Updated: 5/1/2017

HMP Shunt

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Overview

  • Function 
    • generate NADPH
      • required for FA synthesis, steroid synthesis, reduction of oxidizing agents (H2O2 see figure)
    • provide ribose 5-phosphate
      • required for nucleotide synthesis
  • Pathway
    • occurs in cytoplasm of all cells
    • no ATP consumed or generated
    • 2 phases
      • oxidative
        • produces NADPH
        • glucose 6-phosphate (G6P) → 6-phosphogluconate
          • catalyzed by glucose 6-phosphate dehydrogenase (G6PDH)
            • rate limiting step
            • activated by NADP+, insulin
            • inhibited by NADPH
        • irreversible
      • nonoxidative
        • exchanging intermediate substrates between glycolysis and HMP shunt
          • catalyzed by transketolase
            • requires thiamine
        • reversible
  • Clinical relevance
    • glucose-6-phosphate dehydrogenase (G6PDH) deficiency   
      • pathophysiology
        • ↓ NADPH production
          • cells (specifically RBCs) lose protection against oxidizing agents
            • cannot regenerate glutathione
        • XR
        • most common human enzyme deficiency
        • ↑ prevalence among blacks
          • ↑ malarial resistance
            • by shortening the circulation life of RBCs
              • Plasmodium does not have enough time for life span
            • plasmodium does not have defense against free radicals
              • ↑ in free radicals kills parasite
      • presentation
        • episodic hemolytic anemia
          • intravascular hemolysis
          • normocytic
          • 2-3 days post precipitating stress
            • foods
              • fava beans
                • common in Mediterranean foods
                • presentation
                  • pallor, hemoglobinuria 24-48 post ingestion
            • drugs
              • sulfonamides, primaquine, antituberculosis drugs
            • infection
              • free radicals generated by the immune system
        • Heinz bodies  
          • oxidized hemoglobin that precipitates within RBCs
        • bite cells  
          • result from the phagocytic removal of Heinz bodies by macrophages 
        • back pain
      • test
        • active hemolysis screen
          • Heinz body prep 
 

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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
Calculator

(M1.BC.74) A 32-year-old male with HIV presents to his physician with complaints of shortness of breath and fatigue. He has a history of being non-compliant with his HAART regimen, and his CD4 count is found to be 149. The physician obtains a chest radiograph, which is shown in Figure A. Further workup demonstrates that the patient is infected with the organism demonstrated in Figure B. The physician prescribes the first-line treatment for this infection. One day later, the patient returns complaining of severe weakness and dark colored urine. On exam, the physician notes that the patient is jaundiced, and a peripheral blood smear demonstrates the findings shown in Figure C. Which of the following would most mimic this patient's condition? Review Topic

QID: 106610
FIGURES:
1

Glutathione reductase deficiency

60%

(6/10)

2

Galactokinase deficinecy

10%

(1/10)

3

Ornithine transcarbamolyase deficiency

20%

(2/10)

4

Carnitine deficiency

0%

(0/10)

5

Cystathionine synthase deficiency

0%

(0/10)

M1

Select Answer to see Preferred Response

PREFERRED RESPONSE 1

(M1.BC.4707) A 12-year-old boy presents to the emergency department with fatigue and back pain. He has also had tea-colored urine over the last 24 hours. Upon being asked about changes to his routine over the last week, he remembers running a 5K, trying alcohol with a friend, and having a large meal at a friend's house with ingredients that he did not recognize. On physical exam he appears to be pale with conjunctival pallor. Labs are as follows:

Hemoglobin: 11 g/dL
Hematocrit: 32%
Mean Corpuscular Volume: 88 fL

Peripheral blood smear findings are shown in Figure A. An enzyme defect in which of the following pathways is likely responsible for this patient's symptoms? Review Topic

QID: 108445
FIGURES:
1

Amino acid synthesis

3%

(7/202)

2

Glycolysis

16%

(32/202)

3

Hemoglobin assembly

8%

(16/202)

4

Hexose mono-phosphate (HMP) shunt

58%

(117/202)

5

Porphyrin synthesis

12%

(24/202)

M1

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PREFERRED RESPONSE 4
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(M1.BC.22) A 55-year-old African American lawyer presents to your office with complaints of fatigue, back pain and dark urine that he notices in the morning when he wakes up. The patient is well known to you. He frequently travels to Bangkok where he has admitted to having unprotected sex. You have treated him in the past for chlamydia, gonorrhea and syphilis. This patient has a family history of sickle cell disease in 4 of his brothers. He has a past medical history of HIV and his most recent CD4 count was 147 cells/µL. His current medications include lisinopril, glyburide, metformin, ibuprofen, and buspirone. Appropriate prophylactic measures were taken one week ago account for his low CD4 count and his traveling. The patient's CBC demonstrates:

Hemoglobin: 9 g/dL
Hematocrit: 32%
White blood cell count: 3,600 cells/µL
Platelets: 155,000/µL

A peripheral blood smear is shown in Figure A. A chest radiograph is shown in Figure B.

Which of the following is the best explanation for this patient's symptoms? Review Topic

QID: 100087
FIGURES:
1

Decreased levels of CD55 and CD59

15%

(20/135)

2

Osteomyelitis of the vertebral column

11%

(15/135)

3

Defective conversion of glucose-6-phosphate to 6-phosphogluconate

60%

(81/135)

4

Side-effect of rifampin treatment

10%

(14/135)

5

Splenic insufficiency

3%

(4/135)

M1

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PREFERRED RESPONSE 3
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