Diagnosing NP-C is complicated and the highly varied pattern of symptoms combined with the rarity of the disease means it is often misdiagnosed or goes undetected. Consequently, the true incidence of NP-C is likely to be underestimated. Despite this, it is still possible to make a definite diagnosis of NP-C using current techniques, listed below. New diagnostic techniques are currently being developed that will make it easier to diagnose NP-C.
1. Biochemical testing
Fibroblasts cultured from a skin biopsy are used to conduct:
- Cholesterol transport tests: cholesterol esterification
- Cholesterol storage tests: filipin staining detects lipid accumulation
2. Histological analyses
- Foam cells in bone marrow and the spleen
- Sea-blue histiocytes in bone marrow
- Polymorphous cytoplasmic bodies in skin, rectal neurons, liver or brain
3. Genetic testing
Not used to make a primary diagnosis, but to:
- Confirm a diagnosis of the variant biochemical phenotype
- Make a prenatal diagnosis
- Identify heterozygotes in probands’ families
4. Imaging
Magnetic resonance imaging (MRI), computed tomography (CT) or proton magnetic resonance spectroscopy (PET) is used to detect cerebral atrophy
