Long-term neurodevelopmental outcomes of hematopoietic stem cell transplantation for late-infantile Krabbe disease

Krabbe disease is a rare neurodegenerative disorder caused by a deficiency in galactocerebrosidase. The only effective treatment is hematopoietic stem cell transplantation (HSCT). Approximately 85% of Krabbe disease cases are the infantile subtypes, among which ∼20% are late infantile. Prior studies have demonstrated that HSCT is effective for early-infantile patients (0-6 months of age) who undergo transplantation while asymptomatic, compared with those receiving transplants while symptomatic. However, no studies evaluated the efficacy of HSCT for late-infantile patients (6-36 months). In this prospective, longitudinal study, patients were evaluated at a single site according to a standardized protocol. Survival analysis was performed using the Kaplan-Meier method. Differences between groups were estimated using mixed regression models to account for within-person repeated measures. Nineteen late-infantile patients underwent HSCT (March 1997 to January 2020). Compared with untreated patients, transplant recipients had a longer survival probability and improved cognitive and language function. Gross and fine motor development were most affected, with variable results. Asymptomatic patients benefitted the most from transplantation, with normal to near-normal development in all domains and some gross motor delays. Among symptomatic patients, those with disease onset at >12 months of age had better cognitive outcomes than untreated patients. Those with disease onset at ≤12 months were comparable to untreated patients. We found that HSCT prolonged the lifespan and improved the functional abilities of late-infantile patients with Krabbe disease, particularly those who underwent transplantation before onset of symptoms. In addition, our findings support prior literature that reclassifies late-infantile Krabbe disease to be symptom onset at 12 to 36 months of age.

An Engineered Galactosylceramidase Construct Improves AAV Gene Therapy for Krabbe Disease in Twitcher Mice

Krabbe disease is an inherited neurodegenerative disease caused by mutations in the galactosylceramidase gene. In the infantile form, patients die before 3 years of age. Systemic adeno-associated virus serotype 9 (AAV9) gene therapy was recently shown to reverse the disease course in human patients in another lethal infantile neurodegenerative disease. To explore AAV9 therapy for Krabbe disease, we engineered a codon-optimized AAV9 galactosylceramidase vector. We further incorporated features to allow AAV9-derived galactosylceramidase to more efficiently cross the blood-brain barrier and be secreted from transduced cells. We tested the optimized vector by a single systemic injection in the twitcher mouse, an authentic Krabbe disease model. Untreated twitcher mice showed characteristic neuropathology and motion defects. They died prematurely with a median life span of 41 days. Intravenous injection in 2-day-old twitcher mice reduced central and peripheral neuropathology and significantly improved the gait pattern and body weight. Noticeably, the median life span was extended to 150 days. Intraperitoneal injection in 6- to 12-day-old twitcher mice also significantly improved the motor function, body weight, and median life span (to 104 days). Our results far exceed the ≤70 days median life span seen in all reported stand-alone systemic AAV therapies. Our study highlights the importance of vector engineering for Krabbe disease gene therapy. The engineered vector warrants further development.

A prospective natural history study of Krabbe disease in a patient cohort with onset between 6 months and 3 years of life

BACKGROUND

Krabbe disease is a rare neurodegenerative disorder caused by a deficiency in the lysosomal enzyme galactocerebrosidase. Patients with Krabbe disease present with a variable disease course depending on their age of onset. The purpose of this prospective cohort study was to characterize the natural progression of Krabbe disease in a large group of patients with disease onset between 6 and 36 months of life who were evaluated with a standardized protocol.

METHODS

All patients with Krabbe disease who had onset between 6 and 36 months of age and were prospectively evaluated between 2000 to 2017 were included. Standardized neurodevelopmental, physical, and neurological examinations were performed. Other assessments included neuroradiologic and neurophysiologic tests, enzyme level, cerebrospinal fluid analysis, and GALC pathogenic variants when available. Descriptive statistics were used for analysis. Survival curve was estimated using the Kaplan-Meier method.

RESULTS

Thirty-five patients (26 boys, 9 girls) with disease onset between 6 and 36 months of age were evaluated. Median age at symptom onset was 11.5 months, with a median delay of 3.5 months between onset of symptoms and diagnosis. Of the 32 symptomatic patients, 23 presented with initial signs or symptoms of disease between 6 and 12 months of life; nine presented after 12 months. The most common initial signs and symptoms were loss of acquired developmental milestones, irritability, abnormal gait, motor delay, and abnormal muscle tone. The most common magnetic resonance imaging abnormality was increased T2 signal in the periventricular white matter. Nerve conduction velocity results were abnormal for 21 of 24 patients. Patients with onset after 12 months had less peripheral nerve involvement and slower disease progression. Abnormal cerebrospinal fluid protein levels were obtained for 13 of 16 symptomatic children. Protein levels were normal in all asymptomatic children.

CONCLUSIONS

Based on our findings, we propose reclassifying the group of patients with onset ≤12 months as infantile and the > 12 month group as late-infantile. Patients with onset > 12 months are more likely to benefit from hematopoietic stem cell transplantation. The proposed change in classifications will allow physicians to improve their ability to recognize and diagnose patients and more precisely assess potential treatment effects after transplantation.

Mesenchymal Stem Cells Yield Transient Improvements in Motor Function in an Infant Rhesus Macaque with Severe Early-Onset Krabbe Disease

Krabbe disease, or globoid cell leukodystrophy, is a rare disorder caused by deficient galactosylceramidase activity and loss of myelin-forming oligodendrocytes, resulting in progressive demyelination and severely impaired motor function. Disease symptoms in humans appear within 3-6 months of age (early infantile) and manifest as marked irritability, spasticity, and seizures. The disease is often fatal by the second year of life, with few effective treatment options. Herein we evaluated the therapeutic potential of mesenchymal stem cells (MSCs) administered intracranially to a 1-month-old rhesus macaque diagnosed with severe early-onset Krabbe disease that displayed neurologic and behavioral symptoms similar to those of human patients. The infant was subjected to physical and neurological behavior examinations and nerve conduction velocity tests to assess efficacy, and outcomes were compared with age-matched normal infants and Krabbe-affected rhesus monkeys with late-onset disease. Changes in major blood lymphocyte populations were also monitored to assess host immune cell responses. MSC administration resulted in transient improvements in coordination, ambulation, cognition, and large motor skills, which correlated with increased peripheral nerve conduction velocities and decreased latencies. Improvements also corresponded to transient increases in peripheral blood lymphocyte counts, but secondary challenge failed to elicit allo-antibody production. Nevertheless, white cell and neutrophil counts showed dramatic increases, and CD20+ B cell counts underwent a precipitous decline at late stages of disease progression. Correlative data linking MSC administration to transient improvements in motor function suggest that MSCs should be evaluated further as an experimental therapy for rare neurodegenerative diseases. Stem Cells Translational Medicine 2017;6:99-109.

