Updated: 5/13/2019

Neurofibromatosis Type I

Topic
Review Topic
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Questions
4
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Evidence
4
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Snapshot
  • A 3-year-old female presents with an abnormal "dark spot" in certain parts of the body. The mother reports that these spots began to develop sometime during the last year, but have progressively worsened. The mother also states that her husband has similar skin findings and a history of seizures. On exam, 7-8 uniformly hyperpigmented macules are noted on the chest, back, and buttock. There is freckling in the axilla and inguinal region.
Introduction
  • Neurofibromatosis type I (von Recklinghausen disease)
    • most common type of neurofibromatosis
    • autosomal dominant inheritance
      • mutation in NF1 gene on chromosome 17
        • NF1 gene codes for neurofibromin
          • tumor suppressor that inhibits ras activity via stimulating GTPase
    • variable presentation
  • Epidemiology
    • ~50% of cases are inherited
      • the rest are sporadic mutations
    • overall risk of malignancy is increased
Presentation
  • Physical exam 
    • café-au-lait macules 
    • neurofibromas
      • benign nerve sheath tumor
    • Lisch nodule
      • iris hamartoma
    • optic pathway glioma
    • axillary an inguinal freckling
    • hypertension
    • macrocephaly
Evaluation
  • Clinical diagnosis
    • e.g., presence of café-au-lait macules, neurofibromas, Lisch nodules, freckling, etc
  • Genetic analysis
    •  rarely indicated
Differential Diagnosis
  • Neurofibromatosis type II
  • McCune-Albright syndrome
  • MEN 2b
  • Familial multiple café-au-lait spots
Treatment
  • Dependent on clinical manifestations
    • e.g., surgical intervention for tumor excision
  • Annual history and physical for children
    • for adults, depends on disease severity
Prognosis, Prevention, and Complications
  • Prognosis
    • increased mortality
  • Prevention
    • genetic counseling
  • Complications
    • increased lifetime cancer risk
 

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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.NE.0) A 50-year-old male presents to the dermatologist for a large, soft, cutaneous nerve sheath tumor on his right eyelid resulting in a vision deficit. On physical exam, hyperpigmented macules and numerous other tumors can be seen across his body along with freckling in the inguinal and axillary areas (Figure A & B). His past medical history is significant for loss of vision in his left eye due to an optic glioma at the age of 20. His family history is notable for several members on his mother's side (grandmother, mother, uncle, and brother) having a similar presentation. Genome analysis reveals that the gene is located on chromosome 17. Which of the following genes is most likely mutated? Review Topic

QID: 107027
FIGURES:
1

VHL

8%

(4/48)

2

RB

0%

(0/48)

3

NF-1

92%

(44/48)

4

WT-1

0%

(0/48)

5

BRCA-1

0%

(0/48)

M1

Select Answer to see Preferred Response

PREFERRED RESPONSE 3

(M1.NE.17) A 14-year-old boy presents as a new patient to your practice. While conducting your physical exam, you observe the findings depicted in Figures A and B. Which of the following additional findings would most likely be found in this patient? Review Topic

QID: 105017
FIGURES:
1

The presence of ash-leaf spots

15%

(17/111)

2

A family history of seizures and mental retardation

8%

(9/111)

3

Facial angiofibromas

19%

(21/111)

4

Iris hamartomas

52%

(58/111)

5

A white tuft of scalp hair since birth

5%

(5/111)

M1

Select Answer to see Preferred Response

PREFERRED RESPONSE 4

(M1.NE.72) A 27-year-old Caucasian man presents for a routine visit to his primary care physician. He does not have any complaints at this time. On physical exam he is noted to have numerous firm, rubbery nodules of varying sizes on his back (see Figure A). He also has small darkly pigmented spots on his irises as well as a hyperpigmented, macular skin lesion measuring 3x5 cm on his right medial thigh. Which of the following is a complication of this patient's genetic condition? Review Topic

QID: 106525
FIGURES:
1

Bilateral acoustic schwannomas

18%

(9/51)

2

Cardiac rhabdomyomas

10%

(5/51)

3

Optic gliomas

63%

(32/51)

4

Retinal hemangioblastomas

6%

(3/51)

5

Renal angiomyolipomas

4%

(2/51)

M1

Select Answer to see Preferred Response

PREFERRED RESPONSE 3
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