Newborn screening · Lysosomal storage disorder
Infantile Krabbe Disease · KD
Lysosomal storage disorder. Pre-symptomatic stem cell transplant alters the trajectory of severe forms.
Description
Krabbe disease, globoid cell leukodystrophy, is an autosomal recessive lysosomal storage disorder. Two damaging copies of GALC on chromosome 14q31 reduce or abolish galactocerebrosidase activity. The enzyme breaks down galactosylceramide and psychosine, and psychosine in particular accumulates to toxic levels in oligodendrocytes and Schwann cells. The result is rapid loss of central and peripheral myelin and the appearance of multinucleated globoid cells in the white matter that gave the disease its histologic name. Inheritance is autosomal recessive. Reported birth incidence is roughly 1 in 100,000 in the United States, with founder clusters in specific Druze and Israeli populations.
The early infantile form, onset before six months, accounts for the majority of cases. Infants present with irritability, feeding difficulty, hypertonia, and developmental regression. Disease progresses to seizures, blindness, deafness, and death typically before age two without treatment. Later onset forms (late infantile, juvenile, adult) are clinically heterogeneous and slower in trajectory. Diagnosis combines decreased GALC enzyme activity in leukocytes or fibroblasts with biallelic GALC variants. Brain magnetic resonance imaging shows symmetric white matter signal change, and cerebrospinal fluid protein is typically elevated. Psychosine measurement on dried blood spot has emerged as a key second-tier marker that helps distinguish the severe early infantile phenotype from milder GALC variants and pseudodeficiency alleles.
New York State began statewide newborn screening for Krabbe disease in August 2006, the first state to do so, after advocacy led by Jim and Cindy Kelly following the diagnosis of their son Hunter. Krabbe disease was added to the federal Recommended Uniform Screening Panel in February 2024.
Treatments to date
There is no approved disease-specific drug for Krabbe disease. Allogeneic hematopoietic stem cell transplant (HSCT), typically using umbilical cord blood, is the only intervention that alters the trajectory of the early infantile form. Donor-derived microglia cross into the central nervous system and provide a continuous source of GALC enzyme. Outcomes depend almost entirely on timing. Escolar et al. (New England Journal of Medicine, 2005) reported that children with infantile Krabbe transplanted before symptom onset, generally before 30 days of life, had favorable neurodevelopmental outcomes compared with children transplanted after symptoms appeared, who showed disease progression similar to untreated controls. Long-term follow-up reports continued motor disability in many transplanted children, but cognitive function and survival were preserved in the pre-symptomatic group.
The pre-symptomatic versus post-symptomatic gap is the basis for newborn screening. The window from positive screen to transplant is narrow, and screening programs have built rapid referral pathways to high-volume transplant centers, primarily Duke and the University of Pittsburgh, to meet the 30-day target.
Substrate reduction therapy with L-cycloserine and other psychosine-lowering strategies has been explored in mouse models. AAV-mediated gene therapy programs targeting central nervous system delivery of GALC are in clinical development, and combination strategies pairing HSCT with intrathecal AAV gene therapy are being studied in an effort to address the residual peripheral nervous system and motor outcomes that transplant alone leaves behind.