T Bartalena, M Rinaldi, E Rimondi, G Rossi, D Bartalena
mri., solar erythema
T Bartalena, M Rinaldi, E Rimondi, G Rossi, D Bartalena. Sunburn appearance on MRI. The Internet Journal of Radiology. 2008 Volume 10 Number 2.
The appearance of solar erythema as an incidental finding in a knee MRI scan is shown.
A 48 years old male was referred for MRI of his right knee because of a suspected torn medial meniscus. MRI showed a longitudinal tear of the posterior horn of the medial meniscus and a moderate articular effusion. However an unexpected finding was brought to the attention of the interpreting radiologist: abnormal signal hyperintensity was present on the proton density weighted fat suppression (PDFS) sequences in the subcutaneous soft tissue in the anterolateral aspect of the knee (Fig.1A-B). At the end of the MRI scan, physical examination of the patient was performed and revealed erythema of both thighs consistent with a sunburn (Fig.1C). The patient confirmed he passed the day before at the beach and forgot to use his sunscreen lotion.
Soft tissues hyperintensity on fluid sensitive sequences is an aspecific MRI finding that may be encountered in a variety of situations including infectious etiologies ranging from simple cellulitis to life threatening conditions like necrotizing fasciitis , and noninfectious causes like cellulitis accompanying venous thrombosis , rheumatologic diseases like dermatomyositis  or to benign causes like fluid overload  or simple solar erythema like the case we presented. Clinical history and physical examination are fundamental in the differential diagnosis.