Intraepidermal nerve fiber density as a marker of early diabetic neuropathy

The purpose of the study was to reliably identify an early stage of diabetic polyneuropathy (DPN) by measuring injury to epidermal nerve fibers. We compared intraepidermal nerve fiber density (IENFD) at the ankle and thigh of 29 diabetic subjects who had no clinical or electrophysiological evidence of small- or large-fiber neuropathy to that of 84 healthy controls. The mean ankle IENFD of diabetic subjects was 9.1+/-5.0 mm and that of controls, 13.0+/-4.8 mm (P<0.001). The thigh IENFD did not differ significantly. The IENFD ratio (thigh IENFD divided by ankle IENFD) was 2.39+/-1.30 in diabetic subjects and 1.77+/-0.58 in controls (P<0.001), indicating a length-dependent reduction of IENFD in diabetics. Ankle IENFD remained significantly lower and the IENFD ratio higher in diabetic subjects after adjusting for age. Two subjects had parasympathetic dysfunction, two had retinopathy, and two early nephropathy. Age, height, weight, duration of diabetes, and average HbA1c did not influence IENFD among diabetic subjects. We used receiver operating characteristic (ROC) curves to describe and compare the utility of various threshold values of ankle IENFD and IENFD ratio for the diagnosis of early DPN. The sensitivity and specificity of diagnosing DPN using ankle IENFD of less than 10 mm were 72.4% and 76.2%, respectively. Thus, asymptomatic diabetics have a measurable, length-dependent reduction of distal epidermal nerves. Analogous to microalbuminuria in diabetic nephropathy, reliable identification and quantitation of nascent diabetic neuropathy may have potential therapeutic implications.     

Enzyme replacement therapy and intraepidermal innervation density in Fabry disease

We prospectively evaluated the effect of enzyme replacement therapy (ERT) on the intraepidermal nerve fiber density (IENFD) and thermal threshold in patients with Fabry disease, an X-linked disorder associated with a painful small-fiber neuropathy and decreased linear IENFD in a length-dependent pattern. Twenty-five hemizygous male patients with Fabry disease were enrolled in a 6-month, randomized, placebo-controlled ERT trial of 0.2 mg/kg of alpha-galactosidase A (agalsidase-alfa) every 2 weeks followed by an additional 12 months of open-label ERT for both populations. IENFD and thermal threshold were measured in the distal thigh at baseline, 6 months, and 18 months from initiation of the trial. We found no significant difference in IENFD between the treatment groups at 6 months. After an additional year of ERT, there was a significant reduction in IENFD in the patient group as a whole, attributable to the declining glomerular filtration rate. Thermal thresholds remained unchanged. We conclude that epidermal nerve fiber regeneration, as measured in the distal thigh, does not occur in this patient population after 12-18 months of ERT.     

健康皮肤标本表皮神经纤维密度研究

目的 探讨健康皮肤标本表皮神经纤维密度的参考值范围,并分析年龄、解剖部位以及种族对表皮神经分布的影响.方法 对70例皮肤标本进行皮肤神经活体组织检查.标本经10%福尔马林常规固定后切成10μm厚石蜡切片,以PGP9.5为特异性轴突标记物进行免疫组织化学染色.观察皮肤神经纤维的形态学特点,并测定表皮神经纤维密度,进行统计学分析.结果 不同年龄组小腿远端及腕部表皮神经纤维密度差异无统计学意义,但随年龄增加,各部位表皮神经分布有减少的趋势.上臂(91.8±21.1)、大腿近端(89.2±21.4)的表皮神经分布较腕部(64.5±22.5)、小腿远端(62.9±15.3)密集.健康人小腿远端的表皮神经纤维密度正常参考值范围>40.6纤维/m2.结论 通过皮肤活体组织检查技术可清晰显示神经纤维形态,便于对表皮神经纤维进行定量研究,为周围神经病的诊断和研究提供了一个可靠的平台.     

Epidermal nerve fiber density in sensory ganglionopathies: clinical and neurophysiologic correlations.

