Updated: 8/22/2017

Severe Combined Immunodeficiency Disorder (SCID)

Topic
Review Topic
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Questions
6
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Evidence
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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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Questions (6)
Lab Values
Blood, Plasma, Serum Reference Range
ALT 8-20 U/L
Amylase, serum 25-125 U/L
AST 8-20 U/L
Bilirubin, serum (adult) Total // Direct 0.1-1.0 mg/dL // 0.0-0.3 mg/dL
Calcium, serum (Ca2+) 8.4-10.2 mg/dL
Cholesterol, serum Rec: < 200 mg/dL
Cortisol, serum 0800 h: 5-23 μg/dL //1600 h:
3-15 μg/dL
2000 h: ≤ 50% of 0800 h
Creatine kinase, serum Male: 25-90 U/L
Female: 10-70 U/L
Creatinine, serum 0.6-1.2 mg/dL
Electrolytes, serum  
Sodium (Na+) 136-145 mEq/L
Chloride (Cl-) 95-105 mEq/L
Potassium (K+) 3.5-5.0 mEq/L
Bicarbonate (HCO3-) 22-28 mEq/L
Magnesium (Mg2+) 1.5-2.0 mEq/L
Estriol, total, serum (in pregnancy)  
24-28 wks // 32-36 wks 30-170 ng/mL // 60-280 ng/mL
28-32 wk // 36-40 wks 40-220 ng/mL // 80-350 ng/mL
Ferritin, serum Male: 15-200 ng/mL
Female: 12-150 ng/mL
Follicle-stimulating hormone, serum/plasma Male: 4-25 mIU/mL
Female: premenopause: 4-30 mIU/mL
midcycle peak: 10-90 mIU/mL
postmenopause: 40-250
pH 7.35-7.45
PCO2 33-45 mmHg
PO2 75-105 mmHg
Glucose, serum Fasting: 70-110 mg/dL
2-h postprandial:<120 mg/dL
Growth hormone - arginine stimulation Fasting: <5 ng/mL
Provocative stimuli: > 7ng/mL
Immunoglobulins, serum  
IgA 76-390 mg/dL
IgE 0-380 IU/mL
IgG 650-1500 mg/dL
IgM 40-345 mg/dL
Iron 50-170 μg/dL
Lactate dehydrogenase, serum 45-90 U/L
Luteinizing hormone, serum/plasma Male: 6-23 mIU/mL
Female: follicular phase: 5-30 mIU/mL
midcycle: 75-150 mIU/mL
postmenopause 30-200 mIU/mL
Osmolality, serum 275-295 mOsmol/kd H2O
Parathyroid hormone, serume, N-terminal 230-630 pg/mL
Phosphatase (alkaline), serum (p-NPP at 30° C) 20-70 U/L
Phosphorus (inorganic), serum 3.0-4.5 mg/dL
Prolactin, serum (hPRL) < 20 ng/mL
Proteins, serum  
Total (recumbent) 6.0-7.8 g/dL
Albumin 3.5-5.5 g/dL
Globulin 2.3-3.5 g/dL
Thyroid-stimulating hormone, serum or plasma .5-5.0 μU/mL
Thyroidal iodine (123I) uptake 8%-30% of administered dose/24h
Thyroxine (T4), serum 5-12 μg/dL
Triglycerides, serum 35-160 mg/dL
Triiodothyronine (T3), serum (RIA) 115-190 ng/dL
Triiodothyronine (T3) resin uptake 25%-35%
Urea nitrogen, serum 7-18 mg/dL
Uric acid, serum 3.0-8.2 mg/dL
Hematologic Reference Range
Bleeding time 2-7 minutes
Erythrocyte count Male: 4.3-5.9 million/mm3
Female: 3.5-5.5 million mm3
Erythrocyte sedimentation rate (Westergren) Male: 0-15 mm/h
Female: 0-20 mm/h
Hematocrit Male: 41%-53%
Female: 36%-46%
Hemoglobin A1c ≤ 6 %
Hemoglobin, blood Male: 13.5-17.5 g/dL
Female: 12.0-16.0 g/dL
Hemoglobin, plasma 1-4 mg/dL
Leukocyte count and differential  
Leukocyte count 4,500-11,000/mm3
Segmented neutrophils 54%-62%
Bands 3%-5%
Eosinophils 1%-3%
Basophils 0%-0.75%
Lymphocytes 25%-33%
Monocytes 3%-7%
Mean corpuscular hemoglobin 25.4-34.6 pg/cell
Mean corpuscular hemoglobin concentration 31%-36% Hb/cell
Mean corpuscular volume 80-100 μm3
Partial thromboplastin time (activated) 25-40 seconds
Platelet count 150,000-400,000/mm3
Prothrombin time 11-15 seconds
Reticulocyte count 0.5%-1.5% of red cells
Thrombin time < 2 seconds deviation from control
Volume  
Plasma Male: 25-43 mL/kg
Female: 28-45 mL/kg
Red cell Male: 20-36 mL/kg
Female: 19-31 mL/kg
Cerebrospinal Fluid Reference Range
Cell count 0-5/mm3
Chloride 118-132 mEq/L
Gamma globulin 3%-12% total proteins
Glucose 40-70 mg/dL
Pressure 70-180 mm H2O
Proteins, total < 40 mg/dL
Sweat Reference Range
Chloride 0-35 mmol/L
Urine  
Calcium 100-300 mg/24 h
Chloride Varies with intake
Creatinine clearance Male: 97-137 mL/min
Female: 88-128 mL/min
Estriol, total (in pregnancy)  
30 wks 6-18 mg/24 h
35 wks 9-28 mg/24 h
40 wks 13-42 mg/24 h
17-Hydroxycorticosteroids Male: 3.0-10.0 mg/24 h
Female: 2.0-8.0 mg/24 h
17-Ketosteroids, total Male: 8-20 mg/24 h
Female: 6-15 mg/24 h
Osmolality 50-1400 mOsmol/kg H2O
Oxalate 8-40 μg/mL
Potassium Varies with diet
Proteins, total < 150 mg/24 h
Sodium Varies with diet
Uric acid Varies with diet
Body Mass Index (BMI) Adult: 19-25 kg/m2
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(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? Review Topic

