An elderly gentleman, a known case of multiple myeloma from past 2 years presented to OPD with complaints of breathing difficulty last few weeks. The patient was under remission for the last 6 months, before this visit. On examination, the patient has biphasic stridor and progressive dyspnoea and the rest was unremarkable
CT revealed multiple lytic lesions in axial and appendicular skeleton (Fig 1). Larynx revealed soft tissue lesions involving cricoid and arytenoid cartilages causing thinning of them and showing mass effect in form of narrowing of the airway with resultant difficulty in breathing and stridor (Fig 2 A, B and C). However, there was no intraluminal extension of soft tissue component seen. These findings were also correlated with PET imaging which revealed mildly FDG avid lesions in laryngeal cartilages. (Fig 3) The patient was also referred for bronchoscopy to look for the cause, which revealed subglottic stenosis due to submucosal bulge with normal overlying mucosa. Hence mucosal growths (including squamous malignancy) were ruled out.
Multiple myeloma (MM) is the most frequent cancer involving the skeleton with the median age of 69 years.  Plasma cell neoplasms (PCNs): systemic [multiple myeloma (80%)] and localised [solitary plasmacytoma (5%)]. Solitary plasmacytoma can further be divided into extramedullary plasmacytoma (EMP) and solitary bony plasma (SBP) according to their site of occurrence: EMP occurs in soft tissues and SBP occurs in the bone marrow. Subglottic mass in elderly males can have multiple differentials but when patient has history of multiple myeloma and now presenting with subglottic mass, EMPs must considers merit.
There are two proposed mechanisms of myeloma of laryngeal cartilage (MLCs): (1) Direct invasion by adjacent plasmacytoma and (2) Osseous metaplasia of cartilage into bone marrow. 
MLCs arising from direct invasion of laryngeal cartilage by adjacent soft tissue EMP has been proposed by multiple authors. It is supported by radiological features of MLCs that indicate invasion of laryngeal cartilage from adjacent structures. Second mechanism is osseous metaplasia of cartilage resulting in formation of hematopoietic tissue within the laryngeal cartilage often found among elderly as part of normal aging process; however, they rarely involve myelomatous changes to become the site of abnormal plasma cell proliferation, such as in MLCs. 
Clinical presentations includes progressive airway obstruction, including dyspnoea, stridor, hoarseness, and dysphagia. A palpable neck mass was reported in 38% cases.  In our case, progressive dyspnoea and stridor were the main symptoms. No palpable neck mass was seen in our case. A common finding on laryngoscopy is supra- or subglottic stenosis due to bulging mass with normal overlying mucosa, similar to present case. There were no significant enlarged lymph nodes similar to available literature. The imaging characteristics suggesting EMPs arising from the cricoid consist of thinning and expansion of the cartilage laminae without mucosal lesions nor soft tissue mass adjacent to the cricoid cartilage . In present case, similar findings were seen involving cricoid and both arytenoid cartilages. Surgical resection alone has better results in resectable disease . Our patient was tracheostomised for few days followed by endoscopic laser surgery to treat subglottic stenosis and kept on follow up for radiotherapy treatment. Patient tolerated procedure well and discharged subsequently. Histopathological examination was not done as patient was a known case of MM.
Written informed consent has been obtained from the patient to publish this case report.
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