Morquio syndrome

Morquio syndrome, also classified as mucopolysaccharidosis type IV, is a rare inherited metabolic disorder in which the body cannot properly break down a class of complex sugar molecules called glycosaminoglycans, and in this condition specifically keratan sulfate builds up progressively in tissues throughout the body. It is inherited in an autosomal recessive pattern, meaning a child must receive a non-working copy of the responsible gene from each parent; Type A results from mutations in the GALNS gene, which normally produces the enzyme galactosamine-6 sulfatase, while the generally milder Type B involves the GLB1 gene and the enzyme beta-galactosidase. Affected infants usually appear healthy at birth, with symptoms emerging between one and three years of age as skeletal problems develop, including a bell-shaped chest, curvature of the spine, shortened long bones and joint laxity; growth typically stalls by around age eight. Additional effects can include hearing loss, clouding of the corneas, heart valve disease and breathing difficulties from a narrowed airway and chest deformity. Diagnosis relies on enzyme activity testing and confirmatory genetic analysis. Since 2014 an enzyme replacement therapy, elosulfase alfa, has been approved specifically for Type A, easing some systemic effects, though no approved disease-modifying treatment yet exists for Type B beyond supportive and prenatal care.