Updated: 2/5/2018

Glycogen Storage Disorders

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  • A 16-year-old male presents with fatigue and muscle cramps. He recently tried out for the basketball team and has found himself exhausted soon after performing high-intensity sprints. When resting briefly, he said he gets his “second wind.” After practice, he noticed that his urine was brown. Laboratory results are significant for an elevated creatine kinase level of 1,423 U/L (normal < 200 U/L). There was no increase of lactate on forearm nonischemic testing. (McArdle disease)

Introduction
  • Glucose is a crucial source of energy for proper cellular functioning
    • essential for cells without mitochondria
      • e.g., erythrocytes (RBCs)
    • greatly preferred by neurons
    • important energy source for exercising muscle
      • needed for anaerobic glycolysis
  • Serum glucose sources
    • glycogen breakdown
    • gluconeogenesis
    • diet
  • Glycogen storage disorders (GSD)
    • genetic mutations → abnormal glycogen accumulation in certain tissues
      • liver and muscle
GSD Defect Findings Management

Von Gierke disease (type I)

  • Hepatic glucose-6-phosphatase
  • Autosomal recessive
  • Usually presenting at 3 - 6 months of age
  • Hepatomegaly
  • Signs of hypoglycemia
    • seizure
  • "Doll-like" face
  • Poor growth
  • ↑ uric acid
    • due to impaired renal clearance and increased production
    • gout
  • ↑ lactic acid
  • ↑ triglycerides
    • xanthomas
    • pancreatitis
  • Dietary management
    • frequent small meals
    • avoid fructose, galactose, and sucrose
      • to prevent lactic acidosis

Pompe disease (type II)

  • Lysosomal α(1,4)-glucosidase
  • Autosomal recessive
  • Infantile form 
    • cardiomegaly
    • generalized muscle hypotonia
    • respiratory distress
  • Juvenile and adult form
    • skeletal myopathy
    • delayed-gross motor development
    • limb-girdle weakness
    • respiratory issues
  • Enzyme replacement therapy
    • alglucosidase alfa

Cori disease (type III)

  • Glycogen debranching enzyme
  • Autosomal recessive
  • Most cases involve the muscle and liver
  • Hepatomegaly
  • Mild hypoglycemia
    • intact gluconeogenesis
  • Symptomatic treatment

McArdle disease (type V)

  • Muscle glycogen phosphorylase
  • Autosomal recessive
  • Affects the skeletal muscle
  • No elevation of blood lactate during forearm exercise test
  • ↑ creatine kinase
  • Muscle cramp, fatigue, myalgias, myoglobinuria
  • "Second wind" phenomenom
    • rapid relief of fatigue and myalgia
    • secondary to increase blood flow, improved free fatty acid delivery, and liver glucose utilization
  • Sucrose before exercise may improve symptoms
 
Evaluation
  • Von Gierke disease (type I)
    • laboratory testing
      • fastic hypoglycemia
      • elevated lactic acid, triglycerides, uric acid
    • genetic testing
      • preferred over liver biopsy
    • liver biopsy
  • Pompe disease (type II)
    • laboratory testing
      • elevated creatine kinase, lactic acid
    • acid α-glucosidase testing
  • Cori disease (type III)
    • labs depend on organ involvement
  • McArdle disease (type V)
    • laboratory testing
      • elevated creatine kinase (> 1000 U/L)
    • forearm nonischemic testing
      • elevated ammonia, no elevation in lactate
      • no longer recommended
    • histology
      • most cases show no evidence of enzyme activity in muscle fiber when staining for myophosphorylase
    • genetic testing
 

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Questions (1)
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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