Carrier screening for Krabbe disease in an isolated inbred community.

Infantile Krabbe disease (OMIM 245200) is a severe, fatal autosomal recessive neurodegenerative disorder that is relatively frequent in two Muslims villages within Jerusalem. After the characterization of the founder mutation, a population carrier screening for Krabbe disease became a component of the Israeli program for the detection and the prevention of birth defects. Between 2010 and 2018, 3366 individuals were tested and among them 247 carriers for Krabbe disease were identified (7.3%). Most of the 21 carrier couples identified that had pregnancies after being informed that they were at risk used preventive measures including termination of pregnancies of affected fetuses. During the study period, eight children affected with Krabbe disease were born in the villages, four to couples not detected though the program. Twenty years after the beginning of the carrier screening program, Krabbe disease remained relatively frequent in the villages. The establishment of a genetic clinic in the villages may allow to improve the carrier screening program while giving individual counseling for the risk to the other genetic diseases existing in the villages.

Hospitalization Burden and Incidence of Krabbe Disease.

OBJECTIVE: The purpose of our study was to understand the healthcare burden and incidence of Krabbe disease (Krabbe). METHODS: Retrospective analysis of Krabbe patients identified October 1, 2015 through December 31, 2020, ages birth through age 3, evaluated in two national databases. We estimated point prevalence and incidence from year 2016 data. RESULTS: We identified 98 unique Krabbe patients with 736 visits including 260 were inpatient admissions. Total healthcare charges were $51.5 million dollars. We determined a point prevalence of 34 68 Krabbe patients in 2016 ages 0 3 years. This estimates a birth incidence of ~1 in 310,000 live births. Significance: Krabbe disease patients had over $51 million in health care charges and hundreds of hospitalizations. Estimated prevalence and birth incidence is similar to rates observed from newborn screening. Our findings show the tremendous health impacts of Krabbe disease, and provide guidance for efforts in screening and treatment planning.

Genetic testing of leukodystrophies unraveling extensive heterogeneity in a large cohort and report of five common diseases and 38 novel variants.

This study evaluates the genetic spectrum of leukodystrophies and leukoencephalopathies in Iran. 152 children, aged from 1 day to 15 years, were genetically tested for leukodystrophies and leukoencephalopathies based on clinical and neuroradiological findings from 2016 to 2019. Patients with a suggestive specific leukodystrophy, e. g. metachromatic leukodystrophy, Canavan disease, Tay-Sachs disease were tested for mutations in single genes (108; 71%) while patients with less suggestive findings were evaluated by NGS. 108 of 152(71%) had MRI patterns and clinical findings suggestive of a known leukodystrophy. In total, 114(75%) affected individuals had (likely) pathogenic variants which included 38 novel variants. 35 different types of leukodystrophies and genetic leukoencephalopathies were identified. The more common identified disorders included metachromatic leukodystrophy (19 of 152; 13%), Canavan disease (12; 8%), Tay-Sachs disease (11; 7%), megalencephalic leukodystrophy with subcortical cysts (7; 5%), X-linked adrenoleukodystrophy (8; 5%), Pelizaeus-Merzbacher-like disease type 1 (8; 5%), Sandhoff disease (6; 4%), Krabbe disease (5; 3%), and vanishing white matter disease (4; 3%). Whole exome sequencing (WES) revealed 90% leukodystrophies and genetic leukoencephalopathies. The total diagnosis rate was 75%. This unique study presents a national genetic data of leukodystrophies; it may provide clues to the genetic pool of neighboring countries. Patients with clinical and neuroradiological evidence of a genetic leukoencephalopathy should undergo a genetic analysis to reach a definitive diagnosis. This will allow a diagnosis at earlier stages of the disease, reduce the burden of uncertainty and costs, and will provide the basis for genetic counseling and family planning.

Elevated Leukodystrophy Incidence Predicted From Genomics Databases.

BACKGROUND: Leukodystrophies are genetic diseases affecting the white matter and leading to early death. Our objective was to determine leukodystrophy incidence, using genomics sequencing databases allele frequencies of disease-causing variants. METHODS: From 49 genes, representing the standardly defined group of leukodystrophies, we identified potential disease-causing variants from publications in the Human Genetic Mutation Database and from predictions in the Genome Aggregation Database. Allele frequencies were estimated from Genome Aggregation Database. Allele frequencies for each gene were summed to generate a super allele frequency and we used the Hardy-Weinberg equation to calculate overall expected live birth incidence associated with the gene in question. RESULTS: We identified 4564 pathogenic variants for 25 discrete leukodystrophies. The largest effect was from GALC variants (Krabbe disease), which had a predicted incidence of one in 12,080 live births, 8.3 times higher than published estimates. The second most frequently predicted leukodystrophy was the RNA polymerase III-related disorders, which had an incidence of 1:26,160. Overall, we found a leukodystrophy incidence of 1 in 4733 live births, significantly higher than previous estimates. CONCLUSIONS: Our data are consistent with a significant underdiagnosis of leukodystrophy patients. An intriguing additional consideration is that there may be genetic modifiers that lead to weaker, absent, or adult-onset disease phenotypes.

