COMT and IL6 Genotype-Phenotype Associations in Fibromyalgia and Myofascial Pain Syndrome

Overview

Fibromyalgia (FM) and myofascial pain syndrome (MPS) are chronic pain conditions that may share some clinical features but differ in the distribution and extent of pain and associated symptoms. The biological factors contributing to these differences remain incompletely understood. This observational study aims to compare the distribution of two pain-related genetic variants, COMT rs4680 and IL6 rs1800795, between individuals with FM and MPS and to investigate their associations with clinical characteristics. Participants will undergo standardized clinical assessment, including measures of symptom burden, physical functioning, and energy/fatigue. In participants with MPS, musculoskeletal ultrasonography will be used as an adjunct to clinical examination to support phenotypic characterization. Genetic analysis will be performed using DNA obtained from peripheral venous blood. COMT rs4680 and IL6 rs1800795 will be genotyped using a TaqMan probe-based real-time polymerase chain reaction method. The study is intended to explore genotype-phenotype associations in two clinically characterized chronic pain conditions. The investigated genetic variants are not being evaluated as diagnostic tests, and no intervention is assigned as part of the study.

This comparative observational study will include 50 participants, comprising 25 individuals with fibromyalgia (FM) and 25 individuals with myofascial pain syndrome (MPS). FM will be diagnosed according to the 2016 revised American College of Rheumatology diagnostic criteria. MPS classification will be based on a standardized sequential assessment consisting of clinical examination followed by musculoskeletal ultrasonography. Clinical examination will be performed to identify the symptomatic muscle, palpable taut band, and clinically relevant myofascial trigger point. Ultrasonography will subsequently be performed in all participants classified as having MPS and will be used as an adjunct to clinical examination rather than as a standalone diagnostic test. Clinical assessment will include the Revised Fibromyalgia Impact Questionnaire (FIQR), Symptom Severity Scale (SSS), and the Physical Functioning and Energy/Fatigue domains of the 36-Item Short Form Health Survey (SF-36). Peripheral venous blood samples will be obtained for DNA extraction. COMT rs4680 and IL6 rs1800795 polymorphisms will be genotyped using TaqMan probe-based real-time PCR. Genotype distributions will be compared between FM and MPS, and associations between genotype categories and clinical measures will be explored. The study is designed as a hypothesis-driven candidate-gene association study and does not aim to establish either polymorphism as a diagnostic genetic marker.