What is Mucopolysaccharidosis Type IIIA?
Mucopolysaccharidosis type III, or Sanfilippo syndrome, consists of four disease sub-types, based on the gene that causes the disease. All sub-types of MPS III are inherited lysosomal storage disorders and have similar clinical features. Mucopolysaccharidosis type IIIA (MPS IIIA), also known as Sanfilippo syndrome Type A, is caused by harmful changes (mutations) in the SGSH gene. The symptoms associated with MPS IIIA are caused by a buildup of harmful substances in the central nervous system and cause progressive destruction of nerve cells. The severity of the disease can range from mild to severe, even among affected individuals in the same family.
While infants with MPS IIIA appear normal at birth, delays in speech and motor skills may begin before one year of age, and nearly all children will experience some sort of developmental delay before six years of age. Children often have recurrent ear, nose, and throat infections. Behavioral issues, such as aggressiveness, sleeplessness, and hyperactivity, typically develop in early childhood, often between the ages of three and five. Intellectual disability becomes more severe during this time period, in part because seizures frequently develop. Many children start to lose the ability to speak by age 10. Motor problems, such as difficulty swallowing and stiff or rigid muscles (spasticity), will also develop. Affected individuals may also experience recurrent diarrhea and hearing loss. Most individuals with MPS IIIA lose the ability to walk by their mid-teens. Physical features of the disease can include coarse facial features, skeletal abnormalities, a large head (macrocephaly), and thick or excess body hair (hirsutism).
How common is Mucopolysaccharidosis Type IIIA?
MPS IIIA is the most common form of Mucopolysaccharidosis type III and is observed in approximately 1 in 100,000 individuals. The disease is observed more frequently in the Cayman Islands, with some estimates as high as 1 in 400 births.
How is Mucopolysaccharidosis Type IIIA treated?
There is currently no cure for MPS IIIA. The treatment for MPS IIIA is based on the patient's particular symptoms and may include speech or occupational therapy for developmental delays, medication to treat seizures and recurrent infections, and ear tubes or hearing aids. Feeding tubes may be required in later stages of the disease. Overall, treatment is intended to relieve pain and increase the quality of life (palliative).
What is the prognosis for an individual with Mucopolysaccharidosis Type IIIA?
MPS IIIA is a progressive disease that has no cure, and individuals have a shortened lifespan. Most individuals with MPS IIIA do not survive past the second or third decade of life, with an average lifespan of approximately 15 years. However, there are rare reports of individuals with MPS IIIA who have lived into their fourth or fifth decade.