Mucopolysaccharidosis type IVA in children: Clinical cases

Background. Mucopolysaccharidosis type IVA (Morquio syndrome) is a rare genetic lysosomal storage disease. Due to rarity, the syndrome is typically diagnosed at a later stage of gross affections of musculoskeletal and central nervous systems, leading to disability and a markedly reduced quality of life. A replacement therapy is nowadays available with recombinant human N-acetylgalactosamine-6-sulfatase (elosulfase alfa) enzyme.

Clinical cases description. Two siblings, 10-yo male and 8-yo female, were admitted with complaints of growth retardation, deformity of the spine, thorax and joints, impaired hearing and visual acuity, poor tolerance to exercise. In the boy’s medical history, first manifestations appeared in the first year of life and progressed gradually; the patient was being observed as spondylodysplastic. Mental development was unaffected. The diagnosis was confirmed only by age of 7 at the National Medical Research Center for Children's Health Federal State Autonomous Institution of the Ministry of Health of the Russian Federation. Genotyping revealed two SNP mutations in gene GALNS (g.88909227C>A and g.88884454G>A in heterozygous state), and enzymatic assays — a severely reduced N-acetylgalactosamin-6-sulfatase activity. A routine elosulfase alfa replacement therapy has been received since 8-year age.

The younger sister had neonatal cardiomegaly; congenital carditis and cardiomyopathy not excluded. Musculoskeletal affections developed by age of 3–4 years. By age of 5 and simultaneously with brother, the same GALNS mutations and severely impaired N-acetylgalactosamine-6-sulfatase activity were detected. A replacement therapy has been routinely received since 6-year age. The therapy triggered positive dynamics of restoring activity and muscle strength in both children, as well as significantly abating the musculoskeletal affection progress.

Conclusion. The clinical cases of Morquio syndrome presented demonstrate its long-term and complex diagnosis. A replacement therapy is nowadays available, which warrants an earliest disease detection to halt progression and improve the patient’s life quality and expectancy.