Question: What is (are) Mucopolysaccharidosis type IIIC ?
Answer: Mucopolysaccharidosis type IIIC (MPS IIIC) is an genetic disorder that makes the body unable to break down large sugar molecules called glycosaminoglycans (GAGs, formerly called mucopolysaccharides). Specifically, people with this condition are unable to break down a GAG called heparan sulfate. Affected individuals can have severe neurological symptoms, including progressive dementia, aggressive behavior, hyperactivity, seizures, deafness, loss of vision, and an inability to sleep for more than a few hours at a time. MPS IIIC results from the missing or altered enzyme acetyl-CoAlpha-glucosaminide acetyltransferase. This condition is inherited in an autosomal recessive manner. There is no specific treatment. Most people with MPS IIIC live into their teenage years; some live longer.
Source: GARD

Question: What are the symptoms of Mucopolysaccharidosis type IIIC ?
Answer: What are the signs and symptoms of Mucopolysaccharidosis type IIIC? The Human Phenotype Ontology provides the following list of signs and symptoms for Mucopolysaccharidosis type IIIC. If the information is available, the table below includes how often the symptom is seen in people with this condition. You can use the MedlinePlus Medical Dictionary to look up the definitions for these medical terms. Signs and Symptoms Approximate number of patients (when available) Coarse hair 90% Cognitive impairment 90% Hypertrichosis 90% Malabsorption 90% Mucopolysacchariduria 90% Otitis media 90% Sleep disturbance 90% Abnormal form of the vertebral bodies 50% Abnormality of the clavicle 50% Abnormality of the hip bone 50% Abnormality of the ribs 50% Cataract 50% Craniofacial hyperostosis 50% Developmental regression 50% Genu valgum 50% Hearing impairment 50% Hypertonia 50% Incoordination 50% Limitation of joint mobility 50% Myopia 50% Opacification of the corneal stroma 50% Scoliosis 50% Seizures 50% Umbilical hernia 50% Vocal cord paresis 50% Hepatomegaly 7.5% Splenomegaly 7.5% Asymmetric septal hypertrophy - Autosomal recessive inheritance - Cellular metachromasia - Coarse facial features - Dense calvaria - Diarrhea - Dolichocephaly - Dysostosis multiplex - Dysphagia - Growth abnormality - Heparan sulfate excretion in urine - Hernia - Hirsutism - Hyperactivity - Intellectual disability - Joint stiffness - Kyphoscoliosis - Loss of speech - Motor delay - Motor deterioration - Ovoid thoracolumbar vertebrae - Recurrent upper respiratory tract infections - Rod-cone dystrophy - Synophrys - Thickened ribs - Variable expressivity - The Human Phenotype Ontology (HPO) has collected information on how often a sign or symptom occurs in a condition. Much of this information comes from Orphanet, a European rare disease database. The frequency of a sign or symptom is usually listed as a rough estimate of the percentage of patients who have that feature. The frequency may also be listed as a fraction. The first number of the fraction is how many people had the symptom, and the second number is the total number of people who were examined in one study. For example, a frequency of 25/25 means that in a study of 25 people all patients were found to have that symptom. Because these frequencies are based on a specific study, the fractions may be different if another group of patients are examined. Sometimes, no information on frequency is available. In these cases, the sign or symptom may be rare or common.
Source: GARD