Definition:
Mucolipidosis IIIC is also known as variant pseudo-Hurler polydystrophy and results from mutations in the N-Acelylglucosamine-1-phosphotransferase (GlcNAc-phosphotransferase) y-subunit gene. This enzyme attaches the appropriate targeting signal to lysosomal enzymes. Because of its deficiency multiple lysosomal enzymes are deficient in the lysosome, leading to the accumulation of many classes of large molecules.

Symptoms:
Symptoms for Mucolipidosis IIIC begin in childhood and can vary considerably. This disorder is characterized by metabolic bone disease in which more bone is broken down than being built. This results in brittle bones and mobility difficulties for individuals afflicted with this disorder. Some individuals with Mucolipidosis IIIC may show mobility problems as early as four or five years of age, others at 10 years of age.

Symptoms for Mucolipidosis IIIC include carpal tunnel syndrome, dental complications, enlarged gums, stunted growth, corneal clouding and ear infections. Learning disabilities may be present but many individuals with Mucolipidosis IIIC have a normal intelligence. Orthopedic complications like scoliosis, claw-hands, short stature, stiff and painful joints, and other skeletal abnormalities are also present.

Inheritance Pattern:
Mucolipidosis IIIC is an autosomal recessive disorder.

Life Expectancy:
Many individuals with Mucolipidosis IIIC disease live into adulthood.

Diagnosis and Testing:
An enzyme assay, which measures the amount of N-Acetylglucosamine-1-phosphotransferase, typically confirms a diagnosis. White blood cells are examined to measure the amount of this enzyme. If they measure low in comparison to normal levels, a diagnosis can be made. A skin biopsy for this disorder measures the same enzyme in a cultured tissue sample. Low levels of N-Acetylglucosamine-1-phosphotransferase, in comparison to the normal standards may confirm a diagnosis.

The gene responsible for this disorder has been identified, rendering accurate diagnosis, prenatal diagnosis and carrier testing possible.

Treatment:
There is no cure for Mucolipidosis IIIC. Treatment is limited to controlling or reducing symptoms associated with this disorder. Physio-therapy, particularly hydrotherapy, has proven effective at relieving muscle stiffness and to increase affected individual’s mobility. Crutches, a wheelchair or scooters are treatment options as this metabolic bone disease progresses. Inserting rods in the spine to stabilize the vulnerable areas can treat scoliosis.

Patient Groups:
International Society for Mannosidosis & Related Diseases
P.O. Box 328
Dexter, MI 48130
www.mannosidosis.org
tel: (734) 449-8222
fax: (734) 449-2282
Terri Klein, Executive Director
info@ismrd.org

Patient Groups:
National MPS Society
4220 NC Highway 55, Suite 140
Durham NC, 27713
www.mpssociety.org
tel: (919) 806-0101
fax: (919) 806-2005
Barbara Wedehase, Executive Director
info@mpssociety.org