Early infantile form of Krabbe disease: a case report

A 7-month-old female child, born to 2nd degree consanguineous marriage brought with complaints of gross developmental delay. Her examination revealed spasticity in all 4 limbs with brisk deep tendon reflexes with intact primitive reflexes and exaggerated startle reflex. Her MRI brain showed demyelination signs in bilateral thalami, dentate hila, and thickened optic chaisma. Age of presentation, clinico-radiological findings were suggestive of early infantile form of Krabbe disease.

Krabbe Disease Associated With Mitochondrial Dysfunction in a Chinese Family

Background: Krabbe disease is caused by biallelic mutations of GALC gene. NDUFAF1 gene mutations are related to mitochondrial encephalopathy. To date, there has been no report on the co-pathogenesis of these two gene mutations. There were three children in a family who presented with global developmental retardation. MRI showed lesions in the white matter and dentate nucleus of the cerebellum.Methods: Clinical data of the proband and her family members were gathered in a retrospective manner. Karyotype, FISH, whole exome sequencing was performed using genomic DNAs extracted from peripheral blood samples. Enzyme activities of galactosylceramidase (GALC) and mitochondria were determined to verify gene functions.Results: This study reported a pedigree of leukoencephalopathy, in which 3 of the 4 children showed phenotypes of developmental delay, hearing/visual impairment, and peripheral neuropathy. Mutations of NDUFAF1 (c.278A>G; p. His93Arg, c.247G> A; p. Asp83Asn) and GALC (c.599C>A; p.Ser200*) were identified in all three cases. The proband's parents carried these mutations as a heterozygous state. Clinical features, MRI changes, enzyme activity of GALC, and mitochondrial function analysis demonstrated that this pedigree was caused by GALC and NDUFAF1 gene mutations working together.Conclusion: We first report a pedigree of Krabbe disease with biallelic mitochondrial gene NDUFAF1 mutations. For multiple gene mutations found in genetic testing, clinical phenotypes, gene functions, and family history should be comprehensively analyzed. Gene panel examination may miss pathogenic mutations, and prenatal diagnosis of patients with polygenic inheritance needs careful consideration.

Krabbe Disease: Prospects of Finding a Cure Using AAV Gene Therapy

Krabbe Disease (KD) is an autosomal metabolic disorder that affects both the central and peripheral nervous systems. It is caused by a functional deficiency of the lysosomal enzyme, galactocerebrosidase (GALC), resulting in an accumulation of the toxic metabolite, psychosine. Psychosine accumulation affects many different cellular pathways, leading to severe demyelination. Although there is currently no effective therapy for Krabbe disease, recent gene therapy-based approaches in animal models have indicated a promising outlook for clinical treatment. This review highlights recent findings in the pathogenesis of Krabbe disease, and evaluates AAV-based gene therapy as a promising strategy for treating this devastating pediatric disease.

National U.S. Patient and Transplant Data for Krabbe Disease

Krabbe disease (KD) is a leukodystrophy caused by mutations in the galactosylceramidase gene. Presymptomatic hematopoietic stem cell transplantation (HSCT) is associated with improved outcomes, but most data are from single-center studies. Our objective was to characterize national patterns of HSCT for KD including whether there were disparities in HSCT utilization and outcomes. We conducted a retrospective study of KD patients ≤ age 18 years from November 1, 2015, through December 31, 2019, using the U.S. Children's Hospital Association's Pediatric Health Information System database. We evaluated outcomes for HSCT, intensive care unit days, and mortality, comparing age, sex, race/ethnicity, rural/urban location, and median household income. We identified 91 KD patients. HSCT, performed in 32% of patients, was associated with reduced mortality, 31 vs. 68% without HSCT (p < 0.003). Trends included the fact that more males than females had HSCT (39 vs. 23%); more Asian and White patients had HSCT compared to Black or Hispanic patients (75, 33, 25, and 17%, respectively); and patients from households with the lowest-income quartile (< $25,000) had more HSCT compared to higher-income quartiles (44 vs. 33, 30, and 0%). Overall, receiving HSCT was associated with reduced mortality. We noted trends in patient groups who received HSCT. Our findings suggest that disparities in receiving HSCT could affect outcomes for KD patients.