Large-scale study of clinical and biochemical characteristics of Chinese patients diagnosed with Krabbe disease.

Krabbe disease (KD) is a rare disease caused by the deficiency of ß-galactocerebrosidase. This study investigated 22 unrelated Chinese patients, including their clinical presentations, plasma psychosine levels and ß-galactocerebrosidase gene mutations. We found the late-onset form of KD present in 82% of the patients in our study, which was more prevalent than in patients from other populations. Plasma psychosine levels were elevated in KD, which were correlated with the severity of clinical presentations. Sanger sequencing identified 8 novel mutations, including 7 missense mutations, p.H253Y, p.S259L, p.P318L, p.F350V, p.T428A, p.L530P, p.G586D, and 1 splicing mutation, c.1251+1G>A. Quantitative real-time polymerase chain reaction (PCR) and multiplex ligation-dependent probe amplification identified a novel exon 12 and 14 deletion, separately. Next generation sequencing, applied at the final step, revealed 2 missense mutant alleles missed using Sanger sequencing. The most common mutation in Chinese population is p.P154H, which accounts for 20.5% of alleles. Consistent with the higher prevalence of the late-onset form of KD, missense mutations predominated in our study, different with the common mutation types in Europe and Japan. This work was the first large-scale study of Chinese KD patients describing their clinical, biochemical and genetic characteristics, which furthered our understanding of this classical neurological lysosomal storage disease.

Death rates in the U.S. due to Krabbe disease and related leukodystrophy and lysosomal storage diseases.

Leukodystrophies (LD) and lysosomal storage disorders (LSD) have generated increased interest recently as targets for newborn screening programs. Accurate epidemiological benchmarks are needed in the U.S. Age-specific mortality rates were estimated for Krabbe disease (KD) and nine related disorders. U.S. mortality records with E75.2 cause of death code during 1999-2004 were collected from 11 open record states. All E75.2 deaths in the United States were distributed into specific disease type based on proportions observed in these states. Yearly population sizes were obtained from the CDC and averaged. Mortality rates (per million individuals per year) by age group for the specific diseases were (for <5 or ≥5 years): Pelizaeus-Merzbacher (0.037/0.033); sudanophilic leukodystrophy (SLD) (0.037/0.004); Canavan (0.037/0.011), Alexander (0.147/0.022); Krabbe (0.994/0.007); metachromatic leukodystrophy (0.331/0.135); Fabry (0.000/0.124); Gaucher (0.221/0.073); Niemann-Pick (NP) (0.442/0.088); multiple sulfatase (0.000/0.004). This is the first report of mortality rates for the LD/LSD diseases in the U.S. Approximated birth prevalence rate for the early infantile Krabbe phenotype (onset 0-6 months) was based on the <5 year old mortality rate of one early infantile case per 244,000 births, which matches the 1 in 250,000 observed in the NYS newborn screening program as of 2011. It should be noted however that the NYS calculation refers only to the early infantile phenotype and does not include the majority of babies identified in the program with low GALC and two mutations who have remained clinically normal. It is presumed that most, if not all, will develop later onset forms of the disease, but this is by no means certain.

Early infantile Krabbe disease: results of the World-Wide Krabbe Registry.

New York State began screening for Krabbe disease in 2006 to identify infants with Krabbe disease before symptom onset. Because neither galactocerebrosidase activity nor most genotypes reliably predict phenotype, the World Wide Registry was developed to determine whether other clinical/neurodiagnostic data could predict early infantile Krabbe disease in the newborn screening population. Data on disease course, galactocerebrosidase activity, DNA mutations, and initial neurodiagnostic studies in 67 symptomatic children with early infantile Krabbe disease were obtained from parent questionnaires and medical records. Initial signs included crying/irritability, cortical fisting, and poor head control. Galactocerebrosidase activity was uniformly low. Eight of 17 manifested novel mutations. Ninety-two percent (n = 25) exhibited elevated cerebrospinal fluid protein; 76% (n = 42) demonstrated abnormal magnetic resonance images; 67% (n = 15) exhibited abnormal computed tomography findings; 43% (n = 28) produced abnormal electroencephalogram findings; 100% (n = 5) demonstrated abnormal nerve conduction velocities; 83% (n = 6) produced abnormal brainstem evoked responses; and 50% (n = 6) exhibited abnormal visual evoked responses. One, 2, and 3 year survivals were 60%, 26%, and 14%, respectively. Although most symptomatic patients with the early infantile phenotype manifested abnormal cerebrospinal fluid protein, magnetic resonance imaging, brainstem evoked responses, and nerve conduction velocities, studies of affected children may be normal. Other biomarkers are needed to predict phenotype in the newborn screening population.

