Evaluation of subclinical organ involvement with ultrasound elastography in childhood familial Mediterranean fever: relationships with disease activity, inflammatory markers, colchicine response, and genotype.

UNLABELLED: This study evaluates multiorgan shear-wave elastography (SWE) in children with familial Mediterranean fever (FMF) during attack-free periods and examines associations with clinical and inflammatory parameters. In this single-center, retrospective cross-sectional case-control study, SWE measurements of the liver, spleen, bilateral kidneys, pancreas, four mesenteric fat regions, and bilateral thyroid lobes were evaluated in 75 children with FMF and 52 matched healthy controls. Adjusted linear regression, generalized estimating equation (GEE), and Benjamini-Hochberg correction were applied. The cohort included 127 children; age, sex, weight, height, and BMI were comparable between groups. After adjustment for age, sex, and BMI, FMF patients showed higher SWE values at all 11 sites: liver (β = 3.25 kPa; 95% CI, 2.55-3.95), right kidney (β = 0.94 kPa; 95% CI, 0.31-1.57), left kidney (β = 1.15 kPa; 95% CI, 0.57-1.74), spleen (β = 1.24 kPa; 95% CI, 0.55-1.93), pancreas (β = 0.88 kPa; 95% CI, 0.21-1.55), mesenteric fat regions (β range, 1.43-2.06 kPa), right thyroid lobe (β = 1.62 kPa; 95% CI, 0.73-2.51), and left thyroid lobe (β = 2.94 kPa; 95% CI, 2.05-3.83). Repeated-measures GEE showed an overall adjusted FMF-control difference of 1.71 kPa and a significant group × organ-site interaction. Exploratory analyses showed no FDR-significant associations with disease duration, diagnostic delay, ISSF score, attack-free CRP/ESR, colchicine responsiveness, or M694V/M694V genotype.

CONCLUSION: Children with FMF had higher multiorgan and mesenteric fat SWE-derived stiffness during attack-free periods. Multiorgan SWE may help evaluate subclinical tissue-level changes in pediatric FMF, but the cross-sectional design, lack of histopathologic validation, and exploratory subgroup analyses preclude causal or therapeutic conclusions.

WHAT IS KNOWN: • Familial Mediterranean fever may be associated with persistent subclinical inflammation during attack-free periods. • Shear-wave elastography can noninvasively quantify tissue stiffness.

WHAT IS NEW: • Children with FMF showed higher liver, spleen, kidney, pancreas, thyroid, and mesenteric fat stiffness than controls. • These differences persisted after adjustment for age, sex, and BMI.