MRI appearance of Erythema Nodosum
Erythema Nodosum secondary to streptococcal infections
History of recurrent streptococcal infections over the years; the patient developed pain and swelling in the left ankle.
Erythema nodosum lesions demonstrate low-to-intermediate signal on the T1-weighted images. On T2-weighted images, it shows heterogeneous hypointense signal, though hyperintense to the muscle/tendon signal. No blooming was demonstrated on the T2* sequence. EN shows hyperintense signal on T2-weighted fat-saturated images. On fat-saturated T1-weighted images, EN show subtle hyperintensity, brighter than the muscle signal.
EN, seen more frequently in younger females, requires an interdisciplinary approach to exclude all underlying causes. Streptococcal infections are the most common cause identified.
To the best of our knowledge, the MRI appearance of erythema nodosum on the different MR sequences in a single patient has not been described in the literature.