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

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.

Inclusion criteria

• Adults diagnosed with fibromyalgia (FM) according to the 2016 revised American College of Rheumatology (ACR) diagnostic criteria; or
• Adults diagnosed with myofascial pain syndrome (MPS) based on standardized clinical examination, including identification of a symptomatic muscle, palpable taut band, and clinically relevant myofascial trigger point. Musculoskeletal ultrasonography was additionally performed in all participants with MPS as a supportive phenotyping method.
• Ability to understand and complete the clinical assessment questionnaires.
• Provision of written informed consent for participation and genetic analysis.

Exclusion criteria

• Presence of both fibromyalgia and myofascial pain syndrome or fulfillment of the 2016 revised ACR criteria for fibromyalgia in participants considered for the MPS group.
• Presence of another medical, neurological, rheumatological, or musculoskeletal condition that could substantially interfere with pain assessment or clinical phenotyping.
• Inability to complete the study assessments.
• Insufficient or unsuitable blood sample for genetic analysis.