Pilot study of newborn screening for six lysosomal storage diseases using Tandem Mass Spectrometry

BACKGROUND

There is current expansion of newborn screening (NBS) programs to include lysosomal storage disorders because of the availability of treatments that produce an optimal clinical outcome when started early in life.

OBJECTIVE

To evaluate the performance of a multiplex-tandem mass spectrometry (MS/MS) enzymatic activity assay of 6 lysosomal enzymes in a NBS laboratory for the identification of newborns at risk for developing Pompe, Mucopolysaccharidosis-I (MPS-I), Fabry, Gaucher, Niemann Pick-A/B, and Krabbe diseases.

METHODS AND RESULTS

Enzyme activities (acid α-glucosidase (GAA), galactocerebrosidase (GALC), glucocerebrosidase (GBA), α-galactosidase A (GLA), α-iduronidase (IDUA) and sphingomyeline phosphodiesterase-1 (SMPD-1)) were measured on ~43,000 de-identified dried blood spot (DBS) punches, and screen positive samples were submitted for DNA sequencing to obtain genotype confirmation of disease risk. The 6-plex assay was efficiently performed in the Washington state NBS laboratory by a single laboratory technician at the bench using a single MS/MS instrument. The number of screen positive samples per 100,000 newborns were as follows: GAA (4.5), IDUA (13.6), GLA (18.2), SMPD1 (11.4), GBA (6.8), and GALC (25.0).

DISCUSSION

A 6-plex MS/MS assay for 6 lysosomal enzymes can be successfully performed in a NBS laboratory. The analytical ranges (enzyme-dependent assay response for the quality control HIGH sample divided by that for all enzyme-independent processes) for the 6-enzymes with the MS/MS is 5- to 15-fold higher than comparable fluorimetric assays using 4-methylumbelliferyl substrates. The rate of screen positive detection is consistently lower for the MS/MS assay compared to the fluorimetric assay using a digital microfluidics platform.

Compound Galactosylceramidase Gene (GALC) Heterozygosity in a Boy with Infantile Krabbe Disease (KD)

Krabbe disease (KD) (globoid cell leukodystrophy) is a degenerative, lysosomal storage disease, caused by a severe loss of galactocerebrosidase (GALC) enzymatic activity. The inheritance is autosomal recessive. KD affects the white matter of the central and peripheral nervous systems. We present a 3 year old boy in whom the disease had an 'infantile' or 'classic' presentation, with spasticity, irritability, and developmental delay. In addition the boy showed progressive severe motor and mental deterioration, difficulties in swallowing and decerebration. Molecular analysis revealed that the child is a compound heterozygote: p.Asp187Val (c.560A>T) and p.Ile250Thr (c.749T>C). The father was the carrier of p.Asp187Val (c.560A>T), while the mother was the carrier of the p.Ile250Thr (c.749T>C) in exon 6 of the GALC gene. The clinical course in this compound heterozygote is severe and the patient passed away at the age of 3 years. Genotype-phenotype relations are discussed in this Macedonian patient with KD.

Insights into the Pathogenesis and Treatment of Krabbe Disease

Krabbe disease (globoid cell leukodystrophy, GLD) is an inherited disease caused by a deficiency in the lysosomal enzyme galactocerebrosidase (GALC). The major galactosylated lipid degraded by GALC is galactosylceramide. However, GALC is also responsible for the degradation of galactosylsphingosine (psychosine), a highly cytotoxic glycolipid. It has been hypothesized that GALC-deficiency leads to psychosine accumulation that preferentially kills oligodendrocytes in the central nervous system and Schwann cells in the peripheral nervous system. Krabbe disease has traditionally been considered a white matter disease characterized by the loss and disorganization of myelin, infiltration of multinucleated monocytes/macrophages (globoid cells) and lymphocytes, and dysregulation of pro-inflammatory cytokines and chemokines. However, new studies have revealed unexpected neuronal deficiencies. Infantile Krabbe disease is believed to be the most common and aggressive form. However, juvenile and adult onset forms have been described. Children affected with infantile Krabbe disease present with motor dysfunction, cognitive decline, intractable seizures, and premature death between two to five years of age. Murine, canine, and primate models of GALC deficiency have been described and have played an important role in our understanding of this invariably fatal disease. Although there is no cure for Krabbe disease, hematopoietic stem cell transplantation can slow the progression of disease. Recent pre-clinical data indicate that simulataneously targeting multiple pathogenic mechanisms greatly increases efficacy in the murine model of Krabbe disease. A better understanding of the underlying pathogenesis will identify new therapeutic targets that may further increase efficacy.

History, genetic, and recent advances on Krabbe disease

Krabbe disease or globoid cell leukodystrophy is one of the classic genetic lysosomal storage diseases with autosomal recessive inheritance that affects both central and peripheral nervous systems in several species including humans, rhesus macaques, dogs, mice, and sheep. Since its identification in 1916, lots of scientific investigations were made to define the cause, to evaluate the molecular mechanisms of the damage and to develop more efficient therapies inducing clinical benefit and ameliorating the patients' quality of life. This manuscript gives a historical overview and summarizes the new recent findings about Krabbe disease. Human symptoms and phenotypes, gene encoding for β-galactocerebrosidase and encoded protein were described. Indications about the classical mutations were reported and some specific mutations in restricted geographical area, like the north of Catania City (Italy), were added. Briefly, here we present a mix of past and present investigations on Krabbe disease in order to update the knowledge on its genetic history and molecular mechanisms and to move new scientific investigations.

