Eosinophilic granuloma presenting as post-traumatic scalp hematoma with epidural hemorrhage. A case report.

Langerhans cell histiocytosis (LCH) encompasses a range of clinical presentations. Pure osseous involvement is referred to as eosinophilic granuloma (EG), whereas systemic involvement can either be classified as Hand-Schuller-Christian disease or Letterer-Siwe syndrome. It is estimated that of the total incidence of LCH (0.5 per 100,000 children per year in the United States), nearly 70% are categorized as EG (1). We describe a case of clinically occult calvarial eosinophilic granuloma brought to medical attention only after a traumatic event led to scalp and epidural hemorrhage at the site of the lesion. Osseous EG initially presents as a painful or tender mass, at times even mimicking osteomyelitis. Computed tomography (CT) reveals a lytic lesion with beveled edges. Magnetic resonance (MR) imaging is often non-specific, but usually demonstrates a marrow-replacing process that is T1 hypointense, T2 hyperintense, with homogenous enhancement. The complex MR imaging findings in our case provided a unique perspective regarding the presentation of EG. Once pathology established eosinophilic granuloma, skeletal survey confirmed the lesion was solitary, despite a compelling history of present illness.