Investigations

On testing there are lipo-pigments in the urine and lymphocytes.

Rectal biopsy should reveal lipofuscin storage - this is positive on PAS staining.

• For CLN1, palmitoyl protein thioesterase (PPT) levels can be measured in leukocytes, cultured fibroblasts, dried blood spots, and saliva. Lymphoblast PPT is less than 0.2 pmols/min/mg (normal levels are 1 to 3). (1)
• For CLN2, tripeptidyl peptidase 1 (TTP1) levels can be measured in leukocytes, cultured fibroblasts, dried blood spots, and saliva. Fibroblast TTP1 activity is approximately 17,000 micromoles of amino acids produced per hour per milligram of protein. The TTP1 activity in CLN2 NCL is less than 4% of normal levels. (2)
• Magnetic resonance imaging (MRI) & MR Spectroscopy- NCL shows predominant cerebellar-over-cerebral atrophy in CLN2, CLN5, and CLN7 diseases and minimal abnormality until early adolescence in CLN3 disease. (3)

References

1. Kohan R et al. Palmitoyl Protein Thioesterase1 (PPT1) and Tripeptidyl Peptidase-I (TPP-I) are expressed in the human saliva. A reliable and non-invasive source for the diagnosis of infantile (CLN1) and late infantile (CLN2) neuronal ceroid lipofuscinoses. Clin Biochem. 2005 May;38(5):492-4
2. Chang X et al. Clinical study in Chinese patients with late-infantile form neuronal ceroid lipofuscinoses. Brain Dev. 2012 Oct;34(9):739-45
3. Biswas A et al. Expanding the Neuroimaging Phenotype of Neuronal Ceroid Lipofuscinoses. AJNR Am J Neuroradiol. 2020 Oct;41(10):1930-1936.