History, genetic, and recent advances on Krabbe disease

Krabbe disease or globoid cell leukodystrophy is one of the classic genetic lysosomal storage diseases with autosomal recessive inheritance that affects both central and peripheral nervous systems in several species including humans, rhesus macaques, dogs, mice, and sheep. Since its identification in 1916, lots of scientific investigations were made to define the cause, to evaluate the molecular mechanisms of the damage and to develop more efficient therapies inducing clinical benefit and ameliorating the patients' quality of life. This manuscript gives a historical overview and summarizes the new recent findings about Krabbe disease. Human symptoms and phenotypes, gene encoding for β-galactocerebrosidase and encoded protein were described. Indications about the classical mutations were reported and some specific mutations in restricted geographical area, like the north of Catania City (Italy), were added. Briefly, here we present a mix of past and present investigations on Krabbe disease in order to update the knowledge on its genetic history and molecular mechanisms and to move new scientific investigations.

Early axonal loss accompanied by impaired endocytosis, abnormal axonal transport, and decreased microtubule stability occur in the model of Krabbe's disease

In Krabbe's disease (KD), a leukodystrophy caused by β-galactosylceramidase deficiency, demyelination and a myelin-independent axonopathy contributes to the severe neuropathology. Beyond axonopathy, we show that in Twitcher mice, a model of KD, a decreased number of axons both in the PNS and in the CNS, and of neurons in dorsal root ganglia (DRG), occurred before the onset of demyelination. Despite the early axonal loss, and although in vitro Twitcher neurites degenerated over time, Twitcher DRG neurons displayed an initial neurite overgrowth and, following sciatic nerve injury, Twitcher axons were regeneration-competent, at a time point where axonopathy was already ongoing. Psychosine, the toxic substrate that accumulates in KD, induced lipid raft clustering. At the mechanistic level, TrkA recruitment to lipid rafts was dysregulated in Twitcher neurons, and defective activation of the ERK1/2 and AKT pathways was identified. Besides defective recruitment of signaling molecules to lipid rafts, the early steps of endocytosis and the transport of endocytic and synaptic vesicles were impaired in Twitcher DRG neurons. Defects in axonal transport, specifically in the retrograde component, correlated with decreased levels of dynein, abnormal levels of post-translational tubulin modifications and decreased microtubule stability. The identification of the axonal defects that precede demyelination in KD, together with the finding that Twitcher axons are regeneration-competent when axonopathy is already installed, opens new windows of action to effectively correct the neuropathology that characterizes this disorder.

Neuronal inclusions of α-synuclein contribute to the pathogenesis of Krabbe disease

Demyelination is a major contributor to the general decay of neural functions in children with Krabbe disease. However, recent reports have indicated a significant involvement of neurons and axons in the neuropathology of the disease. In this study, we have investigated the nature of cellular inclusions in the Krabbe brain. Brain samples from the twitcher mouse model for Krabbe disease and from patients affected with the infantile and late-onset forms of the disease were examined for the presence of neuronal inclusions. Our experiments demonstrated the presence of cytoplasmic aggregates of thioflavin-S-reactive material in both human and murine mutant brains. Most of these inclusions were associated with neurons. A few inclusions were detected to be associated with microglia and none were associated with astrocytes or oligodendrocytes. Thioflavin-S-reactive inclusions increased in abundance, paralleling the development of neurological symptoms, and distributed throughout the twitcher brain in areas of major involvement in cognition and motor functions. Electron microscopy confirmed the presence of aggregates of stereotypic β-sheet folded proteinaceous material. Immunochemical analyses identified the presence of aggregated forms of α-synuclein and ubiquitin, proteins involved in the formation of Lewy bodies in Parkinson's disease and other neurodegenerative conditions. In vitro assays demonstrated that psychosine, the neurotoxic sphingolipid accumulated in Krabbe disease, accelerated the fibrillization of α-synuclein. This study demonstrates the occurrence of neuronal deposits of fibrillized proteins including α-synuclein, identifying Krabbe disease as a new α-synucleinopathy.

Axonopathy is a compounding factor in the pathogenesis of Krabbe disease

Loss-of-function of the lysosomal enzyme galactosyl-ceramidase causes the accumulation of the lipid raft-associated sphingolipid psychosine, the disruption of postnatal myelination, neurodegeneration and early death in most cases of infantile Krabbe disease. This work presents a first study towards understanding the progression of axonal defects in this disease using the Twitcher mutant mouse. Axonal swellings were detected in axons within the mutant spinal cord as early as 1 week after birth. As the disease progressed, more axonopathic profiles were found in other regions of the nervous system, including peripheral nerves and various brain areas. Isolated mutant neurons recapitulated axonal and neuronal defects in the absence of mutant myelinating glia, suggesting an autonomous neuronal defect. Psychosine was sufficient to induce axonal defects and cell death in cultures of acutely isolated neurons. Interestingly, axonopathy in young Twitcher mice occurred in the absence of demyelination and of neuronal apoptosis. Neuronal damage occurred at later stages, when mutant mice were moribund and demyelinated. Altogether, these findings suggest a progressive dying-back neuronal dysfunction in Twitcher mutants.

Severe graft versus host disease in a patient with globoid cell leukodystrophy following umbilical cord blood transplantation: resemblance to the twitcher mouse model

Bone marrow transplantation (BMT) is currently the treatment of choice for patients with globoid cell leukodystrophy (GLD), particularly in the early phases of the disease. Elevated interleukin (IL)-6 levels in the central nervous system of the twitcher mouse, an animal model for GLD, have been held responsible for severe graft versus host disease (GVHD), and IL-6 knock-out mice have shown lower incidence of GVHD after BMT. Here we report an eight-year-old girl with late-onset advanced stage of GLD who developed severe GVHD and died following unrelated 5/6 matched cord blood transplantation. Serum IL-6 levels pre-BMT and at day +38 were elevated (20 pg/ml and 15 pg/ml, respectively). This observation may support the findings in twitcher mice suggesting a possible role for IL-6 in the pathogenesis of GVHD in transplanted patients with GLD.

Effects of irradiation on the postnatal development of the brain in a genetic mouse model of globoid cell leukodystrophy

Irradiation is one way to condition Twitcher mice--a natural model of globoid cell leukodystrophy (GLD)--prior to receive bone marrow transplantation (BMT). BMT showed to delay but not to completely prevent GLD disease in treated mutants. The reasons why BMT is not completely preventive in Twitchers are unclear but we speculate that irradiation might contribute to worsen the neurological impairments generated by the disease by altering postnatal neurogenesis. To test this hypothesis, we examined proliferation, migration and differentiation of neural precursors in neurogenic areas of the Twitcher brain after exposure of 5 day-old mutant pups to 620 rad, a non-lethal dose that leads to 80-90% of bone-marrow engraftment in classic BMT. Twitchers showed to be sensitive to irradiation, leading to a severe retardation of body growth of irradiated mutants. Irradiated Twitchers had reduced proliferation of neural precursors and increased astrogliosis and microgliosis, with reduced numbers of migratory neuroblasts and significantly less brain myelination. These effects were accompanied by caspase-3 activation and appeared largely irreversible in the lifespan of the Twitcher. Our work confirms that exposure of the neonatal brain to irradiation conditions such as those performed prior to BMT, can lead to long-lasting alterations of postnatal neurogenesis and myelination, which might contribute to worsen the progression of disease in these myelin mutants and to reduce the success of BMT.

Quantitative Analysis of Diffusion Tensor Imaging Data in Serial Assessment of Krabbe Disease

Krabbe disease is a rare autosomal recessive pediatric white matter (WM) disorder that is due to deficiency of a specific enzyme, beta-galactocerebrosidase. This report reviews our experience with use of diffusion tensor imaging (DTI) in serial assessment of WM changes in Krabbe disease following stem cell transplantation. DTI appears to be a sensitive means to monitor effects of stem cell transplantation on WM development in Krabbe disease. The group of early transplantation infants was clearly distinguishable from the group of late transplantation infants based on anisotropy measurements. Good correlation also was seen between neurodevelopmental scores and anisotropy measurements. The work described here in Krabbe disease may serve as a model for application of DTI to other therapies in various WM disorders such as multiple sclerosis and dysmyelinating disorders of childhood.

Myelin deterioration in Twitcher mice: motor evoked potentials and magnetic resonance imaging as in vivo monitoring tools

We have used magnetic resonance imaging (MRI) and motor evoked potentials (MEPs) for monitoring disease progression within the CNS of the Twitcher mouse, the murine model for globoid cell leukodystrophy (GLD). GLD is a lysosomal storage disorder, resulting from galactocerebrosidase deficiency, causing central and peripheral myelin impairment, leading to death, usually during early infancy. Neuroradiological, electrophysiological, and pathological parameters of myelin maturation were evaluated in Twitcher mice between postnatal days 20 and 45. Healthy controls showed a gradual-appearance MRI T2-weighted hypointensity of the corpus callosum (CC) starting at about P30 and ending at about P37, whereas MRI of age-matched Twitcher mice showed a complete loss of the CC-related MRI signal. MEPs allowed the functional assessment of myelin maturation within corticospinal motor pathways and showed a progressive deterioration of MEPs in Twitcher mice with increased central conduction time (CCT; 5.12 +/- 0.49 msec at P27 to 6.45 +/- 1.96 msec at P32), whereas physiological CCT shortening was found in healthy controls (3.01 +/- 0.81 msec at P27 to 2.5 +/- 0.27 msec at P32). These findings were not paralleled by traditional histological stainings. Optical observation of Bielchowsky and Luxol fast blue-PAS stainings showed mild axonal/myelin deterioration of the Twitcher brain within this time frame. Our results demonstrate that serial MRI and MEP readings are sensitive evaluation tools for in vivo monitoring of dysmyelination in Twitcher mice and underscore their potential use for longitudinal evaluation of the therapeutic impact of gene and cell therapies on these animals.

Krabbe disease--a case report

Krabbe disease is an extremely rare condition with an incidence of 1 in 1,00,000 live births. It is caused by deficient activity of the Iysosomal hydrolase galactosylceramide beta-galactosidase. A 6 years old male weighing 12 kg, was brought to Rajah Muthiah Medical College and Hospital with complaints of convulsions. The full-term child was delivered by lower segment caesarean section to second-degree consanguineous parents. The baby cried immediately after birth. The child attained normal milestones till two years of age. Thereafter he lost his attained milestones. The child had dysmorphic face with features like anti-Mongoloid eyes and teeth anomaly. Skin was lax all over the body especially over the face and was bruised. Respiratory distress and upward gaze were present. Bilateral crepitations were heard. Pupils were dilated and sluggishly reacted to light.

Insulin-like growth factor-1 provides protection against psychosine-induced apoptosis in cultured mouse oligodendrocyte progenitor cells using primarily the PI3K/Akt pathway

Psychosine (galactosylsphingosine) is a toxic metabolite that accumulates in globoid cell leukodystrophy (GLD) due to the deficiency of galactocerebrosidase (GALC) activity. This results in subsequent programmed cell death of oligodendrocytes and demyelination in human patients and animal models. We investigated the potential role of insulin-like growth factor-1 (IGF-1) in modifying the apoptotic effect of psychosine in cultured mouse oligodendrocyte progenitor cells (OLP-II). We show that psychosine inhibits the phosphorylation of Akt and Erk1/Erk2 (Erk1/2), which are the main anti-apoptotic pathways of the IGF-1 receptor (IGF-1R). Although IGF-1 sustained phosphorylation of both of these pathways, it provided maximum protection to OLP-II cells from psychosine-induced cell death in a PI3K/Akt-dependent manner. The effects of IGF-1 were dose-dependent and resulted in increased IGF-1R autophosphorylation levels. Although relatively high concentrations of IGF-1 also resulted in the activation of the insulin receptor (IR), its effect was more significant on the IGF-1R.

