Plasma Cell Rich Osteomyelitis: A Rare Entity

Plasma cell rich osteomyelitis is a rare finding characterised by a plethora of plasma cells localised in the affected bone without the typical clinical features of infection. It usually affects the metaphysis of long bones with a radiological appearance as a dense thickening of bone without sequestrum formation. We present an atypical case of plasma cell osteomyelitis with a lesion in the metaphysis as well as the diaphysis of the humerus without sclerosis but with sequestrum formation. An 11-year-old girl was brought to OutPatient Department (OPD) with complaints of post-traumatic pain and swelling at left shoulder and proximal arm since one and a half months with aggravation of symptoms since last 10 days. Patient had also been treated for Urinary Tract Infection (UTI) by a paediatrician who prescribed antibiotics and antipyretics because of which fever subsided but the pain persisted. The x-ray of left shoulder with arm revealed a fracture of surgical neck of humerus with cortical irregularity noted in the mid-shaft of humerus along with lamellated periosteal reaction suggestive of post-traumatic osteomyelitis with a pathological fracture. Clinicoradiologic diagnosis of pathological fracture of left neck of humerus was made with an underlying neoplastic or infective aetiology. An open biopsy was taken from left proximal humerus. Histopathological examination showed plasma cells in sheets having abundant basophilic cytoplasm, round to eccentric nuclei and perinuclear hoff along with lymphocytes and few polymorphs with surrounding area showing fibrosis, oedema and hyperemia. A diagnosis of chronic plasma cell osteomyelitis was rendered, which is an uncommon condition without specific clinical findings and an ambigious cause. Histopathology is the definitive tool for obtaining an accurate diagnosis and we strongly recommend a meticulous histopathological examination correlated with clinico-radiological description for a correct diagnosis in order to avoid an increased frequency of diagnosis of neoplastic plasma cell lesion as well as for advocating the correct treatment. This case is discussed for presentation of plasma cell osteomyelitis and also to report a case of chronic primary plasma cell rich osteomyelitis with atypical clinical features.