Diffuse pulmonary ossification is a rare entity of characterized by diffuse small bone fragments in lung tissue. Two types are described: ‘nodular’ and ‘dendriform’. Living cases are rarely encountered; most are diagnosed at autopsy.
A 29-year-old man had a moderate chest pain ongoing for two weeks was referred to our hospital with bilateral, multifocal, diffuse calcified nodular densities on chest radiography and computed tomography (CT). Use of risperidone and valproic acid due to bipolar personality disorder for three years, working as a car repairer for one year were present in his history. On positron emission tomography (PET-CT) was taken for suspected metastatic disease, increased metabolic activity was detected in multiple nodules with low density. Video-assisted thoracic surgery (VATS) lung biopsy was performed for diagnose. Even though macroscopic appearance of specimens suggestive of malignancy, histopathology was consistent with DPO. Drugs used by the patient were found not to be the direct cause of pathology in lung however previous studies have reported valproic acid effects osteogenesis in vitro and in vivo through by mesenchymal pluripotent cell proliferation and differentiation in extracellular matrices. Although the exact pathogenesis of diffuse pulmonary ossification is unknown, underlying fibrosis is the precursor of DPO has been shown. Also pulmonary fibrosis can be triggered with deposition of heavy metals (eg., serium oxid/ phosphate). Based on this, sodium valproate and heavy metals may play a role in inflammation-mediated heterotopic ossification was considered in our case.
In conclusion, we herein presented a case of living DPO accompanied by an inflammation-mediated heterotopic ossification related to sodium valproate and/or heavy metals with high probability.