Serial electrophysiologic studies in rhesus monkeys with Krabbe disease

Krabbe disease is a progressive leukodystrophy that results in demyelination in the central and peripheral nervous systems in humans. It has been described in a number of mammalian species including the rhesus monkey. We performed serial nerve conduction studies beginning within the first 2 months of life in four homozygous, two heterozygous, and two normal rhesus monkeys (Macaca mulatta) to characterize the peripheral neuropathy. Mean conduction velocities of the median, ulnar, and tibial nerves were significantly slower in the affected than unaffected monkeys at all ages (P < 0.0001). The conduction velocity differences became more apparent between the affected and unaffected as the monkeys aged. When compared to the unaffected monkeys, the serial conduction velocities suggested occurrence of dysmyelination followed by demyelination in the affected monkeys. These observations provide further insight into the disease process and suggest an early window of opportunity for treating Krabbe disease.

Myelin-associated glycoprotein is altered in a familial late-onset orthochromatic leukodystrophy

Adult-onset dominant leukodystrophies are a heterogeneous group of rare disorders, whose etiology, pathogenesis and molecular background are still unknown. We report the neuropathological and biochemical investigations of the brains and their myelin proteins components in 2 members of an Italian family affected by an adult-onset autosomal dominant leukoencephalopathy. Clinical signs included spastic paraparesis, pseudobulbar syndrome, action tremor of head and hands, and moderate memory impairment. No mental deterioration or neuropathy was present. Onset was subacute (range 42-53 years) and progression spanned 4 to 7 years. The neuropathological phenotype overlapped that of orthochromatic leukodystrophies. The biochemical analysis revealed an abnormal myelin-associated glycoprotein (MAG); the defect was localized at the C-terminal domain of the L-MAG isoform, resulting in a protein approximately 5 kDa shorter than the normal counterpart. No mutation in the MAG gene-coding regions was uncovered, and linkage analysis formally excluded the entire MAG locus. We show that the identified MAG protein alteration is probably due to an abnormal post-translational event. Considering MAG function in the maintenance of myelin, the abnormal protein may have a role in the pathogenesis of this disease. This is the first report of a possible pathogenetic role of MAG in a hereditary disease affecting the central white matter.

Transplantation of umbilical-cord blood in babies with infantile Krabbe's disease

BACKGROUND

Infantile Krabbe's disease produces progressive neurologic deterioration and death in early childhood. We hypothesized that transplantation of umbilical-cord blood from unrelated donors before the development of symptoms would favorably alter the natural history of the disease among newborns in whom the disease was diagnosed because of a family history. We compared the outcomes among these newborns with the outcomes among infants who underwent transplantation after the development of symptoms and with the outcomes in an untreated cohort of affected children.

METHODS

Eleven asymptomatic newborns (age range, 12 to 44 days) and 14 symptomatic infants (age range, 142 to 352 days) with infantile Krabbe's disease underwent transplantation of umbilical-cord blood from unrelated donors after myeloablative chemotherapy. Engraftment, survival, and neurodevelopmental function were evaluated longitudinally for four months to six years.

RESULTS

The rates of donor-cell engraftment and survival were 100 percent and 100 percent, respectively, among the asymptomatic newborns (median follow-up, 3.0 years) and 100 percent and 43 percent, respectively, among the symptomatic infants (median follow-up, 3.4 years). Surviving patients showed durable engraftment of donor-derived hematopoietic cells with restoration of normal blood galactocerebrosidase levels. Infants who underwent transplantation before the development of symptoms showed progressive central myelination and continued gains in developmental skills, and most had age-appropriate cognitive function and receptive language skills, but a few had mild-to-moderate delays in expressive language and mild-to-severe delays in gross motor function. Children who underwent transplantation after the onset of symptoms had minimal neurologic improvement.

CONCLUSIONS

Transplantation of umbilical-cord blood from unrelated donors in newborns with infantile Krabbe's disease favorably altered the natural history of the disease. Transplantation in babies after symptoms had developed did not result in substantive neurologic improvement.

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.

Comparative Clinico-Pathological Study of Saposin-A-Deficient (SAP-A−/−) and Twitcher Mice

The Twitcher mouse (twi/twi) has been widely used as an animal model of globoid cell leukodystrophy (GLD; Krabbe disease), a hereditary leukodystrophy due to genetic galactosylceramidase deficiency. Recently, we generated a new mouse model of late-onset, chronic GLD (SAP-A-/- mice) by introducing a mutation (C106F) in the saposin A domain of the sphingolipid activator protein gene. Comparative study of SAP-A-/- and twi/twi mice revealed delay in the onset of neurological symptoms in SAP-A-/- mice (90 days vs 20 to 25 days), milder symptoms, and prolonged average survival (134.4 +/- 29.1 days vs 47.5 +/- 3.9 days). However, in both, the earliest sites of demyelination and macrophage infiltration were in regions of the 8th nerve and the spinal tract of the 5th nerve and spinal-cord, where macrophages could be detected as early as day 30 in asymptomatic SAP-A-/- mice. Furthermore, spacio-temporal pattern of demyelination/macrophage infiltration and the extent of neuropathology at the terminal stage are closely similar in both. These results suggest that peripheral macrophages are readily accessible in these sites and participate in the demyelinating process in the central nervous system.

Psychosine-induced apoptosis in a mouse oligodendrocyte progenitor cell line is mediated by caspase activation

Globoid cell leukodystrophy (GLD) is an inherited neurological disorder caused by the deficiency of galactocerebrosidase (GALC) activity resulting in cell death of oligodendrocytes and subsequent demyelination. The death of oligodendrocytes is accompanied by accumulation of psychosine, which is also a substrate for the GALC enzyme. In this report, we investigated the mechanism of the toxic effect of psychosine in a mouse-derived oligodendrocyte progenitor cell line (OLP-II), a precursor to the cell type most affected in GLD. Psychosine caused cytotoxicity in a dose-dependent manner. Lower concentration of psychosine (5 microM) did not significantly reduce OLP-II cell numbers. However, 50 microM psychosine induced up to 45% cell death. These results were confirmed by the Tunel assay, which is a hallmark for the detection of apoptosis. Moreover, psychosine treatment resulted in the activation/cleavage of initiator caspase-8 and -9, and effector caspase-3. These results support a role for psychosine in OLP-II cell death via an apoptotic mechanism, and suggest the involvement of caspases.

Are animal models useful for understanding the pathophysiology of lysosomal storage disease?

Spontaneously occurring genetic lysosomal storage diseases are as rare in other mammalian species as in man. However, the advent of gene targeting technology has revolutionized the state of animal models of genetic diseases. Nearly all lysosomal storage diseases known in man have been duplicated in the mouse. The technology now allows, not only complete inactivation of endogenous genes, but also the introduction of essentially any type of mutation. These animal models can overcome many of the limitations inherent in studies of human patients--rarity of the disease, extremely complex genetic background and logistical and ethical constraints in the design and execution of experiments with human subjects. For example, genetic manipulations of germ cells or cross-breeding experiments between two mutants are readily feasible with animal models. Two major areas of the utility of animal models are the clarification of the pathophysiology/pathogenetic mechanism of disease and the exploration of therapeutic approaches. Examples of experiments using animal models of lysosomal storage disease are presented, primarily from studies undertaken in our own laboratory.

CONCLUSION

Animal models have proved invaluable in extending our knowledge of the lysosomal storage diseases and exploring potential therapies.

Adult onset Krabbe disease may mimic motor neurone disease

Krabbe's disease (galactocerebrosidase deficiency) rarely presents in adults, usually with predominantly upper motor neurone clinical features. We report a case in whom the clinical features were similar to motor neurone disease. Nerve conduction studies and neuroimaging were important in leading to the correct diagnosis. Differences in adult-onset presentations are described.

Sphingolipid profile in the CNS of the twitcher (globoid cell leukodystrophy) mouse: a lipidomics approach

Globoid cell leukodystrophy (Krabbe disease) is caused by mutations in galactosylceramidase, a lysosomal enzyme that acts to digest galactosylceramide, a glycolipid concentrated in myelin, and psychosine (galactosylsphingosine). Globoid cell leukodystrophy has been identified in many species including humans and twitcher mice. Several studies on human tissue have examined the lipid profile in this disease by gas, liquid or thin layer chromatography. Electrospray ionization tandem mass spectrometry combined with reverse phase HPLC has become a powerful alternative strategy, used here to compare the sphingolipid profile of pons/medulla tissue from twitcher mice with control tissue. In this lipidomics LC-MS approach, we scanned for precursors of m/z 264 to obtain a semi-quantitative profile of ceramides and galactosylceramides. Sphingosine-1-phosphate, C18:0 ceramide, C22:0 ceramide and C24:0 ceramide levels were reduced in the pons/medulla of twitcher mice compared to levels in control mice at 31 and 35-37 days of age. The levels of C22:0 and C24:0 galactosylceramide were similar between twitcher and control specimens and there was a trend toward reduced levels of C24:1 galactosylceramide and C24:1 hydroxy-galactosylceramide in twitcher specimens. Psychosine, C 16:0 ceramide and C 18:0 galactosylceramide levels were increased in the CNS of twitcher mice compared to levels in control mice. These data indicate that there is a trend toward decreased levels of long chain fatty acids and increased levels of shorter chain fatty acids in galactosylceramides and ceramides from twitcher mice compared with control mice, and such changes may be due to demyelination characteristic of acute pathology.

Early peripheral nervous system manifestations of infantile Krabbe disease

Early infantile Krabbe disease is relatively frequent in the Muslim-Arab population in Israel. It can be easily diagnosed when it presents with the classic clinical picture characterized by central nervous system manifestations of spasticity, irritability, motor regression and seizures associated with a positive family history. We studied eight children diagnosed with Krabbe disease. In two of these children (25%), peripheral neuropathy was the single initial symptom and the only neurologic finding noted for a period of months. In these patients, diagnosis of Krabbe's disease was delayed and established only 9-11 months after the initial symptoms. In two other children with "classical picture" Krabbe disease, areflexia was noted on admission. The occurrence of peripheral neuropathy as an initial symptom in early infantile Krabbe disease may be underestimated. Krabbe disease should be considered in the differential diagnosis of early infantile peripheral neuropathy. Early diagnosis of affected children might be important for genetic counseling for families at risk.

Delayed clinical and pathological signs in twitcher (globoid cell leukodystrophy) mice on a C57BL/6 x CAST/Ei background

Modifier genes may account for the phenotypic variability observed in the late-onset forms of globoid cell leukodystrophy (GCL) in humans. In order to begin a search for modifier genes, the effect of genetic background on the clinical and pathological manifestations of GCL was investigated in twitcher mice. Twitcher mice on a C57BL/6 x CAST/Ei background had an increased life span (61.4 +/- 2.5 vs 37.0 +/- 0.6 days), a delayed onset of tremor (24 vs 21 days), and a delayed decline in walking ability compared to C57BL/6 twitcher mice. Pathologically, C57BL/6 x CAST/Ei twitcher mice had fewer lectin-positive globoid cells, less gliosis, and a greater preservation of myelin compared to C57BL/6 twitcher mice under moribund conditions. Similar concentrations of psychosine, the toxic species that accumulates in GCL, were measured by tandem mass spectrometry between moribund C57BL/6 twitcher mice (286.5 pmol/mg protein), 40-day C57BL/6 x CAST/Ei twitcher mice (276.5 pmol/mg), and moribund C57BL/6 x CAST/Ei twitcher mice (247.0 pmol/mg), suggesting that the milder phenotype in CAST/Ei x C57BL/6 twitcher mice did not correlate with less psychosine. In summary, the introduction of modifier genes from the wild, inbred CAST/Ei strain had a phenotypic effect resulting in a significantly slower disease course.

Sphingolipids involved in the induction of multinuclear cell formation

In this review, we focus on sphingolipids as potential regulators of the induction of multinuclear cell formation through the inhibition of cytokinesis. A sphingolipid, psychosine (Psy) (galactosylsphingosine), was demonstrated to be a trigger lipid for the inhibition of cytokinesis and the induction of multinuclear giant cells associated with a sphingolipid metabolic disease, globoid cell leukodystrophy (GLD). Indeed, Psy is known to accumulate in the patients' brains. Interestingly, inhibition of sphingolipid biosynthesis also induced multinuclear cells. When cells were treated with a new immunosuppressant, ISP-1/myriocin, which inhibits serine palmitoyltransferase, the first step enzyme of sphingolipid biosynthesis, the cells underwent multinucleation and apoptosis. At present, a definitive model of the function of sphingolipids as to the induction of multinuclear cell formation is not available due to the rudimentary information but possible mechanisms are discussed.

