Background: Currently, musculoskeletal ultrasound (MSUS) holds significance in predicting the progression of psoriatic (PsA) and rheumatoid arthritis (RA) in individuals at risk. The lack of diagnostic biomarkers for PsA may lead to delayed diagnosis and the development of clinical and radiological damage.
Objectives: To assess the role of MSUS in early diagnosis of RA and PsA: correlation with clinical disease activity scores.
Patients and methods: Twenty patients with RA fulfilling the criteria of EULAR/ACR 2010, twenty patients with PsA fulfilling the criteria of CASPAR classification and twenty age and sex matched healthy persons as control.  Musculoskeletal examination, complete blood count, liver function, renal function, erythrocyte sedimentation rate, C-reactive protein, rheumatoid factor, anti-nuclear antibody, anti-citrullinated protein antibody, clinical, simplified activity scores, DAS-28ESR, DAS-28CRP, USDAS28 scores, and plain x-ray both hands.
Results: In RA patients, 12 (20.0%); 11 (55.0%) PsA patients were positive for bone erosions; 4 (20.0%) patients with RA; 8 (40.0%) patients with PsA had synovitis; 13 (65.0%) RA patients, 15 (75.0%) PsA patients were clinically active; 6 (30.0%) patients with RA;  9 (45.0%) patients with PsA demonstrated significant disease activity using PDUS (p=0.002). There was a significant correlation between DAS-28ESR (p=0.001), DAS28-CRP(P=0.001), USDAS-28ESR (p<0.001), USDAS-28CRP (p<0.001) and disease activity scores. MSUS shows flexor tendon tenosynovitis in RA and characteristic findings of enthesitis in PsA patients.
Conclusion: MSUS in rheumatoid arthritis can detect early inflammation. In PsA, it complements clinical examination, adding sensitivity and specificity in identifying inflammatory and structural lesions, thus improving qualitative assessment.