# Skin layer thickness, muscle elasticity and their effects on pain level in fibromyalgia patients

## TL;DR

Fibromyalgia patients have thinner skin and stiffer muscles, which may contribute to their chronic pain.

## Contribution

This study identifies thinner skin and increased muscle stiffness as potential contributors to peripheral sensitization in fibromyalgia.

## Key findings

- FM patients have significantly thinner skin compared to healthy controls.
- Trapezius muscle stiffness correlates strongly with pain severity in FM patients.
- Reduced skin thickness may play a role in peripheral sensitization in fibromyalgia.

## Abstract

•Fibromyalgia patients have thinner skin on ultrasound.•Trapezius muscle is thicker and stiffer in fibromyalgia.•Muscle stiffness is correlated with pain severity.•Reduced skin thickness may drive peripheral sensitization.

Fibromyalgia patients have thinner skin on ultrasound.

Trapezius muscle is thicker and stiffer in fibromyalgia.

Muscle stiffness is correlated with pain severity.

Reduced skin thickness may drive peripheral sensitization.

Fibromyalgia (FM) is a chronic, non-inflammatory syndrome characterized by widespread body pain, fatigue, sleep disturbances, impaired cognitive function and anxiety. Peripheral and central sensitization are thought to cause chronic pain in this disorder, which impairs quality of life. No specific laboratory test, radiographic method, or biomarker has been identified for diagnosis. As its physiopathology is not fully understood, no specific treatment has been identified. At this stage, studies are needed to facilitate diagnosis and guide treatment.

Eighty-nine women with FM and 36 healthy controls were enrolled in this cross-sectional, case-controlled, single-centre study. FM-related measurements (number of tender points, myalgic score, pain Visual Analogue Scale [VAS]) were recorded. All participants underwent an analysis of trapezius muscle thickness and elasticity. Skin and subcutaneous tissue thickness, and hypodermis thickness were measured by using B-mode Ultrasonography (USG) and tension (compression) Sonoelastography (SEL).

Skin thickness was lower in FM patients than in healthy controls (p < 0.01). Both trapezius muscle thickness and elastography scores were higher in the FM group compared to controls (p < 0.05 and p < 0.001, respectively). A significant correlation was found between VAS score and elastography scores (r = 0.661, p < 0.001); however, there was no significant correlation between VAS score and trapezius or skin thickness.

Patients with FM have lower skin thickness and higher trapezius muscle thickness and elastography scores than healthy controls. The thinner skin thickness in FM compared to controls may represent a potentially important factor in the pathophysiological mechanism of peripheral sensitization.