We assessed the involvement of somatic unmyelinated fibers in sensory ganglionopathies by skin biopsy and quantitative sensory testing (QST). Sixteen patients with ganglionopathy, 16 with axonal neuropathy, and 15 normal controls underwent skin biopsy at the proximal thigh and the distal leg. Intraepidermal nerve fibers (IENF) were immunostained by antiprotein gene product 9.5, and their linear density was quantified under light microscopy. Confocal microscopy studies with double staining of nerve fibers and basement membrane were also performed. Healthy subjects and neuropathy patients showed the typical proximodistal gradient of IENF density; in neuropathies, values were significantly lower at the distal site of the leg, confirming the length-dependent loss of cutaneous innervation. Conversely, ganglionopathy patients with hyperalgesic symptoms did not show any change of IENF density between the proximal thigh and the distal leg. The distinct pattern of epidermal denervation seen in sensory ganglionopathy reflected the degeneration of somatic unmyelinated fibers in a fashion that was not length-dependent, which was consistent with both clinical and neurophysiologic observations and supported the diagnosis.     

Axonal fluorescence quantitation provides a new approach to assess cutaneous innervation

We present a novel approach to quantify skin innervation by measuring the PGP 9.5 immunoreactive (PGP-ir) fluorescence corresponding to axons within the epidermis and dermis. The skin biopsies from 35 controls and 45 small fiber neuropathy (SFN) patients were included. In 50-μm free-floating sections, we determined the intraepidermal nerve fiber density (IENFD) by direct fluorescence visualization and captured 2-μm thick individual optical sections using the same confocal microscope and magnification. We measured the fluorescence of the PGP-ir axons in both, epidermal and dermal area by using the ImageJ software. There was good interobserver and intraobserver reliability of PGP-ir measures, similar than for IENFD. The PGP-ir axons were found decreased in patients with SFN (1.1‰ and 9.0‰ respectively for epidermal and dermal area in contrast to 2.2‰ and 16.0‰, respectively to controls). The area under the ROC curve was 0.90 for the IENFD, 0.84 for epidermal PGP-ir axons and 0.70 for dermal PGP-ir axons. There was a positive correlation between the IENFD and the PGP-ir axons at epidermis (Spearman Rho=0.66, p<0.001) as well as for the dermal nerve length and the PGP-ir axons at dermis (Spearman Rho=0.45, p<0.05). This method is also particularly adequate for the quantitation of dermal nerve fibers. We conclude that quantifying the fluorescent PGP-ir axons could help to assess skin innervation (dermal and epidermal nerve fibers) in patients with SFN.     

皮肤神经活体组织检查在周围神经病诊断中的应用

目的 探讨皮肤神经活体组织检查在周围神经病诊断中的作用,建立正常参考值范围,并比较临床表现、神经电生理检查与表皮神经纤维病变的一致性.方法 对51例有周围神经病症状和(或)体征的患者进行皮肤神经活体组织检查,计算表皮神经纤维密度(IENFD);同时收集10名健康志愿者作为对照.51例患者中,41例行常规肌电图及神经传导速度(NCV)检查.21例行皮肤交感反射(SSR),比较IENFD与NCV及SSR的一致性.结果 对照组与病例组相比,大腿IENFD(根/mm)分别为21.4±2.7及15.0±6.3(t=2.976,P=0.004);小腿IENFD分别为15.4±2.2及8.1±5.9(t=3.191,P=0.002).病例组与对照组相比大、小腿IENFD均有减少,差异有统计学意义.51例患者中,皮肤神经活体组织检查异常48例(94.1%),其中33例表现为长度依赖性周围神经病变;41例行常规肌电图检查,21例异常(51.2%);21例行SSR检查,异常17例(81.0%).仅表现为小纤维病变症状和(或)体征的29例患者中,27例(93.1%)皮肤神经活体组织检查异常;其中20例行NCV,异常6例(30.0%);14例行SSR,11例异常.结论 皮肤神经活体组织检查操作简单安全,对于以小神经纤维受累为主的周围神经病皮肤神经活体组织检查有较高的灵敏度.     

Intraepidermal nerve fiber density of healthy human

Abstract

Objectives:

To analyze intraepidermal nerve fiber density (IEFND) by skin biopsy, evaluate the effect of age, anatomical sites, and ethnic origin on IEFND and develop a reference range of IENFD at the distal leg of healthy human.

Methods:

Seventy skin biopsy specimens from surgical procedures involving 70 patients were analyzed. Specimens were fixed routinely in formalin and thereafter embedded in paraffin. Nerve fibers of 10-μm-thick sections were observed using immunoperoxidase staining with panaxonal antibody protein gene product 9·5 (PGP 9·5). The morphology of intraepidermal nerve fibers (IENFs) and the IENFD was determined using light microscope. The statistical analysis was performed with SPSS 16·0 software.

