Definition:
Pseudo-Hurler Polydystrophy/Mucolipidosis IIIA is caused by the lack of a number of enzymes which, although present in the cell, lack a signal needed to transport them inside the lysosome. The enzyme responsible for giving the targeting signal to the enzymes to enter into the lysosome, is called N-Acetylglucosamine-1-phosphotransferase. It is this enzyme that malfunctions in individuals afflicted with Pseudo-Hurler Polydystrophy/Mucolipidosis IIIA. Lipids, proteins and carbohydrates inside the lysosome need to be metabolized via enzymes.  Without the proper functioning of N-acetylglucosamine-1-phototransferase, a build up of these substances occurs because enzymes are unable to travel inside of the lysosome. These substances accumulate into masses referred to as inclusion bodies inside the lysosome.

This disorder is called Pseudo-Hurler because it resembles a mild form of Hurler disease, one of the mucopolysaccharide (MPS) diseases.

Symptoms:
The symptoms of Pseudo-Hurler Polydystrophy/Mucolipidosis IIIA include mild enlargement of organs, skeletal deformities, carpal tunnel syndrome, aortic valve disease and corneal clouding.

Inheritance Pattern:
Pseudo-Hurler Polydystrophy/Mucolipidosis IIIA is an autosomal recessive disorder.

Life Expectancy:
Some children with severe forms of this disease do not live beyond childhood. However, there is a great variability among patients, hence many can live into adulthood.

Diagnosis and Testing:
An enzyme assay, measuring the amount of N-acetylglucosamine-1-phototransferase, can confirm a diagnosis. White blood cells are examined to measure the amount of this enzyme. Amounts of the enzyme found to be low in comparison to normal standards for N-acetylglucosamine-1-phototransferase may result in a diagnosis of this disorder. A skin biopsy measures the same enzyme in a cultured tissue sample. Low levels of N-acetylglucosamine-1-phototransferase in comparison to the normal standards may confirm a diagnosis.

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

Treatment:
There is no cure for Pseudo-Hurler Polydystrophy/Mucolipidosis IIIA. Treatment is limited to controlling or reducing symptoms associated with this disorder. Physio-therapy, particularly hydrotherapy has proven effective at relieving muscle stiffness and increasing mobility. The use of crutches, a wheelchair or scooters are treatment options as the metabolic bone disease progresses. The insertion of rods in the spine to stabilize the vulnerable areas can treat scoliosis. Heart valve replacement surgery may be necessary as this disorder progresses.