What is Mucopolysaccharidosis, Type IIIB(MPS3B)?
It is a subtype of Mucopolysaccharidosis, Type III. There are four subtypes of this form of the syndrome. Known as a form of childhood dementia the syndrome causes brain damage that is eventually fatal.
Type B is the second most common subtype, after Type A. Except in some Southern European countries where it is the most common subtype.
This syndrome is also known as:
Mps IIIB; MPSIII; Mucopolysaccharidosis III; Mucopolysaccharidosis type III; N-acetyl-alpha-d-glucosaminidase Deficiency; NAGLU Deficiency; Sanfilippo Syndrome B
What gene changes cause Mucopolysaccharidosis, Type IIIB (MPS3B)?
Changes in the NAGLU gene are responsible for causing the syndrome. It is inherited in an autosomal recessive manner.
Autosomal recessive inheritance means an affected individual receives one copy of a mutated gene from each of their parents, giving them two copies of a mutated gene. Parents, who carry only one copy of the gene mutation will not generally show any symptoms but have a 25% chance of passing the copies of the gene mutations onto each of their children.
What are the main symptoms of Mucopolysaccharidosis, Type IIIB (MPS3B)?
Symptoms of the syndrome do not usually present at birth. One of the first symptoms recognised is developmental delay which is usually identified in early childhood and before the age of 6. From this age the symptoms become more severe, and intellectual ability starts to decline. Behavioral issues, including hyperactivity, are also a major symptom and often one of the first identified. Sleeping issues are also common. Affected individuals will also experience speech delay which gets progressively worse with age.
Physical features of the syndrome include coarse hair, excessive hair growth, coarse facial features, and hearing and vision loss. Enlarged organs such as the liver and/or spleen and hernias are also features of the syndrome.
Life expectancy can be varied, ranging from childhood, to early adolescence or early adulthood
Possible clinical traits/features:
Hyperactivity, Hirsutism, Hearing impairment, Hepatomegaly, Heparan sulfate excretion in urine, Joint stiffness, Intellectual disability, Seizure, Thickened ribs, Autosomal recessive inheritance, Ovoid thoracolumbar vertebrae, Synophrys, Progressive neurologic deterioration, Sleep disturbance, Recurrent upper respiratory tract infections, Splenomegaly, Juvenile onset, Dense calvaria, Coarse hair, Coarse facial features, Diarrhea, Dysostosis multiplex, Asymmetric septal hypertrophy, Aggressive behavior, Cardiomegaly.
How is it diagnosed?
To find out if someone has a diagnosis of Mucopolysaccharidosis, Type IIIB, it is important to have a consultation and evaluation with a clinical genetic specialist. Specialists may also suggest specific genetic testing or other types of tests to help reach a diagnosis. FDNA’s AI technology can help speed up the diagnostic process by analyzing facial features and other health information.
