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

Sphingolipids

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

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

Newborn Screening of Krabbe Disease Began 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 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

Referred infants - Risk categories GALC ACTIVITY RISK CATEGORY nmol/hr/mg protein 0.0 0.15 High 0.16 0.29 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

CRITERIA FOR HCT REFERRAL Consider Transplantation for scores > 4 Points Points 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 8

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 601 DNA sequencing started 452 sequencing completed 191 low activity polymorphisms Venous Blood & Follow up 261→ Counseling and Venous Confirmation 25 mod. risk 3H labeled - natural substrate 0.3 - 0.5 ηmol/h/mg protein 0.15 - 0.3 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

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

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

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

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.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.

Moderate Risk Children: Genotype examples p.A5P / p.D232N / p.Y303C // p.A5P / p.D232N / p.T96A 9.7% 0.18 nmol/hr/mg protein 30Kb deletion / p.R168C // p.R168C / p.I546T 7.1% 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.L618S 8.3% 0.24 nmol/hr/mg protein p.A5P / p.D232N / p.Y303C // p.A5P / p.D232N / p.Y303C 8.9% 0.28 nmol/hr/mg protein 16

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

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

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