What is Mucopolysaccharidosis Type IIIC?
Mucopolysaccharidosis type IIIC (MPS IIIC), also known as Sanfilippo syndrome Type C, is caused by harmful changes, or mutations, in the HGSNAT gene. Mucopolysaccharidosis type III, or Sanfilippo syndrome, consists of four disease sub-types, based on the gene that causes the disease and MPS IIIC is one of these sub-types. All sub-types of MPS III are inherited, lysosomal storage disorders, and they all have similar clinical features. The symptoms associated with MPS IIIC are caused by a buildup of harmful substances in the central nervous system that causes progressive destruction of nerve cells. The severity of the disease can range from mild to severe, even among affected individuals in the same family.
Infants with MPS IIIC appear normal at birth and generally do not have any delay in development for the first year of life. Delay in speech and motor skills usually begin in early childhood, 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 ages three and five years. Intellectual disability becomes more severe during this time period, in part because seizures frequently develop. Affected individuals may experience recurrent diarrhea and hearing loss. Many individuals will lose the ability to speak in the teenage years. Motor problems, such as difficulty swallowing and stiff or rigid muscles (spasticity), will also develop. Most individuals with MPS IIIC lose the ability to walk before age 30. Physical features of the disease can include coarse facial features, skeletal abnormalities, a large head (macrocephaly), and thick or excess body hair (hirsutism). Some individuals may develop heart problems as they get older.
How common is Mucopolysaccharidosis Type IIIC?
The incidence of MPS IIIC is estimated at 1 in 1,000,000 live births.
How is Mucopolysaccharidosis Type IIIC treated?
There is currently no cure for MPS IIIC. The treatment for MPS IIIC is based on the particular symptoms, and it is generally intended to make individuals more comfortable. This can 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 IIIC?
MPS IIIC is a progressive disease that has no cure, and individuals have a shortened lifespan. Death typically occurs in the third or fourth decade of life, with an average lifespan of approximately 34 years. Death is often due to respiratory issues.