Mucopolysaccharidosis type IIIC (MPS IIIC), also known as Sanfilippo Type C syndrome, is a progressive lysosomal storage disorder. The features of MPS IIIC are due to the build up of glycosaminoglycans (GAGs), important complex carbohydrates responsible for many regulatory functions in the body. This build up primarily affects the central nervous system. 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. The onset of symptoms including developmental delay and speech delay usually occurs between one to four years of age. Behavioral issues, such as aggressiveness and hyperactivity, typically develop in early childhood, often between ages of three and six years. Intellectual disability becomes more severe during this time period. Motor problems, such as difficulty swallowing and spasticity (stiff or rigid muscles), will also develop. The physical features of the disease, such as coarse facial features, skeletal abnormalities, and macrocephaly (large head) are often mild.
Some individuals have developed retinitis pigmentosa, which causes deterioration of the light sensing cells of the eye leading to progressive vision loss.
The incidence of MPS IIIC varies significantly by region. Where estimates have been made, the incidence ranges from 1 in 235,000 and 1 in 3,200,000 with an average incidence of approximately 1 in 737,000.
There is currently no approved treatment or cure for MPS IIIC.
Symptoms begin in early childhood. Death typically occurs in the second or third decade of life, though survival into the fourth decade has been reported.
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