Role of skin punch biopsy in diagnosis of small fiber neuropathy-A review for the neuropathologist

Over the last three decades, skin punch biopsy has become the gold standard for diagnosis of small fiber neuropathies, including autonomic neuropathies commonly seen in diabetics, patients with HIV, and children with hereditary sensory autonomic neuropathies and toxin-induced neuropathy. Clinical, biochemical, electrophysiological tests are inconclusive, making it difficult to diagnose and initiate treatment. A skin punch biopsy is easy to perform in the outpatient clinic, is highly sensitive, and provides an objective diagnosis. Importantly, it helps avoid performing invasive nerve biopsy in patients with small fiber neuropathy, thereby preventing complications such as non-healing of the biopsy site, which is common in these patients. Secondly, the greatest advantage of skin punch biopsies is that they can be repeated any number of times, unlike a nerve biopsy, and are useful to evaluate disease progression and therapeutic response. More recently, its use has been expanded to the diagnosis of large fiber neuropathies, inherited demyelinating neuropathies, etc., obviating the need for a nerve biopsy. The European Federation of Neurological Societies has published guidelines for evaluation to ensure uniformity with regard to the site of biopsy, processing, and quantification. The evaluation of the skin biopsy involves morphometric assessment of the intraepidermal nerve fiber density using PGP 9.5 immunostained sections by bright-field microscopy. This review focuses on the practical aspects of skin punch biopsy and its utility for the practicing pathologist.

Tissue-Clearing Technique and Cutaneous Nerve Biopsies: Quantification of the Intraepidermal Nerve-Fiber Density Using Active Clarity Technique-Pressure Related Efficient and Stable Transfer of Macromolecules Into Organs

BACKGROUND AND PURPOSE: Cutaneous nerve biopsies based on two-dimensional analysis have been regarded as a creditable assessment tool for diagnosing peripheral neuropathies. However, advancements in methodological imaging are required for the analysis of intact structures of peripheral nerve fibers. A tissue-clearing and labeling technique facilitates three-dimensional imaging of internal structures in unsectioned, whole biological tissues without excessive time or labor costs. We sought to establish whether a tissue-clearing and labeling technique could be used for the diagnostic evaluation of peripheral neuropathies. METHODS: Five healthy individuals and four patients with small-fiber neuropathy (SFN) and postherpetic neuralgia (PHN) were prospectively enrolled. The conventional methods of indirect immunofluorescence (IF) and bright-field immunohistochemistry (IHC) were adopted in addition to the tissue-clearing and labeling method called active clarity technique-pressure related efficient and stable transfer of macromolecules into organs (ACT-PRESTO) to quantify the intraepidermal nerve-fiber density (IENFD). RESULTS: The mean IENFD values obtained by IF, bright-field IHC, and ACT-PRESTO in the healthy control group were 6.54, 6.44, and 90.19 fibers/mm², respectively; the corresponding values in the patients with SFN were 1.99, 2.32, and 48.12 fibers/mm², respectively, and 3.06, 2.87, and 47.21 fibers/mm², respectively, in the patients with PHN. CONCLUSIONS: This study has shown that a tissue-clearing method provided not only rapid and highly reproducible three-dimensional images of cutaneous nerve fibers but also yielded reliable quantitative IENFD data. Quantification of the IENFD using a tissue-clearing and labeling technique is a promising way to improve conventional cutaneous nerve biopsies.

Skin Biopsy: Emerging Method for Small Nerve Fiber Evaluation / 대한임상신경생리학회지

Skin biopsy with investigation of small nerve fiber in human epidermis and dermis has been proven to be a useful method for demonstration of small fiber neuropathy. Quantification of intraepidermal nerve fiber density using anti-Protein Gene Product 9.5 (PGP 9.5) antibody is standardized method to diagnose the small fiber neuropathy. Skin biopsy method also makes it possible to differentiate the type of nerve fibers by using different antibodies. Quantification of dermal structures with different type of nerve fibers could be used to invest pathophysiologic mechanism of diseased state.

Assessment of Intraepidermal Nerve Fiber using Skin Biopsy in Diabetic Polyneuropathy

BACKGROUND: Immunohistochemical staining of skin for panaxonal marker, protein gene product 9.5 (PGP 9.5), has recently emerged as a useful diagnostic procedure for the assessment of small nerve fibers. The first aim of our study is to quantify the intraepidermal nerve fibers (IEDNF) and to investigate the histological changes of IEDNF in diabetic patents. And the second is to evaluate whether IEDNF has the correlation with the clinical, electrophysiological and biological parameters. METHODS: Skin biopsy specimens were obtained at the distal leg and proximal thigh from twelve type 2 diabetes mellitus patients having the symptoms of peripheral polyneuropathy. Fixed sections were stained using PGP 9.5, and the number of intraepidermal nerve fibers at each site was compared with those of fifteen normal healthy volunteers. We analyzed the correlation of IEDNF density with the clinical history, neuropathic symptom score (NSS), severity of diabetes (serum glucose, HbA1C), and nerve conduction studies. RESULTS: The number of IEDNF in diabetic patients was 3.0 per millimeter at the distal leg and 12.7 per millimeter at the proximal thigh compared with 15.3 per millimeter and 23.3 per millimeter in normal control respectively. Some specimen showed a morphological change of axons such as axonal swelling. The IEDNF density was not correlated with the duration of disease, biological or electrophysiological parameters but correlated with the clinical neuropathic symptom score. CONCLUSIONS: The IEDNF density is reduced in all the diabetic patients, more severely at the distal extremity. We suggest skin biopsy can provide the quantification as well as the objective evidence for the small fiber involvement of diabetic neuropathy.