Updated: 3/13/2018

Friedreich Ataxia

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Snapshot
  • A 23 year old male with a past medical history of diabetes mellitus presents with muscle weakness, staggering gait with frequent falling, dysarthria and a curvature in his upper spine.  On physical exam the patient is noted to have marked muscle weakness (2/5 in upper and lower extremitites), a loss of deep tendon reflexes, nystagmus as well as pes cavus and kyphoscoliosis.  Patient had a recent ED visit for pneumonia and a bedside ultrasound demonstrated a hypertrophic cardiomyopathy.
Introduction
  • friedrichsCongenital impairment of mitochondrial function leading to cerebellar and spinal cord degeneration
    • due to a mutation in the frataxin gene which is essential for mitochondrial iron regulation
  • Presents in childhood
  • Autosomal recessive
    • trinucleotide repeat disorder (GAA) on chromosome 9
Presentation
  • Symptoms 
    • staggering gait
    • frequent falling 
    • wheelchair bound by first decade
    • insulin resistance
    • dysarthria
  • Physical exam
    • nystagmus
    • neurological sequelae
      • decreased vibratory and proprioceptive senses
      • muscle weakness
      • loss of deep tendon reflexes
    • musculoskeletal deformities 
      • pes cavus
      • hammer toes
      • kyphoscholiosis
Prognosis and Complications
  • Death in adolescence most commonly due to cardiac arrhythmia
    • a sequlae of hypertrophic cardiomyopathy
 

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Questions (6)
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.NE.72) An 8-year-old boy is brought to the pediatrician because his mother is concerned about recent behavioral changes. His mother states that she has started to notice that he is slurring his speech and seems to be falling more than normal. On exam, the pediatrician observes the boy has pes cavus, hammer toes, and kyposcoliosis. Based on these findings, the pediatrician is concerned the child has a trinucleotide repeat disease. Which of the following trinucleotide repeats is this child most likely to possess? Review Topic

QID: 106528
1

CGG

10%

(2/21)

2

GAA

71%

(15/21)

3

CAG

10%

(2/21)

4

CTG

5%

(1/21)

5

GCC

5%

(1/21)

M1

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PREFERRED RESPONSE 2

(M1.NE.101) A 4-year-old male presents with a 1-year history of swaying while walking and recent episodes of tripping when ambulating. He has trouble trying to sit and get up from chairs, as well as walking up the stairs to his bedroom. On physical exam, the pediatrician notices nystagmus, absent deep tendon reflexes, significant loss of vibratory and proprioceptive sensation in his extremities, pes cavus, and slight kyphoscoliosis. A blood sample is sent for DNA sequencing and the results show a significant expansion of the trinucleotide GAA on chromosome 9. Which of the following diseases displays a similar mode of inheritance as the disease affecting this patient? Review Topic

QID: 107002
1

Osteogenesis imperfecta

4%

(1/24)

2

Von Gierke's disease

42%

(10/24)

3

Menke's disease

21%

(5/24)

4

Fragile X syndrome

33%

(8/24)

5

Leber hereditary optic neuropathy

0%

(0/24)

M1

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PREFERRED RESPONSE 2
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(M1.NE.30) An 8-year-old boy is referred to your neurology clinic with the chief complaint of "trouble walking." His mother believes her son's condition has gradually worsened over the past several months with the recent development of difficulty coordinating his arms. Physical examination is notable for an ataxic gait, nystagmus, and mild dysarthria. You also observe the findings in Figure A on musculoskeletal examination. His mother believes that her husband's brother suffered from similar complaints and passed away at the age of 37 years. Which physical exam findings would you statistically most likely find in this patient's 3-year-old brother? Review Topic

QID: 101694
FIGURES:
1

Systolic ejection murmur

11%

(8/71)

2

Telangiectasia

13%

(9/71)

3

Mental retardation

4%

(3/71)

4

Pes cavus

31%

(22/71)

5

Normal physical exam

39%

(28/71)

M1

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PREFERRED RESPONSE 5
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