Fucosidosis is a rare autosomal recessive lysosomal disorder caused by alpha-fucosidase deficiency. We report a child with fucosidosis, second daughter of non-consanguineous parents, for whom biochemical diagnosis followed clinical evidence of the disease in her older sister. Based on previous experiences, the indication to transplant was considered. Since she lacked a matched sibling, an unrelated marrow donor was found. At pre-hematopoietic stem cell transplantation evaluation, first signs of neurological involvement were clinically detectable. MRI showed diffuse hypomyelination and auditory brainstem responses and somatic-sensorial evoked potentials were altered. Visual evoked potentials were normal, tortuosity in the retinal veins and peripapillary hemorrhages were detected. Bone marrow transplantation conditioning was with a regimen of busulphan, thiotepa and cyclophosphamide; in vivo Campath 1G, cyclosporin A and short course methotrexate were given to prevent graft-versus-host disease. The patient engrafted rapidly and her post-transplant course was complicated by moderate graft-versus-host disease, transient episodes of idiopathic thrombocytopenic purpura, repeated septic complications and recurrent episodes of Sweet's syndrome. Sequential short tandem repeat polymorphisms on peripheral blood and bone marrow cells documented the persistence of donor engraftment. Follow-up showed a progressive rise of enzymatic levels. Psychomotor development improved, as confirmed by evaluation of evoked potentials and by MRI scanning.