Results:

No significant correlation was observed between IENFD and age (P_wrist = 0·830, P_{distal leg} = 0·478). The significant correlation was observed between IENFD and anatomic site (P = 0·001), the IENFD of upper arm and proximal thigh were significantly higher than that of wrist and distal leg. The reference range for IENFD of distal leg in normal Chinese humans was 40·55 fibers/mm². The IEFND of Chinese healthy human was significantly lower than that of Finnish (62·87 ± 15·25 vs 114·617 ± 32·322 fibers/mm², P < 0·05).

Discussion:

Skin biopsy may be a useful tool in sensory neuropathies. IENFD is independent of age, but varies in different parts of the body. The proximal sites have a higher IENFD, but no significant difference is found between the wrist and distal leg.     

Skin biopsy in assessing meralgia paresthetica

Introduction: Meralgia paresthetica is a focal neuropathy caused by compression of the lateral femoral cutaneous nerve (LFCN). The disease can be difficult to assess by neurophysiological or imaging studies. Methods: We studied 5 patients who presented to our neuromuscular clinic from April 2012 to December 2014 with a clinical suspicion of meralgia paresthetica and had skin biopsies with intraepidermal nerve fiber density (IENFD) evaluation. Results: The mean age at onset was 37.2 (range 21–59) years. There were 4 women and 1 man. Two were obese, 2 wore tight jeans, and 1 had mild diabetes mellitus. IENFD was reduced in the symptomatic proximal thigh in all 5 patients and was also reduced in the asymptomatic thigh in 2 patients. It was normal in the distal leg in 4 patients. Conclusion: Meralgia paresthetica is associated with loss of small intraepidermal nerve fibers. Skin biopsy with IENFD evaluation may be a useful diagnostic tool for this disease. Muscle Nerve 53 : 641–643, 2016     

Quantitative analysis of epidermal innervation in Fabry disease

OBJECTIVE: To use skin biopsy specimens to quantitate the cutaneous innervation density of Fabry patients who had preserved renal function. BACKGROUND: The small fiber neuropathy of Fabry disease is difficult to detect and quantitate by conventional methods. Because this neuropathy is a common characteristic of Fabry disease, quantitating changes in this parameter would be helpful in demonstrating the effectiveness of enzyme or gene replacement therapy. METHODS: Patients underwent skin biopsy at the thigh and foot. Innervation density was determined by counting free nerve endings in the epidermis. These data were compared with nerve conduction studies, and in selected patients, fiber quantitation of sural nerve biopsy specimens. RESULTS: The Fabry patients had normal results of nerve conduction studies and large fiber quantitation by sural nerve biopsy. However, the involvement of small cutaneous fibers in these patients was easily demonstrable and quantifiable by skin biopsy. All patients showed severe loss of intraepidermal innervation at the ankle, but fiber loss at the distal thigh was proportionately less severe. CONCLUSIONS: The nerve damage in Fabry patients with preserved renal function involves exclusively small myelinated and unmyelinated fibers, and skin biopsy is a useful in detecting and quantitating such damage. Comparison of cutaneous innervation density with quantitation of sural nerve biopsy specimens demonstrated that skin biopsy specimens were as sensitive in detecting the presence of neuropathy as were the nerve specimens. It is speculated that analysis of cutaneous innervation may provide a useful marker of the nervous system's response to specific therapy for Fabry disease.     

Signs of sympathetic and endothelial cell activation in the skin of patients with restless legs syndrome

ObjectivesTo evaluate skin biopsies of patients with early- and late onset restless legs syndrome (RLS) for concomitant small fiber neuropathy (SFN) and to determine cutaneous sympathetic innervation and microvascularization in comparison to healthy individuals.MethodsDensity of intraepidermal nerve fibers (IENFD), adrenergic nerve fibers and dermal capillaries was analyzed by immunofluorescence for PGP9.5, tyrosine hydroxylase and endothelial markers CD31 and CD105 in skin biopsies of 11 individuals with RLS and 8 age- and sex-matched controls.ResultsIENFD did not differ between RLS and controls, but two RLS patients with comorbid impaired glucose metabolism fulfilled morphometric criteria of SFN according to published normative values. In contrast, dermal nerve bundles of RLS patients showed an increased density of tyrosine hydroxylase⁺ adrenergic nerve fibers (p < 0.005). Moreover, an increased ratio between immature CD105⁺ and mature CD31⁺ endothelial cells within dermal capillaries was observed in RLS (p < 0.02).ConclusionsSFN, as a potential contributing factor for RLS, should be considered in patients with predisposing comorbidities presenting with burning or shooting pain, dysesthesias and impaired sensory and temperature perception. Evidence of an increased adrenergic innervation of the skin in RLS patients is in accordance with sympathetic hyperactivity while signs of endothelial cell activation may reflect an adaptive response to tissue hypoxia.     