White matter changes mimicking a leukodystrophy in a patient with Mucopolysaccharidosis: characterization by MRI

Mucopolysaccharidosis (MPS) type I (alpha-iduronidase deficiency) is characterized by storage and massive urinary excretion of dermatan sulfate and heparan sulfate; it may be distinguished into three different subtypes based on age at onset and severity of the clinical symptoms. We report on progressive white matter involvement documented by serial MR imaging in a patient with the MPS type I, severe skeletal involvement and preserved mental capabilities (intermediate phenotype or Hurler/Scheie syndrome).The natural history of white matter abnormalities in patients with MPS is still unclear; based on the present study, it appears that degenerative changes of the white matter mimicking a leukodystrophy may mark the course of MPS type I. We also suggest that the degree of MR changes in patients with MPS does not always reflect their neurological impairment.

Saposins (sap) A and C activate the degradation of galactosylsphingosine

As previously shown for [(3)H-galactosyl]ceramide, the breakdown of [(3)H-galactosyl]sphingosine was reduced in prosaposin-deficient skin fibroblast homogenates. Galactosylsphingosine hydrolysis was also deficient in cell homogenates from Krabbe's disease (beta-galactocerebrosidase-deficient) patients, but not acid beta-galactosidase-deficient patients. Moreover, hydrolysis of galactosylsphingosine in the prosaposin-deficient cell homogenates could be partially restored by adding pure saposin A or C, thereby identifying these saposins as essential facilitators of galactosylsphingosine hydrolysis. By contrast, saposins B and D had little effect on galactosylsphingosine hydrolysis in the prosaposin-deficient cells. The reduced galactosylsphingosine turnover in prosaposin-deficiency suggests that there could be a pathogenetic cerebral accumulation of galactosylsphingosine in this disorder.

Identification of a molecular target of psychosine and its role in globoid cell formation

Globoid cell leukodystrophy (GLD) is characterized histopathologically by apoptosis of oligodendrocytes, progressive demyelination, and the existence of large, multinuclear (globoid) cells derived from perivascular microglia. The glycosphingolipid, psychosine (d-galactosyl-beta-1,1' sphingosine), accumulates to micromolar levels in GLD patients who lack the degradative enzyme galactosyl ceramidase. Here we document that an orphan G protein-coupled receptor, T cell death-associated gene 8, is a specific psychosine receptor. Treatment of cultured cells expressing this receptor with psychosine or structurally related glycosphingolipids results in the formation of globoid, multinuclear cells. Our discovery of a molecular target for psychosine suggests a mechanism for the globoid cell histology characteristic of GLD, provides a tool with which to explore the disjunction of mitosis and cytokinesis in cell cultures, and provides a platform for developing a medicinal chemistry for psychosine.

[Familial orthochromatic leukodystrophy: clinicopathological study of two cases]

This paper reports the clinico-pathological data in a French family with orthochromatic leukodystrophy. The parents were first cousins and had seven children. Among those, two sisters and one brother presented with neurological signs, with onset around the 5(th) decade, including a dementing syndrome of frontal type, a tetrapyramidal syndrome, seizures, and, in one sibling, a cerebellar syndrome. CT scan or MRI showed diffuse involvement of the white matter. The neurological signs worsened progressively leading to death within 11 and 22 months. Neuropathological examination was performed in two cases. It revealed characteristic orthochromatic leukodystrophy. In one case, the presence of pigmented macrophages and astrocytes was suggestive of Van Bogaert and Nyssen disease. However there were some atypical features including the absence of pigmented cells in the second case whose clinical course was shorter, and the cavitary appearance of the white matter changes with a relative increase in the number of oligodendrocytes raising the issue of a possible link between this condition and cavitary orthochromatic leukodystrophies.

Epileptic seizures and electroencephalographic evolution in genetic leukodystrophies

The purpose of this study is to explore and compare epileptic seizures and EEG evolution in the various types of genetic leukodystrophy (GL). The authors reviewed the medical records and analyzed 69 serial EEGs in 27 patients with GLs: 13 with late infantile metachromatic leukodystrophy, one with juvenile metachromatic leukodystrophy, one with globoid cell leukodystrophy, six with X-linked childhood adrenoleukodystrophy, one with neonatal adrenoleukodystrophy, four with classic Pelizaeus-Merzbacher disease (PMD), and 1 with connatal Pelizaeus-Merzbacher disease. The diagnoses were made by biochemical and molecular studies. Two or more EEG studies with both awake and sleep traces were recorded during the varying clinical stages for each patient. At the beginning of the GLs, the EEGs were normal or showed mild slowing of background activity. Clinical seizures, mainly of focal origin, with progressive slowing and paroxysmal discharges on EEGs, usually appeared during the later stages of metachromatic leukodystrophy, X-linked childhood adrenoleukodystrophy, and classic Pelizaeus-Merzbacher disease. However, intractable seizures, mainly generalized in nature, and more severe slowing and abundant paroxysmal discharges on EEGs, with commensurate neurologic deterioration, were observed during the earlier course of globoid cell leukodystrophy, neonatal adrenoleukodystrophy, and connatal Pelizaeus-Merzbacher disease. These results indicate that GLs involve not only white matter, but gray matter as well. In all types of GL, there is good correlation between the severity of EEG changes, the severity of the diseases, and the clinical state of the patient.

Partial seizures in leukoencephalopathy with swelling and a discrepantly mild clinical course

We report a patient with 'Leukoencephalopathy with swelling and a discrepantly mild clinical course', an entity of leukoencephalopathy recently clarified. Our patient presented with complex partial seizures in addition to characteristic radiological findings and clinical course. A review of the literature revealed that this new neurodegenerative disease complicates epilepsy in more than half of the patients, and that partial components in the seizure symptomatology are not infrequent.

