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-acetyl-galactosamine-6-sulfatase and
β-galactosidase, respectively. 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.
Short stature and marked varus gonarthrosis (knock knees) in a
patient with Morquio syndrome.
Characteristic facies with mild coarsening, midface hypoplasia, and
macroglossia in a young boy with Morquio syndrome.
Mucopolysaccharidosis Type IV; Morquio-Silfverskiöld
Syndrome Morquio-Brailsford Syndrome; Morquio-Ullrich Syndrome; Atypical
Chondrodystrophy; Dysotosis 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
Type A: Morquio Syndrome A; Galactosamine-4-Sulfatase (GALNS) Deficiency
Type B: Morquio Syndrome B; Morquio-Like Syndrome; β-Galactosidase
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.
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 mucopolysacchidosis.
Deficiency of N-acetylgalactosamine-6-sulfate
sulfatase (type A) or β-galactosidase (type B) leads to storage of
keratan sulfate in tissues.
Two types lead to identical phenotype. Keratan sulfate
in urine. Specific enzyme assay diagnostic.
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 third or fourth decade. May have aortic insufficiency.
Hypoplasia of the odontoid is common, causing atlantoaxial subluxation and
cord compression. Platyspondyly. Tracheal collapse with flexion of the neck
reported. Very thin teeth enamel in type A. Progressive hearing loss.
Assess cardiorespiratory status
carefully and obtain appropriate investigations, for example,
echocardiogram. Assess airway carefully. Obtain radiographs of cervical spine. Sleep ...