QID: 100461
1

X-linked agammaglobulinemia

24%

(48/196)

2

Isolated IgA deficiency

9%

(18/196)

3

Severe combined immunodeficiency

51%

(99/196)

4

DiGeorge syndrome

10%

(19/196)

5

MHC class II deficiency

2%

(4/196)

M1

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PREFERRED RESPONSE 3
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(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? Review Topic

QID: 106688
FIGURES:
1

Inosine

35%

(51/147)

2

Adenosine

40%

(59/147)

3

Cytosine

6%

(9/147)

4

Thymine

14%

(20/147)

5

Uracil

4%

(6/147)

M1

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PREFERRED RESPONSE 1

(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: Review Topic

QID: 100460
1

Severe combined immunodeficiency syndrome

56%

(19/34)

2

X-linked agammaglobinemia

6%

(2/34)

3

DiGeorge syndrome

32%

(11/34)

4

Isolated IgA deficiency

0%

(0/34)

5

Common variable immunodeficiency

0%

(0/34)

M1

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PREFERRED RESPONSE 1

(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? Review Topic

QID: 100426
1

DiGeorge Syndrome

4%

(2/47)

2

Severe Combined Immunodeficiency

72%

(34/47)

3

Hyper-IgM Syndrome

0%

(0/47)

4

Wiskott-Aldrich Syndrome

9%

(4/47)

5

Bruton's Agammaglobulinemia

13%

(6/47)

M1

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PREFERRED RESPONSE 2
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