Neuronal Ceroid Lipofuscinosis 2 (CLN2): Tripeptidyl Peptidase 1 Enzyme Analysis

This biochemical test is a quantitative measurement of tripeptidyl peptidase 1 enzyme activity and can be used as a 1st tier test for patients with a clinical suspicion of Neuronal Ceroid Lipofuscinosis Type 2 (CLN2). Demonstration of deficient tripeptidyl peptidase 1 enzyme activity is considered the gold standard to confirm a diagnosis of Neuronal Ceroid Lipofuscinosis Type 2 (CLN2).

In addition, it can be used to clarify molecular findings in the TPP1 gene and to monitor patients undergoing treatment.

Turnaround Time

2 weeks

CPT Code(s)

82657

Cost

$200

Enzymes

• Neuronal Ceroid Lipofuscinosis Type 2 (CLN2)

The neuronal ceroid lipofuscinoses (CLN) are a group of conditions that are inherited in an autosomal recessive pattern. CLN1 is characterized by progressive microcephaly, contractures, developmental delay, psychiatric symptoms, and neurological degeneration including seizures and ataxia. Retinal and macular degeneration leads to blindness by the age of 2 years with diminished or abolished ERG results. Age of onset varies with infantile, late-infantile, juvenile and adult-onset forms of the disease with younger ages of onset typically associated with a more rapid progression of symptoms. The intracellular accumulation of lipopigments results in a characteristic microscopic pattern called granular osmiophilic deposits (GROD).

This test can be used to confirm a suspected neuronal ceroid lipofuscinosis 2 (CLN2) diagnosis.

LC-MS/MS

Enzyme activity is measured in dried blood spots. A minimum of three circles need to be filled in. Each circle should contain one drop of blood (about 100 microliters). A whole blood sample (3-5 ml) in a green top, sodium heparin tube can also be submitted for this test. The laboratory will create a DBS card from the tube of blood when the specimen arrives.

For a dried blood spot: When the sample has dried 3-4 hours, fold cover at score line, over sample, and tuck into flap. Whole blood samples should be sent at ambient temperature and must arrive to the laboratory the next day.