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At a glance

It is an inborn error of metabolism characterized by the deficiency of one of 10 specific lysosomal enzymes, resulting in an inability to metabolize complex carbohydrates (mucopolysaccharides) into simpler molecules. It exists in two forms: Morquio Syndromes A and B are caused by a deficiency in the enzyme N-acetylgalactosamine-6-sulfatase and β-galactosidase, respectively. It may be detected as early as 18 months to 2 years. The skeletal abnormalities may include macrocephaly, a broad mouth, prominent cheekbones, an unusually small nose, short necks, short barrel chests, disproportionately long arms, enlarged and possibly hyperextensible wrists, stubby hands, and “knock knees.” The joint laxity and bony abnormalities of the spine can result in life-threatening spinal cord compression. The presence of a thoracic kyphoscoliosis may contribute to spinal cord ischemia risk during positioning. Aortic regurgitation and deafness have been reported.

Synonyms

Mucopolysaccharidosis Type IV; Morquio-Silfverski öld Syndrome; Morquio-Brailsford Syndrome; Morquio-Ullrich Syndrome; Atypical Chondrodystrophy; Dysostosis Enchondralis Metaepiphysaria; Eccentrochondrodysplasia; Eccentro-Osteochondrodysplasia; Familial Osseous Dystrophy; Hereditary Chondrodysplasia; Hereditary Osteochondrodystrophy; Hereditary Polytopic Enchondral Dysostosis; Keratansulfaturia; KS Mucopolysaccharidosis; Osteochondrodystrophia Deformans; Osteochondrodystrophy; Spondyloepiphyseal Dysplasia; Silfverskiöld Syndrome.

History

First described by L. Morquio, a Uruguayan pediatrician, in 1929 while living in Montevideo, Uruguay. He observed the disease in four sibs in a Swedish family. It is also suggested that J. F. Brailsford, a British pediatrician from Birmingham, England, simultaneously described the disease.

Classification

  • Type A: Morquio Syndrome A; Galactosamine-4-Sulfatase (GALNS) Deficiency

  • Type B: Morquio Syndrome B; Morquio-Like Syndrome; β-Galactosidase Deficiency

Morquio Syndrome: Short stature and marked varus gonarthrosis (knock knees) in a patient with Morquio Syndrome.

Morquio Syndrome: Characteristic facies with mild coarsening, midface hypoplasia, and macroglossia in a young boy with Morquio Syndrome.

Incidence

It is estimated between 1:40,000 and less than 1:200,000 live births. In the United States, it is estimated that 1 in 25,000 births results in some form of mucopolysaccharidosis.

Genetic inheritance

It is inherited as an autosomal recessive.

Pathophysiology

Deficiency of N-acetylgalactosamine-6-sulfate sulfatase (type A) or β-galactosidase (type B) leads to storage of keratan sulfate in tissues.

Diagnosis

Two types lead to identical phenotype. The presence of keratan sulfate in urine is used to confirm the diagnosis. The use of specific enzyme assay is essential to establish the diagnostic.

Clinical aspects

Affected children have normal mental development, but severe physical manifestations. Short trunk, lax joints, short neck, corneal clouding, midface hypoplasia with mild coarsening of the facies. Progressive kyphoscoliosis leads to cardiorespiratory failure with death from cor pulmonale in ...

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