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Mucopolysaccharidoses (MPS) - Type 4A

Name of disease:

Mucopolysaccharidoses )MPS) - Type 4A

ICD-10 diagnosis code:

E76.2

Causes:

Most cases of mucopolysaccharidosis type 4A are autosomal recessive It is caused by the mutation of GALNS gene, leading to the deficiency of GALNS enzymes.

Mode of inheritance:

Mucopolysaccharidosis Type 4A can be sporadic or is inherited from parents in family in autosomal recessive pattern

Diagnosis:

The diagnosis of Mucopolysaccharidosis Type 4A is based on medical history, physical examinations and skeletal X-ray. It can be confirmed by low GALNS enzyme activity in blood culture. Molecular genetic testing can also be used to detect mutation of GALNS gene.

Age of onset:

Infancy (usually second year of life)

Common signs and symptoms:

Progressive skeletal and joint deformities Impairment in walking and daily activities Kyphosis, scoliosis and long bone deformities Joint hyperlaxity (neck, hands, fingers, hips, knees) Short stature Respiratory impairment and susceptibility to pneumonia Sleep apnea Hearing loss Corneal clouding Dental hypoplasia

Available treatments (medicinal and non-medicinal):

Currently, GALNS enzyme replacement therapy is used to treat mucopolysaccharidosis type 4A. Other treatment is symptomatic and supportive.

Disease management tips:

For patients with neck bone problem, surgery to decompress and fuse bones of the upper neck to the base of the skull could be done to prevent instability of cervical vertebrae and potential damage to spinal cord Physical rehabilitation and physiotherapy shall be used if patients have progressive skeletal and joint deformities, which impair their walking and daily activities. For patients with sleep apnea, enlarged tonsils may need to be removed. Corneal replacement might be needed to treat the clouding of cornea. Children with mucopolysaccharidosis type 4A are of normal intelligence so they could attend regular classes. However, they shall sit close to the front of the classroom if they have difficulties in hearing or seeing.

References:

https://rarediseases.org/rare-diseases/morquio-syndrome/ https://rarediseases.info.nih.gov/diseases/3785/mucopolysaccharidosis-type-iva

Other useful websites:

More about the disease:https://medlineplus.gov/genetics/condition/mucopolysaccharidosis-type-iv/ Patient groups: Hong Kong Mucopolysaccharidoses & Rare Genetic Diseases Mutual Aid Grouphttp://mps.org.hk/en/home/