Serum vitamin D status, ultrasonographic assessment, and their association with severe sarcopenia in some rheumatic diseases and their correlation with disease activity

Background and aim Sarcopenia is a prevalent issue in chronic inflammatory conditions such as rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), and spondyloarthritis (SpA), leading to increased morbidity and reduced quality of life. This study explores the relationship between serum vitamin D levels, ultrasonographic muscle measurements, sarcopenia, and disease activity with RA, SLE, and SpA. Patients and methods A cross-sectional study included 140 patients (60 RA, 40 SLE, 40 SpA) and 80 healthy controls aged 18–65 years. Patients were assessed for sarcopenic parameters, including hand grip strength, chair stand test, SARC-F questionnaire, and muscle percentage. Ultrasonographic measurements of the biceps, rectus femoris, and vastus lateralis were performed. Vitamin D levels and disease activity indices (Disease Activity Score in 28 joints, Systemic Lupus Erythematosus Disease Activity Index, and Ankylosing Spondylitis Disease Activity Score) were analyzed for correlations with sarcopenic parameters. Results Patients exhibited significant sarcopenic impairments compared to controls ( P <0.001), even in the presence of low vitamin D levels. Among rheumatic groups, SLE patients showed the greatest deficits in strength, function, and muscle size, followed by RA and SpA. Disease activity was strongly correlated with reduced muscle function and strength in RA and SpA. Vitamin D levels showed protective associations with sarcopenia severity. Conclusion These findings emphasize the importance of ultrasonographic and vitamin D assessments in the early detection and management of sarcopenia, guiding targeted interventions to improve patient outcomes.