Krabbe leukodystrophy in a selected population with high rate of late onset forms: longer survival linked to c.121G>A (p.Gly41Ser) mutation.

Krabbe leukodystrophy (KD) is a neurodegenerative lysosomal disorder caused by mutations in the galactocerebrosidase (GALC) gene. Different clinical forms are described based on the age at onset. In reported series, the early infantile form (EIKD) accounts for more than 90% of the cases. The rarer late onset forms (LOKD) become manifest later than 6 months up to the adult age. We report clinical, imaging, mutational analysis and geographic data in a large cohort of individuals with Krabbe disease examined over a 30-year period. Retrospective analyses of disease onset and long-term follow-up were conducted in 26 KD patients. Molecular analysis was performed in 12 patients and their families. Nine cases had EIKD, and 17 LOKD, accounting for two thirds of our series. No correlation was found between enzymatic activity, onset age and disease progression. Despite common geographical origin, only in a few cases could parental consanguinity be proven. The p.Gly41Ser mutation was associated with longer survival. A wide spectrum of LOKD is found despite similar genotype. Although current knowledge about onset age, residual enzyme activity and molecular analysis still fail to allow the identification of patient candidates for treatment, this information is valuable for long-term outcome prediction and could lead to reconsideration of inclusion criteria for bone marrow transplant (BMT) or other future therapeutic approaches.

Krabbe disease: neurophysiologic studies and MRI correlations.

BACKGROUND: Krabbe disease (KD) is a rare hereditary leukodystrophy affecting children mostly in the first 6 months of life; later onset has been reported as well. OBJECTIVE: To review abnormalities in neurophysiologic studies in children with KD and determine if there is a correlation between these studies and disease severity as measured by MRI scans. METHODS: KD patients with at least one neurophysiologic study and one MRI scan at the authors' institution were reviewed. Relationships between KD type, neurophysiologic studies, and severity of disease as measured by MRI were explored. RESULTS: Data were available for 26 children: 20 with early infantile KD (EIKD) and 6 with late-onset KD (LOKD). Flash visual evoked potentials were abnormal in 53% of EIKD children, whereas none of the LOKD children had an abnormal study. Brainstem auditory evoked potentials were abnormal in 88% of EIKD and 40% of LOKD children. EEGs were abnormal in 65% of EIKD and 33% of LOKD children. Nerve conduction studies were abnormal in all children with EIKD and in 20% of LOKD children. Abnormal neurophysiologic studies correlated with more extensive disease as measured by MRI scans. CONCLUSIONS: Children with early infantile Krabbe disease and late-onset Krabbe disease have different patterns of abnormalities in neurophysiologic studies. These studies offer an objective means of assessing KD and correlate well with disease severity measured by MRI scans.

Brain-stem auditory and visual evoked potentials in children with Krabbe disease.

OBJECTIVE: There are few reports in the literature detailing brain-stem auditory and visual evoked potentials (BAEP and VEP) in children with Krabbe disease (KD). The purpose of this study was to provide a descriptive analysis of the BAEP and VEP findings in these children. METHODS: Charts of children with KD were reviewed. BAEP and VEP studies performed on these children were reviewed; findings in the early infantile and late onset KD (EIKD, LOKD, respectively) groups were also examined. Likelihood ratios (LR) for the neurophysiologic tests being abnormal in the various groups were also determined. RESULTS: BAEP abnormalities were seen in 15/17 (88%) children with EIKD and 2/5 (40%) children with LOKD, LR statistically significant. In the EIKD group, all 13 symptomatic children had an abnormal BAEP, whereas 2/4 (50%) of the pre-symptomatic children had similar findings, LR statistically significant. VEP abnormalities were noted in 8/15 (53%) children with EIKD and none of the children with LOKD, LR statistically significant. In the EIKD group, the 8/12 (67%) symptomatic children had an abnormal VEP, whereas none of the pre-symptomatic children did, LR statistically significant. Subgroup analyses of the LOKD subgroups did not yield significant findings. CONCLUSIONS: BAEP abnormalities are among the first objective indications of central nervous system disease in children with EIKD. VEP abnormalities occur later in the course of the illness. Both tests are less helpful in children with LOKD. SIGNIFICANCE: BAEP and VEP testing is helpful in objective evaluation of children with KD.

