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Test ID: TPPTL Tripeptidyl Peptidase 1 and Palmitoyl-Protein Thioesterase 1, Leukocytes

Reporting Name

TPP1 and PPT1, WBC

Useful For

Evaluation of patients with clinical presentations suggestive of neuronal ceroid lipofuscinoses (NCL)


Aids in the differential diagnosis of infantile and late infantile NCL


This test is not useful for detecting carrier status of NCL.

Specimen Type

Whole Blood ACD

Shipping Instructions

For optimal isolation of leukocytes, it is recommended the specimen arrive refrigerated within 6 days of collection to be stabilized. Collect specimen Monday through Thursday only and not the day before a holiday. Specimen should be collected and packaged as close to shipping time as possible.

Specimen Required


Preferred: Yellow top (ACD solution B)

Acceptable: Yellow top (ACD solution A)

Specimen Volume: 6 mL

Collection Instructions: Send specimen in original tube. Do not aliquot.

Specimen Minimum Volume

5 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Whole Blood ACD Refrigerated (preferred) 6 days YELLOW TOP/ACD
  Ambient  6 days YELLOW TOP/ACD

Reference Values


85-326 nmol/hour/mg protein



20-93 nmol/hour/mg protein

Day(s) Performed

Preanalytical processing: Monday through Saturday.

Assay performed: Twice per month

Test Classification

This test was developed, and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
TPPTL TPP1 and PPT1, WBC 93704-5


Result ID Test Result Name Result LOINC Value
50688 Specimen 31208-2
50689 Specimen ID 57723-9
50690 Source 31208-2
50691 Order Date 82785-7
50692 Reason for Referral 42349-1
50693 Method 85069-3
50694 TPP1L 76038-9
50695 PPT1L 74935-8
50696 Interpretation 59462-2
50697 Amendment 48767-8
50698 Reviewed By 18771-6
50699 Release Date 82772-5

Clinical Information

The neuronal ceroid lipofuscinoses (NCL) comprise a group of recessively inherited neurodegenerative disorders involved in lysosomal protein catabolism. They are considered the most common of the neurogenetic storage disorders, with incidences ranging from 1.3 to 7 per 100,000 live births. Clinically, they are characterized by vision loss, seizures, mental regression, behavioral changes, movement disorders, and the accumulation of autofluorescent storage material in the brain and tissues. Although at least 12 different genes have been identified, the NCL have traditionally been categorized based on the age of onset of symptoms: infantile, late-infantile, juvenile, and adult. Infantile and late-infantile NCL are caused primarily by defects in PPT1 and TPP1, respectively. Tissue damage is selective for the nervous system and many patients die in the first decade of life due to central nervous system degeneration.


Children affected by infantile NCL (CLN1) typically have normal growth and development until about 6 to 12 months of age. Slowed head growth occurs at around 9 months followed by psychomotor degeneration, seizures, and progressive macular degeneration leading to blindness by the age 2 years. CLN1 is caused by a deficiency of the lysosomal enzyme palmitoyl-protein thioesterase 1 (PPT1), which cleaves long-chain fatty acids (usually palmitate) from cysteine residues. Electron microscopy shows granular osmophilic deposits in most cell types. PPT1 is thought to play an active role in various cell processes including apoptosis, endocytosis, and lipid metabolism. Infantile NCL has an incidence of 1 in 20,000 in Finland and is rare elsewhere.


The late infantile form of NCL (CLN2) is primarily caused by deficiency of the lysosomal enzyme tripeptidyl peptidase 1 (TPP1), which cleaves tripeptides from the N-terminus of polypeptides. Tissue damage results from the defective degradation and consequent accumulation of storage material with a curvilinear profile by electron microscopy. There is widespread loss of neuronal tissue especially in the cerebellum and hippocampal region. Disease onset occurs at 2 to 4 years of age with seizures, ataxia, myoclonus, psychomotor retardation, vision loss, and speech impairment.


Diagnostic strategy depends on the age of onset of symptoms. In children presenting between the ages 0 to 4 years, enzyme assay of PPT1 and TPP1 is an appropriate first step. For other patients suspected of having an NCL, the molecular genetic test is available; see NCLGP / Neuronal Ceroid Lipofuscinosis (Batten Disease) Gene Panel, Varies.


Tripeptidyl peptidase 1 (TPP1) enzyme activity or palmitoyl-protein thioesterase 1 (PPT1) enzyme activity below 5 nmol/hour/mg of protein is highly suggestive of late-infantile and infantile neuronal ceroid lipofuscinoses (NCL), respectively.

Clinical Reference

1. Mole S, Cotman S: Genetics of the neuronal ceroid lipofuscinoses (Batten disease). Biochem et Biophys Acta. 2015 Oct;1852:2237-2241

2. Kavianen R, Eriksson K, Losekoot M, et al: Juvenile-onset neuronal ceroid lipofuscinosis with infantile CLN1 mutation and palmitoyl-protein thioesterase deficiency. Eur J Neurol. 2007 Apr;14(4):369-372

3.Giugliani R, Vairo F, Beck M, et al: Lysosomal disorders. In: Sarafoglou K, Hoffman GF, Roth KS, eds. Pediatric Endocrinology and Inborn Errors of Metabolism. 2nd ed. McGraw-Hill Medical Division; 2017:983-1021

4. Nita DA, Mole SE, Minassian BA: Neuronal ceroid lipofuscinoses. Epileptic Disord. 2016 Sep 1;18(S2):73-88. doi: 10.1684/epd.2016.0844

5. Williams RE, Adams HR, Blohm M, et al: Management strategies for CLN2 disease. Pediatr Neurol. 2017 Apr;69:102-112. doi: 10.1016/j.pediatrneurol.2017.01.034

6. Mole SE, Anderson G, Band HA, et al: Clinical challenges and future therapeutic approaches for neuronal ceroid lipofuscinosis. Lancet Neurol. 2019 Jan;18(1):107-116. doi: 10.1016/S1474-4422(18)30368-5

Report Available

8 to 15 days

Method Name



1. New York Clients-Informed consent is required. Document on the request form or electronic order that a copy is on file. The following documents are available in Special Instructions:

-Informed Consent for Genetic Testing (T576)

-Informed Consent for Genetic Testing-Spanish (T826)

2. Biochemical Genetics Patient Information (T602) in Special Instructions

3. If not ordering electronically, complete, print, and send a Biochemical Genetics Test Request (T798) with the specimen.

Mayo Clinic Laboratories | Genetics and Pharmacogenomics Catalog Additional Information: