Gelatinous Transformation of Bone Marrow in the Calcaneus, Diagnosed by Open Bone Biopsy in a Patient With Anorexia Nervosa: A Case Report

Gelatinous transformation of bone marrow (GTBM) is a complication of various diseases, one of which is anorexia nervosa (AN). We describe a rare case of a 20-year-old man who presented to our clinic with a 3-month history of heel pain without trauma. At presentation, he was noted to have a low body mass index (BMI) of 16.2 kg/m2 and pancytopenia. On magnetic resonance imaging, the left calcaneus showed low intensity on T1-weighted and high intensity on T2-weighted images. Open biopsy was done because we suspected that the lesion was either a lymphoproliferative tumor or a trabecular-type bone metastatic tumor. However, tissue histology of bone samples showed atrophy of fat cells with deposition of gelatinous material and a decreased hematopoietic cell population. Therefore, we made a diagnosis of GTBM, most likely caused by AN. We started treatment with nutritional support, and 6 months later, the hematological parameters returned to normal and BMI improved to 19.4 kg/m2. He was able to return to work and had no left heel pain. This case indicates that foot and ankle surgeons need to be aware of this rare pathology, although it might be difficult to diagnose without biopsy. To our knowledge, very few descriptions of GTBM in the calcaneus have been reported to date