Allogeneic bone marrow transplantation for infantile globoid-cell leukodystrophy (Krabbe's disease).

A 4-month-old-girl affected by early expression of Krabbe's disease was treated with allogeneic bone marrow transplantation (BMT). The stem cell donor was her heterozygous HLA-identical mother. The central nervous system (CNS) involvement at diagnosis was evident, but minimal. After BMT the child presented a severe hypotonia and an acute tetraventricular hydrocephalus; she died 180 days after the BMT with progressive severe neurologic deterioration. Leukocyte galactocerebrosidase (GALC) activity was present at donor levels 20 days after BMT. Full donor chimerism was evident 18 days after BMT. This report confirms that in early onset "Krabbe's syndrome" if the diagnosis is delayed after the birth, the progression of the neurologic deterioration is not reversed by BMT. It is to be demonstrated if a very early hemopoietic stem cell transplantation during the first weeks of life, could be appropriate and efficacious.

Residual galactosylsphingosine (psychosine) beta-galactosidase activities and associated GALC mutations in late and very late onset Krabbe disease.

BACKGROUND: Krabbe disease (globoid-cell leukodystrophy; GLD) is caused by mutations in the GALC gene. Beta-galactocerebrosidase (GALC) is a specific beta-galactosidase which is defective in GLD. About 90% of GLD patients have an infantile course by fatal cerebral demyelination, but 10% have a later onset (LOGLD) of symptoms and survive for one or several decades. METHODS: Activities of GALC towards galactosylceramide (GC) and galactosylsphingosine (psychosine; PS) were determined in white blood cells and cultured fibroblasts derived from GLD patients and controls using tritium-labelled natural substrates. In the galactosylsphingosine (psychosine) beta-galactosidase (GALC-PS) assay, a thin layer chromatographic technique was used to separate enzymatically released radioactive galactose. RESULTS: Both galactosylceramide beta-galactosidase (GALC-GC) and GALC-PS activities were reduced by at least 85% of the normal in all but 2 of the 10 GLD patients studied. In particular, one 23-year-old severely demyelinated LOGLD patient was strongly deficient (11% of the normal) in GALC-GC but apparently normal for GALC-PS activity. This patient's GALC genotype was the 30-kb-deleted/502T allele combined with a wild-type allele in the 1637C background known to slightly reduce GALC-GC activity. Further, of six LOGLD patients, both of 62- and 63-year-old brothers had the deleted allele combined with an 809G>A mutated 1637C allele. The sibs had strongly reduced GALC-GC and GALC-PS activities but became clinically remarkable only in their 50s with a severe mental downhill course in one of them. CONCLUSIONS: A GALC genotype with one deleted and one polymorphic GALC activity-reducing allele can lead to enzymatic and clinical signs of LOGLD in the absence of marked GALC-PS deficiency. If an active PS hydrolysis in the fibroblasts of a LOGLD patient also reflected such hydrolysis in the brain, the psychosine hypothesis for GLD may need to be revised.

Krabbe disease--clinical profile.

OBJECTIVE: To study clinical features and investigations of children with Krabbe Disease (KD). DESIGN: Retrospective. SETTING: Genetic Clinic of a tertiary care teaching hospital. METHODS: Hospital records of patients with enzymatically confirmed KD were analyzed with respect to their clinical features and investigations including neuroimaging (CT-scan and/or MRI). Galactocerebrosidase (GALC) activity was estimated photometrically in the peripheral blood leukocytes. RESULTS: Nine children (age ranging from 2 1/2 months to 8 years) were studied, of which 5 had the classical infantile disease, 3 had late infantile form and one was diagnosed as juvenile KD. GALC levels in peripheral blood leukocytes were low or absent in all. Most of the children with infantile disease presented with neurodegeneration, seizures or fever. Optic atrophy was uncommon in our series (present only in a single case). Majority of the cases had elevated cerebrospinal fluid (CSF) protein levels and peripheral neuropathy on nerve conduction (NC) studies. Findings typical of KD were noted in 7 patients who underwent magnetic resonance imaging (MRI). The sole patient with juvenile disease presented with developmental delay and progressive spastic quadriparesis. CONCLUSION: Krabbe disease should be considered in the differential diagnosis of early infantile onset of neurodegeneration with seizures. Likewise, older children with progressive ataxia or spastic quadriparesis in whom the etiology remains obscure, must be investigated for Krabbe disease. MRI can be diagnostic in absence of availability of enzyme diagnosis.