Formation of multinucleated globoid cells in Krabbe iPSC-derived microglia cultures: a preliminary investigation

Globoid cell leukodystrophy (Krabbe disease) is a severe demyelinating, neurodegenerative lysosomal storage disorder caused by deficiency in glycosphingolipid catabolic enzyme galactosylceramidase (GALC). Histologically, Krabbe disease is characterized by the appearance of large multinucleated globoid cells that express classical macrophage markers (both of brain-resident microglia and peripheral monocyte-derived). Globoid cells reside near areas of degeneration; however, their functional significance in disease progression remains unclear. In the current study, we differentiated microglia-like cells from iPSCs from a donor with infantile Krabbe disease and compared them to microglia generated from two healthy controls and two donors with the lysosomal storage disorder metachromatic leukodystrophy (MLD), which is genetically distinct from Krabbe disease but presents similarly in terms of severity of demyelination and neurodegeneration. We report the novel finding of prominent formation of giant multinucleated globoid cells from the microglia derived from the Krabbe donor, but not from healthy control or MLD donors. The Krabbe microglia displayed reduced IL-6 protein expression upon stimulation with lipopolysaccharide, and the multinucleated globoid cells themselves appeared deficient in phagocytosis of both disease-relevant myelin debris and E. coli, together hinting at an impairment of normal function. The formation of the globoid cells could be attenuated by fully replacing the medium following passaging, suggesting that yet-to-be determined secreted factors are influencing cell fusion in our culture system. While preliminary, our results imply that globoid cells may be detrimental in Krabbe disease by hindering the normal function of brain-residing macrophages.

Prion-like α-synuclein pathology in the brains of infants: Krabbe disease as a novel seed-competent α-synucleinopathy

Krabbe disease (KD) is an infantile neurodegenerative disorder resulting from pathogenic variants in the GALC gene which causes accumulation of the toxic sphingolipid psychosine. GALC variants are associated with increased risk of Lewy body diseases (LBD), an umbrella term for age-associated neurodegenerative diseases in which the protein α-synuclein aggregates into Lewy bodies. To explore whether α-synuclein in KD has pathological similarities to that in LBD, we compared post-mortem KD tissue to that of infant control cases and identified alterations to α-synuclein localisation and expression of modifications associated with LBD. To determine whether α-synuclein in KD displayed pathogenic properties associated with LBD we evaluated its seeding capacity using the real-time quaking-induced conversion assay. Strikingly, seeded aggregation of α-synuclein resulted in the formation of fibrillar aggregates similar to those observed in LBD, confirming the prion-like capacity of KD-derived α-synuclein. These observations constitute the first report of prion-like α-synuclein in the brain tissue of infants and challenge the putative view that α-synuclein pathology is merely an age-associated phenomenon, instead suggesting it can result from alterations to biological processes such as sphingolipid homeostasis. Our findings have important implications for understanding the mechanisms underlying Lewy body formation in LBD.

Advances in the Diagnosis and Treatment of Krabbe Disease

Krabbe disease is an autosomal recessive leukodystrophy caused by pathogenic variants in the galactocerebrosidase (GALC) gene. GALC activity is needed for the lysosomal hydrolysis of galactosylceramide, an important component of myelin. While most patients are infants, older patients are also diagnosed. Starting in 1970, a diagnosis could be made by measuring GALC activity in leukocytes and cultured cells. After the purification of GALC in 1993, the cDNA and genes were cloned. Over 260 disease-causing variants as well as activity lowering benign variants have been identified. While some pathogenic variants can be considered “severe,” others can be considered “mild.” The combination of alleles determines the type of Krabbe disease a person will have. To identify patients earlier, newborn screening (NBS) has been implemented in several states. Low GALC activity in this screening test may indicate a diagnosis of Krabbe disease. Second tier testing as well as neuro-diagnostic studies may be required to identify those individuals needing immediate treatment. Treatment of pre-symptomatic or mildly symptomatic patients at this time is limited to hematopoietic stem cell transplantation. Treatment studies using the mouse and dog models have shown that combining bone marrow transplantation with intra-venous gene therapy provides the best outcomes in terms of survival, behavior, and preservation of normal myelination in the central and peripheral nervous systems. With earlier diagnosis of patients through newborn screening and advances in treatment, it is hoped that more patients will have a much better quality of life.