Krabbe DiseaseClinical Experience and

Long-term Management

Sphingolipids

Glucocerebroside

Farber disease

Ceramidase

Sphingosine

Fatty acid

-Galctosidase

Ceramide

Galactosylcerebroside

Galactosylceramide -galactosidase

Krabbe disease

Arylsulfatase AMetachromatic leukodystrophy

Sulfatide

CeramideSO4

Krabbe Disease

Galacotoceramide β-galactosidase deficiency Also called Globoid Cell Leukodystrophy Infantile form (85 – 90%): onset at 6 months

and death by 2 yearsExtreme 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

2006 New York State

Newborn Screening of Krabbe Disease Began

Referred infants: After NBS Screening

• Confirmatory Enzyme Analysis (Dr. David A. Wenger)Consult with Geneticist/ Child NeurologistDraw blood sample – e.g. HLA typing

• If enzyme test affirms Krabbe disease likely..ExamCSF proteinMRINerve 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

Referred infants - Risk categories

GALC ACTIVITY RISK CATEGORYnmol/hr/mg protein

0.0 0.15 High

0.16 0.29 Moderate

Eliminated low risk category Jan. 1, 2012

> 0.3 * No Risk

Courtesy of Dr. P. Duffner

• Note that infants found with 2 or more mutations and > 0.3 activity, will be categorized as at moderate risk.

CRITERIA FOR HCT REFERRAL

Consider Transplantation for scores > 4 PointsPoints

• Abnormal Neurologic Exam 2• Abnormal MRI 2• Abnormal LP (Increased Protein) 2• Abnormal NCV 1• Abnormal BAER 1• Abnormal VER 1• 30 KB Homozygous Deletion 4

8

New York State Newborn Screening for Krabbe Disease August 7, 2006 to May 31, 2012

1,556,172 Screened for low GALC ActivityThreshold activity ≤12% daily mean

High Throughput MS/MS

601 DNA sequencing started452 sequencing completed191 low activity polymorphisms

261→ Counseling and Venous Confirmation

25 mod. risk

12 high risk(4 KD*)

3H labeled - natural substrate0.3 - 0.5 ηmol/h/mg protein0.15 - 0.3 ηmol/h/mg protein

DriedBloodSpot

DriedBloodSpot

VenousBlood &Follow up

8 “healthy” up to 60 mos3 → HCT, 1 dead, 1 chronic hemolytic anemia 1 → refused HSCT

< 0.15 ηmol/h/mg protein

*4KD Predicted to have infantile formBased on genotype and neurodiagnostic testing

Annual Assessments

Center VisitsNeurologic Assessment

Neurologic Testing

(LP, MRI, BAER, VER, NCT)—high and moderate risk babies only

Cognitive Testing

Courtesy of Dr. P. Duffner

Outcomes Study

Phone call interviews: 4, 8, 12, 18, 24 months of age--Ages and Stages Questionnaire

--Wee FIM 0-3

--Warner IDEA FSEarly intervention referral as neededComparison with annual Bayley III

Courtesy of Dr. P. Duffner

Neurological Evaluation Neurodiagnostic

Year 1 Q Month Q 3 MonthsHigh Risk

Year 2 Q 3 Months Q 6 Months

Year 1 Q 3 Months AnnualMod Risk

Year 2 Q 3 Months Annual

Year 1 Q 6 Months Annual*Low Risk

Year 2 Q 6 Months Annual*

EVALUATION SCHEDULE

12

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.

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

4. g.30Kb deletion // p.A5P/ G360DfsX2 [TP]5.6% 0.12 nmol/hr/mg protein

High Risk Children/Asymptomatic

p.A5P / p.D232N / p.Y303C // p.A5P / p.D232N / p.Y303C6.1% 0.06 nmol/hr/mg protein

p.A5P / p.D232N / p.Y303C / p.I546T // p.D556X8.3% 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.

Moderate Risk Children: Genotype examples

p.A5P / p.D232N / p.Y303C // p.A5P / p.D232N / p.T96A9.7% 0.18 nmol/hr/mg protein

30Kb deletion / p.R168C // p.R168C / p.I546T7.1% 0.26 nmol/hr/mg protein

c.-335G>A / p.P73L / p.I546T // g.30Kb deletion / p.R168C 9.8% 0.29 nmol/hr/mg protein

p.L618S / p.D445A // p.L618S8.3% 0.24 nmol/hr/mg protein

p.A5P / p.D232N / p.Y303C // p.A5P / p.D232N / p.Y303C8.9% 0.28 nmol/hr/mg protein

What does our DNA data tell us?

1. 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

2. All high risk patients have two mutations (some are novel, some are known to be disease- causing)

3. Most moderate risk patients (12/18) have two mutations. Hard to predict if someone with two variants will be high or moderate risk

4. Most low risk patients only have one detected mutation

What constitutes a Diagnosis?

Diagnosis

Low Enzyme activity

Elevated substrate(currently unknown as not measured)

Two known disease causing mutations

Clinical symptoms (or abnormal neurodiagnostic test results)

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

• 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

Managing Screen Positive ReferralsCross discipline effort is required