Autosomal recessive diseases among Palestinian Arabs.

As a consequence of the high consanguinity rate among the Palestinian Arabs, many recessive disorders are present with a relatively high frequency. In a survey of 2000 different Palestinian Arab families who visited our genetic clinic, in 601 an autosomal recessive disease was diagnosed or strongly suspected. The distribution of these disorders was not uniform and some disorders, such as Krabbe disease, were found at high frequency in only a small part of the population. For some other disorders, a high prevalence was also reported among Palestinian Arabs living in other regions, for example, beta thalassaemia, Bardet-Biedl syndrome, Meckel syndrome, autosomal recessive congenital hydrocephalus, and recessive osteopetrosis. In addition, as another consequence of the high consanguinity rate, two different autosomal recessive diseases were diagnosed within the same sibship in 17 of the Palestinian Arab families.

Leukodystrophy incidence in Germany.

Through a survey of all departments of pediatrics, neurology and neuropathology in Germany, we calculated the incidence of all major forms of leukodystrophy. Only diagnoses based on specific biochemical tests in association with typical findings and/or neuroradiologically proven white matter involvement were accepted. In accordance with these strict criteria, 617 cases of leukodystrophy were found (incidence of all forms: app. 2.0/100,000). Minimal incidence was estimated at 0.8/100,000 for adrenoleukodystrophy/adrenomyeloneuropathy (ALD/AMN), 0.6/100,000 for metachromatic leukodystrophy (MLD), and 0.6/100,000 for Krabbe disease. Thus ALD/AMN is apparently underdiagnosed in Germany. A considerable proportion of leukodystrophies could not be classified in spite of adequate diagnostic procedures in experienced centers.

Krabbe disease in Israel.

Over a period of 15 years, 18 infants affected with Krabbe disease were diagnosed in Israel. None of the patients were Jews. Six were Druze from a large kindred in which a very high incidence of the disease was previously reported. The 12 other patients were Moslem Arabs; 7 were from two adjacent villages and most of them were found to be related, originating from a large kindred in which the incidence of the disease is 1/130 live births. Three other patients were from a third large kindred that also had a high incidence of Krabbe disease. Israel's population includes communities in which a high incidence of lysosomal diseases has been found. The incidence of these diseases in Israel may be reduced by delineating the populations at risk. With respect to Krabbe disease, as reported here, the tests for heterozygote detection are not sufficiently accurate for a screening of the populations at risk. Prevention is possible only by prenatal diagnosis in the families at risk.

Symptomatology of late onset Krabbe's leukodystrophy: the European experience.

The authors present a study of 50 patients with late onset Krabbe's leukodystrophy (LOKL), including 27 from a pooled European Series collected in 1987, and 23 published between 1906 and 1987. In Europe, the disease appears to be relatively frequent in Sicily and exceedingly rare in Sweden. Most cases started before the age of 5 years. The initial signs consisted mainly of progressive motor impairment, although, characteristically, visual failure was the initial manifestation in 25% of patients. Low nerve conduction velocities and a high protein content in the CSF were only present in 50%. There was no age-linked symptomatic predominance. The pace and length of the disease was very variable, but in one-third of the children before the age of 3 the course was remarkably rapid. There was no difference in the residual activity of galactosylceramide galactosidase in LOKL compared to the early infantile form.

Krabbe disease: increased incidence in a highly inbred community.

Krabbe disease (globoid cell leukodystrophy) was found with very high incidence (6/1,000 live births) in a large Druze kindred in Israel. The clinical data on 12 of the affected children demonstrated clinical variability even though these children are homozygous for the same mutation by descent from a common ancestor.

Clinical aspects of globoid cell and metachromatic leukodystrophies.

This paper describes the clinical, diagnostic, genetic and incidence aspects of globoid cell leukodystrophy and metachromatic leukodystrophy, the two least rare and most distinctive types among the leukodystrophies. It is based on experiences with 32 Swedish cases of globoid cell leukodystrophy (1953-1967) and 16 Swedish cases of metachromatic leukodystrophy (1956-1969). In both disorders it is now possible to make a correct diagnosis during life through various laboratory and biopsy procedures. An autosomal recessive inheritance is present in both of the disorders. The incidence of Krabbe's disease was found to be about 2:100,000 newborns in Sweden. The corresponding figure for metachromatic leukodystrophy is unknown at this time but is probably of about the same magnitude. This is the case in Northern Sweden.