SCID : Definition, Causes, Symptoms, Treatment And MCQs for NEET, GPAT, CSIR NET JRF, UPSC, SSC Exam

SCID : Definition, Causes, Symptoms, Treatment And MCQs for NEET, GPAT, CSIR NET JRF, UPSC, SSC Exam

” SCID (Severe combined immunodeficiency) is basically caused due to the deficiency of an enzyme called adenosine deaminase enzyme. In this group of immunodeficiency disease, there is a B – cell and T – cell defect which are its characteristic feature.”

1.] SCID stands for Severe Immunodeficiency Disease.


SCID is caused due to some defects in the gene. Depending on the location of the mutant gene and the nature of the genetic defect, two pattern of inheritance are seen : autosomal recessive and X – linked recessive. In the autosomal recessive form of SCID, approximately 40% of the patients lack the enzyme adenosine deaminase, due to which there is an accumulation of deoxyadenosine and its derivatives, which is toxic to immature lymphocyte, which leads to the markable reduction of T – lymphocytes in person’s body.


Following are the signs and symptoms of SCID :-

  • During the growth of the child, child doesn’t gain weight i.e; there is retarded growth.
  • There is a chronic diarrhea.
  • Frequent infection due to lack of T – lymphocyte.
  • Serious respiratory infections.
  • Skin rashes, pneumonia, meningitis.
  • Also affected infants are susceptible to recurrent, severe infection by a wide range of pathogens including Pseudomonas, Varicella, Candida albicans etc.


Currently, bone marrow transplantation is the mainstay of treatment, but with the elucidation of genetic defects, specific gene therapy is on the horizon.

SCID Gene Therapy

The above image is taken for education purpose only from



1.] All of the following are immunodeficiency disease except ?

a. Grave’s disease


c. Di George’s syndrome

d. Hyper IgM syndrome

2.] All of the following are autoimmune disorder except ?

a. Grave’s disease


c. Rheumatoid arthritis

d. Addison’s disease

3.] SCID can occur due to the absence of an enzyme ?

a. Adenosine deaminase

b. Guanosine deaminase

c. Phosphorylase

d. Thymidine deaminase

4.] In SCID, the patients are deficient in ?

a. B cells

b. T cells

c. Both (a) and (b)

d. IgA

5.] Immune disorders include ?

a. Hypersensitivity

b. Auto – immune disease

c. Immunodeficiency

d. All of the above

6.] The major chemical messenger involved in hypersensitivity is ?

a. Interleukin

b. Lymphokines

c. Histamines

d. Interferon

7.] Which of the following Ig is involved in mediated allergic reactions ?

a. IgG

b. IgM

c. IgE

d. IgA

8.] Majority of auto immune disease are ?

a. Cell mediated

b. Antibody mediated

c. Macrophage mediated

d. Mast cell mediated

9.] SCID primarily affects ?

a. Macrophages, mast cell and T cells

b. T cell only

c. T cells and dendritic cell

d. T cell, B cell and in some case NK cell

10.] SCID meant ?

a. Severe Combined Immunodeficiency

b. Severe Combined Immunoefficiency

c. Sudden Combined Immunodeficiency

d. None of the above is correct



1.] (a) Grave’s disease

2.] (b) SCID

3.] (a) Adenosine deaminase

4.] (c)

5.] (d)

6.] (c) Histamine

7.] (c) IgE

8.] (b) Antibody mediated

9.] (d) T cell, B cell and in some case NK cell

10.] (a) Severe Combined Immunodeficiency


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1.] Robbin’s Basic Pathology; 5th edition; Page no. 218.

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