Severe combined immunodeficiency




Severe combined immunodeficiency

Immune system

General infections


Neonatal sepsis


Hypersensitivity reactions

Type I hypersensitivity

Food allergy



Type II hypersensitivity

Immune thrombocytopenic purpura

Autoimmune hemolytic anemia

Hemolytic disease of the newborn

Goodpasture syndrome

Rheumatic heart disease

Myasthenia gravis

Graves disease

Pemphigus vulgaris

Type III hypersensitivity

Serum sickness

Systemic lupus erythematosus

Poststreptococcal glomerulonephritis

Type IV hypersensitivity

Graft-versus-host disease

Contact dermatitis


Transplant rejection

Graft-versus-host disease

Cytomegalovirus infection after transplant (NORD)

Post-transplant lymphoproliferative disorders (NORD)


X-linked agammaglobulinemia

Selective immunoglobulin A deficiency

Common variable immunodeficiency

IgG subclass deficiency

Hyperimmunoglobulin E syndrome

Isolated primary immunoglobulin M deficiency

Thymic aplasia

DiGeorge syndrome

Severe combined immunodeficiency

Adenosine deaminase deficiency


Hyper IgM syndrome

Wiskott-Aldrich syndrome

Leukocyte adhesion deficiency

Chediak-Higashi syndrome

Chronic granulomatous disease

Complement deficiency

Hereditary angioedema


Immune system organ disorders


Ruptured spleen

Immune system pathology review

Blood transfusion reactions and transplant rejection: Pathology review

Immunodeficiencies: T-cell and B-cell disorders: Pathology review

Immunodeficiencies: Combined T-cell and B-cell disorders: Pathology review

Immunodeficiencies: Phagocyte and complement dysfunction: Pathology review


Severe combined immunodeficiency


0 / 11 complete

USMLE® Step 1 questions

0 / 2 complete

High Yield Notes

3 pages


Severe combined immunodeficiency

of complete


USMLE® Step 1 style questions USMLE

of complete

An 18-month-old boy is brought to the emergency department for evaluation of shortness of breath and cough. Past medical history includes two episodes of pneumonia, oral thrush, chronic diarrhea and recurrent otitis media. His vaccinations are not up to date due to frequent illnesses. Family history is non-contributory. The patient is at the 2nd percentile for height and weight. Temperature is 38.7 C (101.7 F), pulse is 151/min, respirations are 36/min and blood pressure is 70/40 mmHg. Physical examination demonstrates white patches in the oral cavity and diffuse rales of the lungs bilaterally. Laboratory results are demonstrated below.

 Complete blood count 
 Leukocyte count  8,100 /mm3 
 Platelet count  300,000/mm3 
 Lymphocytes  5% 
 CD 19+  low 
 CD 3+  absent 
 IgG  220mg/dL 
 IgA  40 mg/dL 
 IgM  15 mg/dL 

Chest X-ray demonstrates bilateral diffuse interstitial infiltrates. Which of the following is the most likely diagnosis?

External References

First Aid








Autosomal recessive disorders

severe combined immunodeficiency p. 115

Bone marrow transplant

severe combined immunodeficiency p. 115

SCID (severe combined immunodeficiency disease) p. 96, 115

adenosine deaminase deficiency as cause p. 35

lymphopenia caused by p. 431

External Links


Severe combined immunodeficiency (SCID) is a severe form of primary immunodeficiency, caused by a genetic mutation that affects the development and function of white blood cells, which are responsible for fighting off infections. It may result from an X-linked recessive defect in IL-2R (interleukin-2 receptor) gamma chain or an autosomal recessive defect in adenosine deaminase deficiency. As a result, individuals with SCID are highly susceptible to infections, particularly bacterial and viral infections, and often present with failure to thrive, chronic diarrhea, thrush, and recurrent infections. Treatment involves HSCT (hematopoietic stem cell transplantation, avoiding live vaccines, antimicrobial prophylaxis, and isolation to prevent catching an infection.


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