Gene therapy in a child with mucopolysaccharidosis type I - Case report of the first successful gene treatment of a Slovenian patient abroad

Mucopolysaccharidoses are a group of lysosomal storage diseases. Their common feature is the lack of enzymes that break down glycosaminoglycans, polysaccharides that bind to proteoglycans and form the extracellular matrix. Because there are no enzymes that break down glycosaminoglycans, they accumulate in lysosomes and cause damage to them. Consequently, they damage other cellular organelles, cells, and finally, organs. The clinical picture is broad, ranging from neurocognitive decline, musculoskeletal deformities, and coarse facial features. Although we are currently unable to cure the disease, the sooner a diagnosis is made, the better the treatment outcome may be in slowing down the course of the disease. A promising treatment is gene therapy, which suggests the possibility of curing the disease. Early detection of the disease is crucial. In this clinical case, we present a boy where early cognitive decline, and signs typical of the disease were identified. He was referred to a tertiary institution, where the diagnosis was confirmed. In July 2018, he underwent experimental gene therapy as part of a clinical study abroad (San Raffaele Hospital, Milan, Italy). To our knowledge, this is the first successfully performed gene therapy in a Slovenian patient and, at the same time, one of the first cases of gene therapy of mucopoly-saccharidosis type I on a global scale. Gene therapy has become part of our clinical reality, and it represents an important milestone in the treatment of inborn diseases. It would make sense to introduce newborn screening for MPS type I, which is not yet carried out in Slovenia or Europe. Until then, the most important prerequisite for successful treatment remains early clinical recognition of the disease and referral to a tertiary health care facility.