Aims

• Advance clinical taxonomy for multimorbidity. Develop, compare and validate disease and symptom classifications that bridge mental and physical conditions, capturing clusters, trajectories and endotypes that cut across specialties.
• Make symptoms and cross-system phenotypes central. Elevate entities such as migrainous vertigo (vestibular migraine) and post-exertional malaise (PEM) as test cases for classification, measurement and clinical pathways.
• Standardise definitions and data. Harmonise operational criteria, coding (ICD/SNOMED/LOINC/RxNorm), and phenotype algorithms; publish consensus statements and crosswalks.
• Link taxonomy to care. Show how better classification changes diagnosis, risk stratification, communication, treatment selection, and service design—especially for complex, multimorbid patients.
• Promote reproducibility and equity. Require transparent methods, sharable phenotype code lists, and analyses across age, sex/gender, ethnicity and resource settings.

Scope

• Taxonomy & nosology: New or revised case definitions; hierarchical and network-based disease models; phenotype/endotype frameworks. Symptom ontologies and measurement theory (e.g., intensity, duration, post-exertional dynamics, vestibular/aural features).
• Phenotyping methods: Rule-based and machine-learning phenotypes; cluster/latent class models; graph and trajectory modelling; multimodal data (EHR, wearable, imaging, psychometrics). External validation, transportability, and fairness/bias audits of phenotypes.
• Multilingual terminology & coding: Crosswalks between ICD/SNOMED and research definitions; term governance; effects of coding choices on epidemiology and service planning. “Data descriptor” articles releasing curated phenotype code lists and implementation recipes.
• Clinical implementation: Diagnostic pathways, decision tools, and care models for complex patients (e.g., co-occurring anxiety disorders and autonomic dysfunction with vestibular migraine; PEM management across ME/CFS and Long COVID clinics). Impact studies on outcomes, safety, costs and patient-reported measures.
• Trials & interventions: Interventional studies tailored to multimorbid phenotypes (including N-of-1 and adaptive designs), deprescribing strategies, and integrated psychological-somatic interventions.
• Policy, ethics and communication: Consequences of reclassification; medico-legal aspects; patient-centred nomenclature; language and stigma in diagnostic labels.