摘要Background:Late-onset multiple acyl-coA dehydrogenase deficiency (MADD) is an autosomal recessive inherited metabolic disorder.It is still unclear about the muscle magnetic resonance image (MRI) pattern of the distal lower limb pre-and post-treatment in patients with late-onset MADD.This study described the clinical and genetic findings in a cohort of patients with late-onset MADD,and aimed to characterize the MRI pattern of the lower limbs.Methods:Clinical data were retrospectively collected from clinic centers of Peking University People's Hospital between February 2014 and February 2018.Muscle biopsy,blood acylcarnitines,and urine organic acids profiles,and genetic analysis were conducted to establish the diagnosis of MADD in 25 patients.Muscle MRI of the thigh and leg were performed in all patients before treatment.Eight patients received MRI re-examinations after treatment.Results:All patients presented with muscle weakness or exercise intolerance associated with variants in the electron transfer flavoprotein dehydrogenase gene.Muscle MRI showed a sign of both edema-like change and fat infiltration selectively involving in the soleus (SO) but sparing of the gastrocnemius (GA) in the leg.Similar sign of selective involvement of the biceps femoris longus (BFL) but sparing of the semitendinosus (ST) was observed in the thigh.The sensitivity and specificity of the combination of either "SO+/GA-" sign or "BFL+/ST-" sign for the diagnosis of late-onset MADD were 80.0％ and 83.5％,respectively.Logistic regression model supported the findings.The edema-like change in the SO and BFL muscles were quickly recovered at 1 month after treatment,and the clinical symptom was also relieved.Conclusions:This study expands the clinical and genetic spectrums of late-onset MADD.Muscle MRI shows a distinct pattern in the lower limb of patients with late-onset MADD.The dynamic change of edema-like change in the affected muscles might be a potential biomarker of treatment response.