L-cycloserine slows the clinical and pathological course in mice with globoid cell leukodystrophy (twitcher mice)

Globoid cell leukodystrophy (Krabbe's disease) is an autosomal recessive disease that affects the lysosomal enzyme galactosylceramidase. Galactosylceramidase removes galactose from galactosylceramide and psychosine, which are derived from sphingosine. In the present study, L-cycloserine (an inhibitor of 3-ketodyhydrosphingosine synthase) was administered to the twitcher mouse, an authentic model of globoid cell leukodystrophy. Twitcher mice treated with L-cycloserine had a significantly longer life span and a delayed onset of weight loss than vehicle-injected twitcher mice. Pathological features such as macrophage infiltration and astrocyte gliosis also were less in treated twitcher mice. These results indicate that substrate reduction therapy may have therapeutic value for individuals with residual enzymatic activity, e.g., individuals with late onset disease or individuals with partial enzyme replacement via bone marrow transplantation. In these cases, a reduction in galactosylceramide and psychosine synthesis would enable residual enzymatic activity to keep up with the accumulation of these substrates that would otherwise lead to pathology.

Bone marrow transplantation for globoid cell leukodystrophy, adrenoleukodystrophy, metachromatic leukodystrophy, and Hurler syndrome

Bone marrow transplantation protocols for inherited metabolic storage diseases are unique for each disorder treated. Differences depend also upon how old the patient was when onset occurred and rate of progression of disease. Treatment is directed to prevent or ameliorate the inexorable neurological deterioration that is the major pathophysiological event in all of these inherited metabolic storage diseases.

IL-6 deficiency causes enhanced pathology in Twitcher (globoid cell leukodystrophy) mice

The expression of IL-6 is greatly enhanced in the twitcher mouse (S. M. LeVine and D. C. Brown, 1997, J. Neuroimmunol. 73, 47-56), which is an authentic animal model of globoid cell leukodystrophy (Krabbe's disease). In order to investigate the role of IL-6 in this disease, twitcher/IL-6-deficient mice were generated and the pathology was compared between them and regular twitcher mice. Twitcher/IL-6-deficient mice had a more severe disease than regular twitcher mice: they had an earlier onset day of twitching, a greater number of PAS-positive cells, a greater susceptibility to LPS, an exaggerated gliotic response around some vessels, an elevated level of TNF-alpha, and a compromised blood-brain barrier, which was evaluated by three independent measures. This latter finding indicates that IL-6 plays a role in maintaining the integrity of the BBB, and it raises the possibility that IL-6 functions in a similar manner in other diseases of the CNS. LPS was found to greatly shorten the life of twitcher and twitcher/IL-6-deficient mice compared to genotyped-matched saline-injected mice. This result indicates that a proinflammatory condition can exacerbate an underlying CNS pathology, which could help explain why some leukodystrophy patients display their initial symptoms following a fever or blow to the head.

MRI and electrophysiological abnormalities in a case of canine globoid cell leucodystrophy

A six-month-old West Highland white terrier with progressive, multifocal neurological disease was diagnosed with canine globoid cell leucodystrophy (GCL). Magnetic resonance imaging (MRI) of the brain was performed, as well as electrophysiological testing (including brainstem auditory evoked response, peripheral nerve conduction velocity, repetitive stimulation, F wave analysis and electromyography). MRI findings were consistent with diffuse, symmetrical white matter disease. Electrodiagnostic testing revealed evidence of peripheral neuropathy and an abnormal brainstem auditory evoked response. These observations were consistent with the pathological changes in central and peripheral white matter described for canine GCL, and resembled what has been described in human patients. It is believed that the tests may raise the suspicion of GCL in dogs and may aid in monitoring disease progression.

Effect of psychosine on mitochondrial function

The effect of psychosine on the rate of respiration at different segments of the electron transport chain, respiratory control ratio and the efficiency of phosphorylation was studied. The transfer of electrons through site I, site II and site III was studied independently. The transfer through site I and site III was inhibited by psychosine, whereas the transfer through site II was not inhibited. Cardiolipin, which is essential for the electron transfer through site I and III, was implicated to be responsible for the inhibition of electron transfer by psychosine. Electron carriers of site II are not sensitive to cardiolipin, so psychosine could not inhibit the electron transfer through this site. The ADP/O ratio and respiratory control ratio were inhibited by psychosine showing that it has an uncoupler like effect. Mitochondria isolated from rat liver, kidney and brain behaved essentially the same way in their response to psychosine. Cytochrome c oxidase was significantly inhibited by psychosine and the degree of inhibition was almost same in mitochondria and sub mitochondrial particles. The preence of outer membrane in mitochondria did not make any difference with respect to the action of psychosine on electron transport chain. Psychosine interacts at site I and site III and a change in the lipid environment of the membrane is responsible for the mitochondrial dysfunctions induced by psychosine. This represents a possible mechanism for the destruction of cells in Gaucher's and Krabbe's disease.

Adult onset Krabbe's leukodystrophy: a report of 2 cases

Krabbe's disease with adult onset is rare; neurological symptoms begin in childhood or at a juvenile age. Two brothers with adult onset of the disease are here reported; 1 sibling developed parapareto-ataxic gait while the other was asymptomatic. Magnetic resonance imaging showed areas of demyelination in the white matter of the brain, while nerve conduction was completely normal. In both patients deficiency of galactosylceramide beta-galactosidase was comparable to the infantile form.

Early infantile Krabbe disease: deceptively normal magnetic resonance imaging and serial neurophysiological studies

Early infantile Krabbe disease is a progressive neurodegenerative disease caused by deficiency of lysosomal enzyme galactocerebroside beta-galactosidase, with onset before the age of 6 months. We present serial clinical, radiological and neurophysiological findings of a patient with early infantile Krabbe disease, presenting at the third day of life with hypotonia, macrocephaly and neonatal seizures. The patient had a deceptively normal initial magnetic resonance imaging examination at the age of 3 months, with progression of the white matter disease over the following 9 months, showing a clinical picture of profound hypotonia with pyramidal and pseudobulbar signs, as well as mild optic atrophy. Assay of galactocerebroside beta-galactosidase activity in leukocyte culture disclosed a marked deficiency of the enzyme (0.00 nmol/mg protein per h with normal values > 0.7 nmol/mg protein per h), thus confirming the diagnosis of Krabbe disease. Nerve conduction velocity and evoked potential studies, as well as the electroencephalogram, were abnormal at the age of 6 months, while serial neurophysiological studies at the age of 12 and 18 months demonstrated the progressive nature of the disease.