Sural sensory nerve action potential,epidermal nerve fiber density,and quantitative sudomotor axon reflex in the healthy elderly

Introduction: Polyneuropathy evaluation in older patients is often challenging due to conflicting data regarding normative values for peripheral nerve testing. Methods: We characterized the results of sural nerve conduction studies, intraepidermal nerve fiber density (IENFD), and quantitative sudomotor axon reflex testing (QSART) in a prospective study of 50 healthy subjects aged ≥60 years. Results: Of the 50 subjects, 48 (96%) had an obtainable sural sensory nerve action potential (SNAP). Using quantile regression, we estimated the lower limit of normal (LLN) for sural amplitudes to be 3 μV for patients 60–70 years, 1 μV for those 70–74 years, and <1 μV (absent) for those ≥75 years of age. IENFD and QSART volume were reduced with advancing age, although IENFD was lower in men and QSART volume was lower in women. Conclusions: We propose that an absent sural SNAP in patients up to 75 years of age should be considered abnormal. Our findings also support age‐ and gender‐stratified normative data for IENFD and QSART. Muscle Nerve 49:564–569, 2014     

Cutaneous innervation in ross syndrome: a functional and morphological study in 8 patients

Evaluation of epidermal nerve fiber (ENF) density by skin biopsy is nowadays considered as the gold standard for the diagnosis of small fiber neuropathies. ENFs show in normal subjects quite a regular distribution between the keratinocytes while in patients with small fiber neuropathies we can find, besides a loss of ENFs, evident anomalies of their distribution. Different patterns of nerve fiber dispersion can express different pathophysiological processes. The aim of this study was to define a tool capable of describing the distribution of ENF in the epidermis. For this purpose, we measured the distance between subsequent epidermal fibers on skin samples of healthy and diabetic subjects. We calculated the standard deviation of the interfiber length as a parameter (the dispersion index – DI) to evaluate the variability of the distance between consecutive ENFs. We selected thigh skin samples from five healthy subjects (age range 30–50 years) and five age and sex matched diabetic patients. Samples were processed using immunohistochemical techniques. Sections were PGP 9.5 and Collagen IV double stained to show nerve fibers and basement membrane. One randomly selected section for each subject was acquired for its entire length (usually seven 20x confocal images obtained from a z‐stack of 16 two micron optical sections) using a confocal microscope (CARV, Atto Biosciences, Rockville MD, USA). We measured the distance between consecutive ENFs along the entire epidermal length, using dedicated software (ScionImage, Scion Corporation Frederick, Maryland USA). In diabetic patients the DI resulted significantly higher than in normal subjects. We suggest that DI along with the ENF density can be useful to better characterize epidermal innervation.     

Epidermal innervation: changes with aging, topographic location, and in sensory neuropathy.

In previous work we demonstrated little effect of aging on the density and spatial pattern of epidermal innervation, however, this was restricted to two sites proximal and distal in the leg. To expand on these observations, we used punch skin biopsy in ten healthy controls to examine the variation in intra-epidermal nerve fiber (IENF) density at multiple specific sites in the leg. There was a consistent gradient in IENF from proximal to distal sites in all subjects, but minimal effect of age was noted. In the older age group (> or =70 years), the IENF densities ranged from 28.6+/-1.9 IENF/mm at the trunk to 15.5+/-1.5 at the distal leg. In a group of six patients with painful sensory neuropathy, we confirmed a length-dependent reduction in IENF. We observed what may be a predegenerative change, namely increased branching of epidermal nerve fibers at clinically unaffected sites. These data suggest little age-related change in IENF, at least up to age 75 years, in healthy normals. The increased branching complexity noted in unaffected sites in patients with sensory neuropathies implies that this may be a predegenerative change, preceding the actual loss of nerve fibers. Skin biopsy may be a useful tool for assessing the topographic extent and degree of nerve fiber damage in sensory neuropathies and its quantitative interpretation should be little affected by aging changes.     

