1. Clinical Experience and Long-term Management
Krabbe Disease
Clinical Experience and
Long-term Management

2. Sphingolipids

3. Galactosylceramide -galactosidase Arylsulfatase A
-Galctosidase
Ceramide
Galactosylcerebroside
Galactosylceramide -galactosidase
Krabbe disease
Arylsulfatase A
Metachromatic leukodystrophy
Sulfatide
SO4
Glucocerebroside
Farber disease
Ceramidase
Sphingosine
Fatty acid

4. Krabbe Disease Galacotoceramide β-galactosidase deficiency
Also called Globoid Cell Leukodystrophy
Infantile form (85 – 90%): onset at 6 months and death by 2 years
Extreme irritability
Spastic quadriparesis
Blindness with optic atrophy
CNS infiltration with globoid cells (inflammatory reaction)
Late onset form (10 – 15%): onset between 1 year and 5th decade

5. Newborn Screening of Krabbe Disease Began
2006 New York State
Newborn Screening of
Krabbe Disease Began

6. Referred infants: After NBS Screening
Confirmatory Enzyme Analysis (Dr. David A. Wenger)
Consult with Geneticist/ Child Neurologist
Draw blood sample – e.g. HLA typing
If enzyme test affirms Krabbe disease likely..
Exam
CSF protein
MRI
Nerve conduction, BAER, VER, and other studies
recommend periodic evaluation, depending on dx lab enzyme activity level
A point system is used, if 4 or more points:
Consideration given to receive cord blood treatment

7. Referred infants - Risk categories
GALC ACTIVITY RISK CATEGORY
nmol/hr/mg protein
High
Moderate
Eliminated low risk category Jan. 1, 2012
> 0.3 * No Risk
Note that infants found with 2 or more mutations and > 0.3 activity, will be categorized as at moderate risk.
Courtesy of Dr. P. Duffner

8. CRITERIA FOR HCT REFERRAL
Consider Transplantation for scores > 4 Points
Points
Abnormal Neurologic Exam
Abnormal MRI
Abnormal LP (Increased Protein) 2
Abnormal NCV
Abnormal BAER
Abnormal VER
30 KB Homozygous Deletion 8 8

9. New York State Newborn Screening for Krabbe Disease August 7, 2006 to May 31, 2012
Dried
Blood
Spot
1,556,172 Screened for low GALC Activity
Threshold activity ≤12% daily mean
High Throughput MS/MS
Dried
Blood
Spot
DNA sequencing started
sequencing completed
191 low activity polymorphisms
Venous
Blood &
Follow up
261→ Counseling and
Venous Confirmation
25 mod. risk
3H labeled - natural substrate
ηmol/h/mg protein
ηmol/h/mg protein
12 high risk
(4 KD*)
8 “healthy” up to 60 mos
3 → HCT, 1 dead, 1 chronic hemolytic anemia
1 → refused HSCT
< 0.15 ηmol/h/mg protein
*4KD Predicted to have infantile form
Based on genotype and neurodiagnostic testing

10. Annual Assessments Center Visits
Neurologic Assessment
Neurologic Testing
(LP, MRI, BAER, VER, NCT)—high and moderate risk babies only
Cognitive Testing
Courtesy of Dr. P. Duffner

11. Outcomes Study Phone call interviews: 4, 8, 12, 18, 24 months of age
--Ages and Stages Questionnaire
--Wee FIM 0-3
--Warner IDEA FS
Early intervention referral as needed
Comparison with annual Bayley III
Courtesy of Dr. P. Duffner

12. EVALUATION SCHEDULE
Neurological Evaluation Neurodiagnostic Year 1 Q Month Q 3 Months High Risk Year 2 Q 3 Months Q 6 Months Year 1 Q 3 Months Annual Mod Risk Year 2 Q 3 Months Annual Year 1 Q 6 Months Annual* Low Risk Year 2 Q 6 Months Annual* 12 12

13. Referred Infants: Follow-up Schedule
Low rate of compliance (unsure of percentage):
Neurodiagnostic testing is evasive
Cultural issues
Asking families to participate in long-term follow-up activities when the child is considered healthy
Compliance with phone call interviews is much better (unsure of percentage)
Need some other less evasive tool to assess and monitor risk of biochemically enzyme deficient individuals.

14. From Screening: High-risk, infantile KD
1. g.30 Kb deletion // p.X670Qext42 [TP]
9.9% 0.01 nmol/hr/mg protein
2. g.30Kb deletion // g.30 Kb deletion [TP]
10.9% 0.05 nmol/hr/mg protein
3. g.30Kb deletion // g.30 Kb deletion [parents refused TP; symptomatic]
7.6% 0.02 nmol/hr/mg protein
g.30Kb deletion // p.A5P/ G360DfsX2 [TP]
5.6% 0.12 nmol/hr/mg protein

15. High Risk Children/Asymptomatic
p.A5P / p.D232N / p.Y303C // p.A5P / p.D232N / p.Y303C
6.1% 0.06 nmol/hr/mg protein
p.A5P / p.D232N / p.Y303C / p.I546T // p.D556X
8.3% 0.12 nmol/hr/mg protein
Genotype/phenotype correlations are very difficult;
Examples of point mutations associated with infantile KD: Y551S, T513M , Y287F, R380L
Major difficulty: If low GALC activity and DNA variants of unknown significance, how do we determine who is a candidate for cord blood transplant? Currently use exam, MRI, CSF Protein, and other neurodiagnostic tests to assess.

16. Moderate Risk Children: Genotype examples
p.A5P / p.D232N / p.Y303C // p.A5P / p.D232N / p.T96A
9.7% nmol/hr/mg protein
30Kb deletion / p.R168C // p.R168C / p.I546T
7.1% nmol/hr/mg protein
c.-335G>A / p.P73L / p.I546T // g.30Kb deletion / p.R168C
9.8% nmol/hr/mg protein
p.L618S / p.D445A // p.L618S
8.3% nmol/hr/mg protein
p.A5P / p.D232N / p.Y303C // p.A5P / p.D232N / p.Y303C
8.9% nmol/hr/mg protein 16

17. What does our DNA data tell us?
All patients that were determined to have infantile Krabbe disease have two mutations, which would be considered to be pathogenic.
- This doesn’t mean this will always be the case
Some pathogenic mutations that are not obvious
examples: Y551S, T513M , Y287F, R380L
All high risk patients have two mutations (some are novel, some are known to be disease- causing)
Most moderate risk patients (12/18) have two mutations. Hard to predict if someone with two variants will be high or moderate risk
Most low risk patients only have one detected mutation

18. What constitutes a Diagnosis?
Clinical symptoms (or abnormal neurodiagnostic test results)
Low Enzyme activity
Elevated substrate
(currently unknown as not measured)
Two known disease causing mutations
In newborn screening, by definition, the child is asymptomatic, if low GALC activity, and one or two variants in DNA of unknown significance, need more information
Dx Positive

19. Managing Screen Positive Referrals Cross discipline effort is required
Involve treatment centers early – to get buy-in and determine steps to diagnose
Determine best mechanism for communicating a screen positive result! Varied communications lead to varied compliance with follow-up.
If possible, determine exactly how the patient will be evaluated, and steps to be taken to treatment.
Involve neurologists-not always linked to TCs
Involve transplant physicians
Engage payers / Public and Private