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Snapshot
  • A 3-year-old boy presents to his pediatrician for fever and a cough. He has a history of recurrent pneumonia and chronic diarrhea. His mother states that he has 6-8 foul smelling stools per day. His temperature is 101.0°F (38.3°C), blood pressure is 95/55 mmHg, pulse is 120/min, and respirations are 28/min. Physical exam is notable for scattered rhonchi in the bilateral lung fields with hepatomegaly. Sweat chloride testing is elevated on 2 separate occasions.
Introduction
  • Definition
    • autosomal recessive exocrinopathy 
  • Epidemiology
    • incidence
      • most commonly affects Caucasians
      • ΔF508 mutation is the most common mutation
  • Etiology
    • an autosomal recessive mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, a chloride channel, on chromosome 7
  • Pathogenesis
    • a defect in the CFTR gene leads to impaired chloride and water transport
      • this causes viscous secretions in the
        • respiratory tract
        • exocrine pancreas
        • sweat glands
        • intestines
        • genitourinary tract
  • Associated conditions
    • nasal polyposis
    • infertility in men and subfertility in women
    • pancreatic insufficiency
  • Prognosis
    • most of the morbidity and mortality associated with this condition is secondary to pulmonary disease
Presentation
  • Symptoms 
    • a productive cough
    • respiratory symptoms are more prominent in adulthood  
      • recurrent pulmonary infections  
        • S. aureus is more common in pediatric patients (treat with vancomycin)
        • Pseudomonal spp. are more common in adults (treat with amikacin, ceftazidime, and ciprofloxacin)
      • chronic sinusitis
      • chronic productive cough
      • dyspnea on exertion
      • bronchiectasis
    • gastrointestinal symptoms are more prominent in infancy
      • chronic and frequent diarrhea
        • greasy stool with flatulence from malabsorption secondary to pancreatic insufficiency
        • can lead to rectal prolapse
      • meconium ileus in infants (15%) 
  • Physical exam
    • failure to thrive (50%)
    • respiratory compromise (50%)
    • "salty taste"
    • cyanosis
    • digital clubbing
    • rhonchi
    • rales
    • hyperresonance to percussion
    • nasal polyposis
    • infertility 
Studies
  • Making the diagnosis is based on
    • clinical symptoms that are consistent with cystic fibrosis in at least 1 organ system
    • evidence of CFTR gene dysfunction
      • elevated sweat chloride test 
        • ≥ 60 mmol/L on 2 occasions
          • sufficient to confirm the diagnosis in patients with clinical symptoms suggestive of cystic fibrosis
      • abnormal nasal potential difference
      • genetic testing
Treatment
  • Conservative
    • chest physical therapy
      • indication
        • to clean airways and decrease the risk of airway infection
    • fat-soluble vitamin supplementation
      • indication
        • to decrease the risk of fat-soluble vitamin deficiency
    • vaccinations
      • indication
        • used as a preventative measure for pulmonary infection
      • vaccinations
        • influenza
        • pneumococcal
  • Medical
    • antibiotics 
      • indication
        • to treat and prevent pulmonary infection
    • pancreatic enzyme replacement therapy
      • indication
        • to manage pancreatic insufficiency
Complications
  • Bronchopulmonary
    • lower airway infection (e.g., Pseudomonas)
    • bronchiectasis
  • Gastrointestinal
    • cholestasis
    • intestinal atresia
    • malnutrition and malabsorption
    • intestinal impaction
    • meconium ileus
  • Hepatobiliary
    • pancreatic insufficiency
  • Endocrine
    • diabetes
    • infertility due to congenital absence of the vas deferens  
    • decreased fertility in females
 
 

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Questions (7)
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

(M2.PL.29) A 14-hour-old boy has failed to pass stool and is vomiting greenish fluid. He was born at 40 weeks gestation with no complications during delivery or pregnancy. His temperature is 97.6°F (36.4°C), blood pressure is 64/34 mmHg, pulse is 140/min, respirations are 33/min, and oxygen saturation is 98% on room air. The child is currently breastfeeding and appears irritable. Physical exam is notable for a distended and non-tender abdomen. Rectal exam is unremarkable. An abdominal radiograph is shown in Figure A. What is the most likely diagnosis? Review Topic

QID: 105427
FIGURES:
1

Cystic fibrosis

14%

(13/92)

2

Hirschsprung disease

2%

(2/92)

3

Jejunal atresia

2%

(2/92)

4

Pyloric stenosis

34%

(31/92)

5

Tracheoesophageal fistula

47%

(43/92)

M2

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PREFERRED RESPONSE 1
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(M2.PL.4798) A 2-day-old male is evaluated in the hospital nursery for vomiting. He has vomited three times in the last four hours and now shows little interest in feeding. His mother describes his last episode of emesis as green in color. The patient is sleeping and urinating well, but has not yet passed meconium. The patient was born at 35 weeks gestation to a 42-year-old gravida 3. The patient’s mother received sporadic prenatal care and did not undergo any prenatal testing. His birth weight was 2.80 kg (6 lb 3 oz), and his current weight is 2.30 kg (5 lb 1 oz). The patient’s temperature is 98.8°F (37.1°C), blood pressure is 56/41 mmHg, pulse is 137/min, and respirations are 32/min. On physical exam, he is in mild distress. His abdomen is soft and distended. Digital rectal exam reveals an absence of stool in the rectal vault. His abdominal radiograph can be seen in Figure A. A contrast enema is performed and can be seen in Figure B.

Which of the following additional findings would most likely be found in this patient? Review Topic

QID: 109245
FIGURES:
1

Bronchiectasis

6%

(1/18)

2

Absence of the vas deferens

72%

(13/18)

3

Diaphragmatic hernia

0%

(0/18)

4

Patent ductus arteriosus

0%

(0/18)

5

Single transverse palmar crease

22%

(4/18)

M2

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PREFERRED RESPONSE 2

(M2.PL.4798) A 46-hour-old female is evaluated in the hospital nursery for difficulty feeding. Her mother reports that breastfeeding was going well for the first several feeds, but the patient now seems less interested in feeding and refuses to latch. A few minutes later, the patient has two episodes of biliary emesis. She has not yet had a bowel movement. The patient was born at 37 weeks gestation to a 39-year-old gravida 4. The pregnancy was uncomplicated. The patient’s family history is significant for a maternal uncle who died in his late 20's due to pulmonary disease. The patient’s father was adopted, and little is known about his biological family. The patient’s three older siblings are healthy. The patient’s temperature is 97.8°F (36.6°C), blood pressure is 62/44 mmHg, pulse is 140/min, and respirations are 36/min. On physical exam, the patient is crying, and her abdomen is markedly distended. There is no stool in the rectal vault on digital rectal exam. An abdominal radiograph is performed and can be seen in Figure A. A contrast enema is scheduled.

Which of the following additional tests should be performed on this patient? Review Topic

QID: 109246
FIGURES:
1

Abdominal ultrasound

0%

(0/0)

2

Karyotype analysis

0%

(0/0)

3

Rectal suction biopsy

0%

(0/0)

4

Sweat testing

0%

(0/0)

5

Upper gastrointestinal series

0%

(0/0)

M2

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PREFERRED RESPONSE 4
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