Epidermal innervation in healthy children and adolescents

Introduction: Epidermal nerve fiber (ENF) density, morphology, and epidermal innervation patterns were examined in children using 2 different techniques, punch biopsy and suction blister. Methods: Healthy children without symptoms or history of peripheral neuropathy and normal by neurologic examination were studied. Punch biopsy and suction blister specimens were collected from the lateral thigh and distal leg. ENFs were traced from confocal images of immunohistochemically stained samples. Statistical methods included repeated‐measures analysis of covariance. Results: Blister and biopsy nerve counts were associated. ENF density in children was dense, lower for older children (P < 0.01) and with no difference between boys and girls (P = 0.92). Many ENFs appeared multibranched and elongated. Conclusions: Epidermal innervation in the pediatric population is dense and age‐dependent. Blister specimens are less invasive and may provide an alternative to punch biopsy for determining ENF density in children at risk for neuropathy. Muscle Nerve 51 : 378–384, 2015     

Small fibers in Fabry disease: baseline and follow-up data under enzyme replacement therapy

Fabry disease (FD) is an X-linked lysosomal storage disorder which may lead to impaired peripheral nerve function, mostly affecting small nerve fibers, and to neuropathic pain. Characteristics of the neuropathy associated with FD and the covariates for its development and temporal course have not been described in a large cohort. We studied small fiber function and morphology in 120 Fabry patients at baseline and in subgroups of these until 4-year follow-up. Baseline neurological (89/120) and electrophysiological (106/120) examination was mostly normal. Quantitative sensory testing revealed impaired cold detection thresholds in 84% of men and 39% of women. Lower leg intraepidermal nerve fiber density (IENFD) was reduced to 46% in Fabry patients compared to controls and to 12.5% in men with impaired renal function. Patients with abnormal IENFD more often had pain. Group means for IENFD did not improve under enzyme replacement therapy (ERT), but IENFD in the back increased under ERT in 4/15 patients with good renal function and clinical improvement. Cutaneous cytokine gene expression did not differ from controls. We conclude that ERT may improve proximal skin innervation in patients with good renal function, but does not protect small fiber function in men with impaired renal function.     

Utility of Skin Biopsy to Evaluate Peripheral Neuropathy

Skin biopsy for epidermal nerve fiber analysis provides an important objective test for the diagnosis of peripheral neuropathy, particularly small fiber sensory neuropathy (SFSN). The determination of epidermal nerve fiber density (ENFD) is reliable, with high diagnostic specificity and good sensitivity. Because of false negatives, biopsy results must be interpreted in conjunction with neurologic findings and laboratory results, including objective tests of sensory and autonomic function. SFSN most commonly is length dependent and is idiopathic in about half the patients. Biopsy of a proximal site (thigh) and a distal site (calf) typically shows greater abnormality of ENFD distally than proximally. More severe abnormality of ENFD in the thigh than in the calf raises the possibility of a non–length-dependent SFSN. The causes of this type of neuropathy, such as Sjögren’s syndrome, sarcoidosis, and celiac disease, may be treatable.     

Effects of neutralizing antibodies to TNF-alpha on pain-related behavior and nerve regeneration in mice with chronic constriction injury

Inhibition of proinflammatory cytokines reduces hyperalgesia in animal models of painful neuropathy. We set out to investigate the consequences of this treatment for nerve regeneration. Here we examined the sequels of epineurial application of neutralizing antibodies to tumor necrosis factor-alpha (TNF) in chronic constriction injury (CCI) of the sciatic nerve in C57/BL 6 mice. The mice were tested behaviorally for manifestations of thermal hyperalgesia and mechanical allodynia. Nerve regeneration was assessed by morphometry of myelinated nerve fibers in the sciatic nerve and of the epidermal innervation density in the glabrous skin of the hindpaws. Antibodies to TNF reduced thermal hyperalgesia and mechanical allodynia after CCI. Myelinated fiber density in the sciatic nerve was reduced to 30% of normal on day 7 after surgery, and reached 60% on day 45, with no difference between antibody-treated and untreated animals. Epidermal innervation density as shown by PGP 9.5 and CGRP immunohistochemistry was reduced to 25-47% at both time points after CCI, again without differences between antibody treated and untreated mice. Myelinated fiber density but not epidermal innervation density was correlated to thermal and mechanical withdrawal thresholds. We conclude that neutralization of endoneurial TNF attenuates pain related behavior but has no effect on nerve regeneration. Furthermore, the number of epidermal nerve fibers is not relevant to the magnitude of behavioral hyperalgesia in CCI.     

