questions 6

Severe Combined Immunodeficiency Disorder (SCID)

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Topic updated on 12/19/16 11:49am

Snapshot
  • A 2-month-old baby boy is brought in for an urgent visit to the pediatrician. He has had several ear infections in his short lifetime and now seems to be struggling with a cold. On physical exam, his tongue is noted to be coated with white film. His scalp and face are covered with a flaky dandruff-like substance. Immediately concerned, his pediatrician orders a chest radiograph, which shows absence of thymic shadow. Flow cytometry is ordered.
Introduction
  • Combined B- and T-cell disorder causing immunodeficiency
  • Life-threatening disease of recurrent infections
  • Pathogenesis
    • multiple variants found
    • most common is X-linked defective common gamma chain
      • found in IL-2R, IL-4R, and IL-7R
      • defective T-cell activation
    • autosomal recessive adenosine deaminase deficiency 
      • 2nd most common
      • ↑ deoxyadenosine, which is toxic to lymphocytes
      • ↓ DNA synthesis
    • autosomal recessive JAK3 deficiency
    • B-cells
      • decreased immunoglobulin production
    • T-cells
      • markedly decreased T-cells
Presentation
  • Symptoms
    • symptoms present < 3 months of age
    • failure to thrive
    • recurrent bacterial, viral, fungal, and protozoal infections  
    • chronic diarrhea 
  • Physical exam
    • may see thrush in mouth and diaper area
    • eczematous dermatitis
      • erythroderma (> 90% body surface area involvement)
    • severe seborrheic dermatitis
    • diffuse alopecia
    • absent lymphatic tissue, including tonsils and thymus
Evaluation
  • Diagnosis often delayed due to maternal IgG protecting baby in first few months of life
  • ↓ Lymphocyte count (< 3000/μL)
  • Chest radiography with no thymic shadow
  • Flow cytometry
    • absent T-cells
    • abnormal function of B-cells
Differential Diagnosis
  • Hypogammaglobulinemia
  • DiGeorge syndrome
  • Hyper-IgM syndrome
  • Ataxia-telangiectasia
Treatment
  • Bone marrow transplant
    • life-saving treatment
    • no concerns for allograft rejection
  • Gene therapy
Prognosis, Prevention, and Complications
  • Prognosis
    • without intervention, death by 2 years
    • patients < 6 months of age who receive transplant have the best outcomes
  • Complications
    • severe infection
    • death


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Qbank (4 Questions)

TAG
(M1.IM.5) A six-year old child presents for evaluation of a medical condition associated with recurrent infections. After reviewing all of the medical history, gene therapy is offered to treat a deficiency in adenosine deaminase (ADA). ADA deficiency is the most common autosomal recessive mutation in which of the following diseases? Topic Review Topic

1. DiGeorge Syndrome
2. Severe Combined Immunodeficiency
3. Hyper-IgM Syndrome
4. Wiskott-Aldrich Syndrome
5. Bruton's Agammaglobulinemia

PREFERRED RESPONSE ▶
TAG
(M1.IM.39) A 3-year-old Cuban-American male has a history of recurrent Pseudomonas and Candida infections. Laboratory analysis reveals no electrolyte abnormalities. Examination of his serum shows decreased levels of IgG and CT scan reveals the absence of a thymus. The child likely has: Topic Review Topic

1. Severe combined immunodeficiency syndrome
2. X-linked agammaglobinemia
3. DiGeorge syndrome
4. Isolated IgA deficiency
5. Common variable immunodeficiency

PREFERRED RESPONSE ▶
TAG
(M1.IM.40) A 2-year-old Caucasian male presents with recurrent diaper rash and oral thrush. He has also experienced recurrent episodes of otitis media from repeat Streptoccous pneumoniae. What disease is the child suffering from? Topic Review Topic

1. X-linked agammaglobulinemia
2. Isolated IgA deficiency
3. Severe combined immunodeficiency
4. DiGeorge syndrome
5. MHC class II deficiency

PREFERRED RESPONSE ▶
TAG
(M1.IM.74) A 4-month-old boy is brought to the pediatrician by his foster mother. She has no knowledge of his birth history but states that, for the past 3 months, he has had multiple viral and bacterial infections in addition to repeated bouts of diarrhea. On exam, the pediatrician observes the findings demonstrated in Figure A. The pediatrician tells the foster mother he is concerned the child may have an immunodeficiency. Levels of which of the following would be most likely to be reduced in this patient? Topic Review Topic
FIGURES: A          

1. Inosine
2. Adenosine
3. Cytosine
4. Thymine
5. Uracil

PREFERRED RESPONSE ▶
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