAG1 and RAG2 (Recombinant activation gene) defect: Needed to develop B, T cell receptor. NK will be there. 
• If all the B, T, and NK cells are defective, then it will be ADA deficiency that is autosomal recessive.
• If B and T cells are defective and NK cells escape, it will be RAG 1,2. 
• If T and NK cells are defective and B cells are there, it can be XLR and AR. 

Clinical features

• Morbilliform rash 
  • Red rash on face of child
  • Maternal T cells attack featal skin
• Pneumonia
• Pneumocystis
• CMV

Treatment

First disease to be treated with gene therapy

• For Gamma subunit (XLR) 
• T cell proliferation started (Leukemia)

Enzyme replacement used now 

• ADA deficiency

2. Bruton's hypogammaglobulinemia

• Occurs most commonly in boys, XLR
• BTK gene defect
• B cell defect 

              Bruton tyrosine kinase

Immature B cells  ------ mature B cells   -------  plasma cells and antibodies 

• BTK is not there, so B cells won't mature, then plasma cells and antibodies will not be formed.
•  Less antibodies will cause hypogammaglobulinemia. 

Clinical features

• Enterovirus infections
• Polio
• ECHO
• Coxsackie virus infection. 
• Live polio vaccine is always contraindicated. 
• Reduced IgG → defective optimisation 

3. Bare lymphocyte syndrome

• MHC II is missing

4. Digeorge syndrome

• Also known as Velo Cardio Facial syndrome. There is deletion 22q11 (TBX 1 gene is going to be deleted) → 3rd and 4th pharyngeal pouches are not developed. Thymus and parathyroid hormones will not form.  Reduced parathyroid hormones, reduced calcium levels → hypocalcaemia. T cells mature in Thymus, if thymus won't mature and cause thymic aplasia and  T cell defect will be there.  Also known as velo cardio facial syndrome.
• Tetralogy of fallot. 
• Abnormal facies are there: Cleft in lip and cleft palate. 

Diagnosis

• FISH: diagnosis of choice
• TBXgene:  seen in digeorge syndrome and schizophrenia.

Defect in lymphocytic activation and function

1. Common variable Immunodeficiency (CVID)
   • It is a B and T cell problem. B cell problem is because of the BAFF gene defect and the T cell problem is because of ICOS gene defect. 

Differences between Bruton's hypogammaglobulinemia and CVID. 

• The BTK gene converts immature B cells into mature B cells. The Baff gene then makes plasma cells and antibodies from mature b cells. 

Bruton's hypogammaglobulinemia	CVID
BTK gene defectOccurs in boysB cell defectHypoplastic germinal centers	BAFF gene defectOccurs in boys & girlsB & T Cell defectHypergerminal centers

2. Hyper IgM syndrome
   • B cells have CD40 receptors and T cells have CD40 ligand. B cells have 2 antibodies: IgD and IgM. Ag comes, it will be given from B cell to T cells.  The T cell will be making IL 4. Then it will form GAMDE from MD. If there is a CD40 receptor or CD40 ligand defect, then this process won't occur. MD will not change in GAMDE there will be hyper IgM syndrome. CD40L also known as CD 154. The patients of hyper IgM syndrome are at the risk of pneumocystis carinii.
3. Hyper IgE Syndrome
   • Mutation: STAT 3 defect It is also known as job's disease.
4. Isolated IgA Syndrome
   • IgA is a mucosal antibody present in mucosa (GIT, respiratory mucosa). when IgA goes down, mucosal immunity goes down that causes mucosal infection. GIT affected diarrhoea. Respiratory mucosa affected respiratory infections. In the patients of Isolated IgA deficiency, washed RBCs are given to patients. 
5. XLP disorder ( X linked lymphoproliferative syndrome)
   • SAP defect (SLAM activating protein)
   • SLAM: Signal Lymphocyte Activation Molecule
   • Needed by B/T/NK cells
   • Increased risk of EBV infections

Systemic disease

1. Wiskott Aldrich Syndrome (WAS)
   • X linked recessive disorder, chromosome X and WASP gene defect. Patients have bleeding manifestations (because of platelet defects, small size platelets)
   • Infections
   • eczema.
   • Ig profile: IgM goes down, IgA and IgE goes up
2. Ataxia Telangiectasia
   • Dilated blood vessels are there.
   • It is associated with ATM gene
   • Immunodeficiency is also there. 

Q. A new born child presents with a morbilliform rash. Mother also gives a history of recurrent diaper rash. Examination reveals oral candidiasis and failure to thrive?

A. LAD 1
B. LAD 3
C. Bruton's agammaglobulinemia
D. SCID

Q. BAFF genetic defect associated with germinal centre hyperplasia leading to hyperplasia of peyer's patches and tonsils? 

A. Bruton's agammaglobulinemia
B. SCID 
C. CVID 
D. CGD

Q. Select the incorrect match?

A. Del 22p - DiGeorge syndrome 
B. Baff - CVID
C. ADA deficiency - SCID 
D. BTK - Bruton's hypogammaglobulinemia. 

And that is everything you need to know about Immunodeficiency disorders for your Pathology preparation. For more informative and interesting blog posts like this, download the PrepLadder App and keep following our blog!