Updated: 10/18/2018

Elastin

Topic
Review Topic
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Questions
4
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Evidence
6
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Overview
  •  Structure
    • rich in proline, lysine, glycine
      • unlike collagen, can exist in nonglycosylated forms
    • fibrillin protein binds to tropoelastin to form elastic fibers
      • Marfan's disease is caused by a defect in fibrillin  
        • presentation
          • long extremities including fingers
          • scoliosis
          • myopia and lens dislocations
            • upward (like a martian leaving for outer space)
              • as opposed to a downward dislocation in homocystinuria
          • mitral valve prolapse
          • ↑ for aortic aneurism
  • Function
    • is an elastic protein
      • found in tissues where stretch is needed
        • lungs, dermis of the skin, large arteries, elastic ligaments, vocal cords, ligamenta flava of vertebrae
        • desmosine interchain cross linking between lysine residues gives the protein its elastic stretch
    • degraded by elastase
      • α1-antitrypsin normally inhibits elastase
        • class of protease inhibitors
        • synthesized in the liver
      • excess elastase activity caused by α1-antitrypsin (AAT) deficiency
        • absent α1-globulin peak in serum protein electrophoresis
        • autosomal codominant inheritence
        • presentation
          • panacinar emphysema
            • worsened by smoking
            • early onset
              • smoking without AAT deficiency usually causes centriacinar emphysema
          • cirrhosis
Clinical Significance

Disease 

Comments

Marfan syndrome

  • Almost exclusively AD
  • Mutation in FBN gene
    • encodes fibrillin-1 gene on chromosome 15
  • Patients are susceptible to aortic disease, MVP, lens dislocation, scoliosis, pectus deformity, arachnodactyly

α1-antitrypsin deficiency

  • Autosomal codominant inheritence
  • α1-antitrypsin inhibits elastase
  • Can lead to panacinar emphysema and hepatic disease
 
   

Marfan’s syndrome

 

α1-antitrypsin deficiency

 

 

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Questions (4)
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.BC.32) A 26-year-old tall, thin woman is seen in the office. On exam you note upward dislocation of her lens as well as findings shown in Figure A. Cardiac auscultation reveals a mid-systolic click followed by a systolic murmur loudest at the apex. Which of the following describes the protein likely to be defective in this woman? Review Topic

QID: 100097
FIGURES:
1

Forms makeup of bone, skin, and tendons

30%

(75/251)

2

Lies in the actin groove

2%

(5/251)

3

Binds tropoelastin

42%

(105/251)

4

Made of polymerized dimers of tubulin

11%

(27/251)

5

Formed of repetitive Gly-Pro-X sequences

15%

(37/251)

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(M1.BC.17) Which of the following factors gives the elastin molecule the ability to stretch and recoil? Review Topic

QID: 100082
1

Hydroxylation of proline and lysine rich regions

16%

(27/168)

2

Cross-links between lysine residues

51%

(85/168)

3

Elastase activity

14%

(23/168)

4

Triple helix formation

13%

(22/168)

5

Cleavage of disulfide rich terminal regions

4%

(7/168)

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