Electrophysiological aspects of sensory conduction velocity in healthy adults. 2. Ratio between the amplitude of sensory evoked potentials at the wrist on stimulating different fingers in both hands.

The normal ratio between the amplitude of the sensory evoked potential (SEP) at the wrist on stimulating digits 1, 2, 3, and 5 was determined in 44 healthy adult subjects. The first digit had the larger amplitude, and the fifth digit the smallest SEP. The amplitude expresses the density of sensory innervation in each finger. The ratio between the amplitude of different fingers varied according to the age of the subject. The amplitude of the SEP from a digit innervated by the median nerve decreased in the elderly more than the SEP amplitude of the digit innervated by the ulnar nerve, probably because of a chronic compression in the carpal tunnel. The changes in the normal amplitude ratio can be applied to the topographic diagnosis of radicular and brachial plexus lesions if a fixed segmental sensory innervation of the hand is accepted. In 44 right handed subjects the amplitude of the sensory evoked potentials at the wrist was significantly larger in the left hand. This asymmetry of sensory innervation between hands could be physiological, and suggests a greater density of sensory innervation in the left hand of right handed subjects.     

Changes in intraepidermal nerve fiber and Langerhans cell densities in the plantar skin of rats after mercuric chloride exposure

Mercury and its compounds possess strong neurotoxicity and patients with mercury poisoning often report pain and numbness in the distal extremities that conform to the “stocking–glove” pattern. However, no study has investigated whether damage to small nerve fibers is associated with mercury poisoning. The aims of the present study were to evaluate the effects of different doses of mercury chloride (HgCl₂) on intraepidermal nerve fibers density (IENFD) and Langerhans cells (LCs) in the plantar skin of rats and to assess the possible relationship between changes in IENFD and sensory testing. Male Sprague–Dawley rats were divided into three experimental groups and administered HgCl₂ solutions via gavage at three different doses (4.25, 8.5, and 17 mg/kg/day) for 21 days. Subsequently, behavioral tests and pathological changes in IENFD and LCs were assessed at three different time points (1, 2, and 3 weeks). Rats in all three HgCl₂ groups exhibited varying degrees of weight and hair loss. Thermal hypersensitivity was evident in all the HgCl₂ groups (for middle‐2w subgroup, p < 0.05). Mechanical sensitivity tests revealed hyposensitivity in all the HgCl₂ groups except the high‐1w subgroup. Significant decreases in IENFD (for the high‐1w, middle‐1w, low‐2w, and low‐3w subgroups, p < 0.05) and significant increases in the density of LCs (except for the low‐1w and high‐2w subgroups, all p < 0.05) were found in all groups after HgCl₂ exposure. An association analysis revealed a significant correlation between the decrease in IENFD and the increase in LCs densities (r = ?0.573, p < 0.01). The present study demonstrated a decrease in IENFD and an increase in LCs density in the plantar skin of rats after HgCl₂ poisoning, indicating that damage of the small nerve fibers occurs after mercury poisoning.     

Skin and self‐injury: a possible link between peripheral innervation and immune function?

The aim of this preliminary case study series was to investigate epidermal innervation in pediatric patients with significant neurological impairment and self‐injurious behavior. We enrolled four pediatric patients with self‐injury (two males, two females; mean age 12y, range 9–14y) and used archival specimens from healthy, age‐matched children with typical development for comparison purposes. Epidermal nerve fiber density, peptide content, and mast cell degranulation patterns from non‐damaged skin were tested between the patients and the comparison group. The male patients with self‐injury had significantly increased epidermal nerve fiber densities, increased substance P positive fiber count and extensive mast cell degranulation compared with sex‐ and age‐matched individuals with typical development. Our case series shows for the first time altered peripheral innervation from non‐damaged tissue in children with significant self‐injury and developmental disability compared with a healthy comparison group. Establishing the role of peripheral nociceptive and immune modulatory neural pathways may offer new treatment avenues for this devastating neurobehavioral disorder.