Morquio Syndrome/Mucopolysaccharidosis IV
(Occurs in 1/40,000 to 1/200,000 births with Type A being 95% and Type B 5% of cases)
Morquio Syndrome is a mucopolysaccharide storage disease that is autosomal recessive. MPSBoth lead to an accumulation of keratan sulfate (KS) in the cells and tissues of the body. The accumulation of KS in the cornea and bone leads to reduced vision and skeletal deformities, respectively. There are two forms to this disorder the severe form, MPS IVA, which shows between ages one and three and presents with knock-knees and breastbone prominence and the slow progressive form, MPS IVB, which has fewer clinical symptoms and is milder, shows anywhere up to adolesence and presents with hip pain and stiffness. The two types can only be distinguished apart by genetic analysis which shows that MPS IVA occurs because of a deficiency of the enzyme N-acetyl-galactosamine-6-sulfatase (GALNS) and MPS IVB occurs due to a deficiency of beta-galactosidase. This leads to accumulation of mucopolysaccharides in the body, abnormal skeletal development, and other additional symptoms. Most cases of MPS IV have normal intelligence.
Symptoms of MPS IV may include growth delays; a prominent lower face; abnormal sideways and front-to-back or side-to-side curvature of the spine (kyphoscoliosis) or concern for a spine abnormality; an abnormally short neck; knees that are abnormally close together (knock knees or genu valgum); flat feet; abnormal development of the growing ends of the long bones (epiphyses); hip dislocation and arthritis and/or a prominent breast bone (pectus carinatum). Hearing loss, weakness of the legs, and/or additional abnormalities may also occur. The elbows, wrists, hips, knees and other large joints are abnormally flexible, causing overall instability. High frequency hearing impairment is common.
Affected children have a characteristic facial appearance that may include an enlarged head, broad mouth, prominent cheekbones, an unusually small nose, widely spaced and thinly enameled teeth, and widely separated eyes with subtle corneal clouding. Affected individuals who are ambulatory willl exhibit a waddling gait with frequent falls.
Skeletal X-rays typically show marked flattening of the vertebra. The long bones of the arms and legs are characteristically shorter and thicker than normal. The skull is large for the rest of the body. The connection between the first and second vertebrae in the neck is poorly developed and this abnormality can be life threatening. A trivial injury may cause the two vertebrae to slip on each other and compress the spinal cord. Surgery to stabilize the upper cervical spine, usually by spinal fusion, can be lifesaving but life expectancy is decreased somewhat despite surgery. The deformity of the chest causes a strain on the heart and lungs, which may eventually cause respiratory failure.
MPS IVA can be treated with enzyme replacement therapy though there is no treatment at this time for MPS IVB. Surgery to decompress and fuse the bones of the upper neck to the base of the skull can prevent destabilization of the cervical vertebrae and potential damage to the spinal cord. The placement of a bioprosthetic or prosthetic valve may be required for affected induvial with ventricular hypertrophy. Enlarged tonsils and adenoids may need to be removed in order to relieve upper-airway obstruction and sleep apnea. Additionally, ventilation tubes and hearing aids may be needed for individuals with hearing loss. Penetrating keratoplasty (corneal replacement) may be needed to treat corneal opacification (scarring or clouding of the cornea), which causes impaired vision.
Children with MPS IVA are of normal intelligence, they usually attend regular classes, but they made need to sit close to the front of the classroom if they have difficulties hearing or seeing. They may also need to use a wheelchair around school grounds.
Additional booklets about the disorder are attached as well:
