Definition of Morquio syndrome

Reviewed on 6/3/2021

Morquio syndrome: An inherited error in carbohydrate metabolism that results in mucopolysaccharide accumulation and severe skeletal defects. The defects are present at birth and include severe deformity of the spine and chest, short neck, loose and enlarged joints, and irregular ends of the long bones. The disorder is inherited in an autosomal recessive manner.

To give a synopsis of the disease: There is severe growth retardation (adult height 82 to 115 cm); the skull is unusually thick and dense; there are corneal opacities (clouding of the eyes) and hearing loss. The liver is slightly enlarged. There are multiple abnormalities of the spine (platyspondyly, odontoid hypoplasia, cervical subluxation and cervical myelopathy). The chest is pigeon-shaped (pectus carinatum). There is joint laxity and knock knees (genu valgum) and hip deformity (dysplasia). The intelligence is normal. (In other words, there is no tendency to mental retardation.) There are multiple abnormal lab findings (galactosamine-6-sulfatase deficiency in fibroblasts and amniocytes, keratan sulfaturia that decreases with age, and metachromasia of white blood cells and fibroblasts). The error in carbohydrate metabolism is a deficiency of the enzyme galactosamine-6-sulfatase. Enzyme replacement therapy has not been effective to date. Prenatal diagnosis is feasible by amniocentesis. As mentioned, the inheritance is autosomal recessive, meaning that the parents who seem normal each carry one Morquio gene and their boys and girls each run a 1 in 4 (25%) risk of receiving both of the parental Morquio genes and having the disease. The Morquio gene is located on chromosome 16 (in chromosome subband 16q24.3).

The condition was first described, simultaneously and independently in 1929, by Luis Morquio in Montevideo, Uruguay, and by JF Brailsford in Birmingham, England. They both recognized the occurrence of corneal clouding, aortic valve disease, and urinary excretion of keratosulfate. Morquio observed the disorder in 4 sibs in a family of Swedish extraction and, to further compound the international melange, reported his observations in French (Sur une forme de dystrophie osseuse familiale. Bull. Soc. (Pediat. Paris 27: 145-152, 1929). The disease should be called Morquio-Brailsford (or the reverse) syndrome, but this is rarely done. However, Morquio syndrome is sometimes called by its biochemical name -- Mucopolysaccharidosis Type IV. (MPS IV)


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