Technetium-MDP Bone Scan/SPECT CT Findings in Erdheim-Chester Disease: A Case Report of Skull and Ribs Involvement

Erdheim-Chester disease (ECD) is a rare disorder of the non-Langerhans cell histiocytes with associated infiltration of multiple organ systems. Skeletal involvement is characteristically bilateral and symmetric, exhibiting an osteosclerotic pattern in the metaphysis and diaphysis of the long bones, usually sparing the epiphysis. It is quite a rare disease with less than one hundred cases reported in the literature. We report a case of a 31 year old retroviral disease positive female patient who presented with a history of right sided hemiplegia and aphasia and subsequently diagnosed to have ECD histologically following a brain biopsy. A technetium-99m methylene diphosphonate ((99m)Tc-MDP) bone-scan done showed osteoblastic lesions in the left lateral parietal skull and in the right 4th-6th ribs anteriorly and the right 10th rib antero-laterally. The patient had irradiation of the intracranial mass and is presently on interferon. ECD though a rare disorder also presented with a rare skull and ribs involvement in this patient.