A hyper-ferritinemia syndrome evolving in recurrent macrophage activation syndrome, as an onset of amyopathic juvenile dermatomyositis: A challenging clinical case in light of the current diagnostic criteria

• Persistent hyper-ferritinemia can be associated to several systemic rheumatic diseases.
• Sudden elevation of hyper-ferritinemia up to very high values in the clinical setting of FUO should increase the suspicion of ongoing MAS.
• Current diagnostic criteria for HLH might not be enough sensitive in order to diagnose MAS appropriately.
• A delay in the diagnosis of macrophage activation syndrome might lead to severe and life-threatening complications.

Juvenile dermatomyositis is an immune-mediated inflammatory multi-system disease involving mainly striated muscles and skin. Typical dermatological features are fundamental to establish the diagnosis, especially whenever the myopathy is very mild or absent, as it occurs in the form called as amyopathic juvenile dermatomyositis. Sometimes, systemic rheumatic diseases can develop a hyperferritinemia syndrome characterized by hemophagocytosis, namely macrophage activation syndrome, which represents a severe and life-threatening complication. Here, we describe a complex clinical history characterized by a hyper-ferritinemia syndrome after infectious mononucleosis, leading to recurrent episodes of macrophage activation syndrome. Finally, the late onset of several skin changes brought to a diagnosis of amyopathic juvenile dermatomyositis.