Plasma cell mucositis is a rare idiopathic condition consisting of a marked infiltration of mucosa by plasma cells that may involve the mucous membranes of the upper aerodigestive tract—namely, the oral mucosa, gingiva, supraglottic and glottic larynx, and the trachea. While plasma cell mucositis is usually considered benign, cases of critical stenosis of the upper airway have been reported.^1,2 We present a case of plasma cell mucositis involving the trachea and bronchi. This pattern of lower respiratory tract involvement has not previously been described.

A 55 year old woman, a lifelong non-smoker, presented with chronic cough, dyspnoea, and stridor. Pulmonary function tests showed a moderately severe obstructive ventilatory defect with forced expiratory volume in 1 second (FEV₁) of 1.44 l (56% of predicted), forced vital capacity (FVC) of 3.00 l (96% of predicted), and a FEV₁/FVC of 48%. Bronchoscopy revealed narrowing of the left mainstem bronchus (fig 1) and diffuse mucosal abnormalities of the bronchial tree. A biopsy specimen showed a dense plasma cell infiltrate of the mucosa consistent with plasma cell mucositis. Molecular analysis for heavy chain immunoglobulin rearrangement failed to demonstrate a clonal B cell population of lymphocytes. Before starting treatment the patient had an episode of hypoxaemic respiratory failure requiring intubation and mechanical ventilation secondary to a mucus plug occluding her left mainstem bronchus which was removed. She was placed on prednisone 1 mg/kg with improvement in her symptoms. Because of the severity of her symptoms, cytotoxic therapy was initiated with chlorambucil 30 mg with monthly pulses of prednisone 100 mg daily for 4 days. There was marked improvement in her symptoms during the pulse of corticosteroids but this was not sustained. After 4 months of treatment pulmonary function studies remained unchanged. Bronchoscopic examination revealed persistent bronchial mucosal abnormalities with plasma cell infiltrate on endobronchial biopsy. The patient remained symptomatic and underwent bronchoscopy with argon plasma coagulation with debridement of the affected mucosa and subsequent recanalisation of the left mainstem bronchus with dramatic symptomatic improvement.

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Figure 1

 Left mainstem bronchus before treatment.

Plasma cell mucositis was first described in 1952 by Zoon³ in the context of glans penis involvement and has now has been reported to involve the vulva, buccal mucosa, lips, tongue, supraglottic larynx, glottic larynx, and the trachea. Although this condition is considered benign, previous reports have illustrated an aggressive clinical course. Two reported cases have described patients who ultimately required tracheostomy for airway compromise.² Surgical intervention and CO₂ laser excision have also been used in the setting of airway compromise.¹

Treatment for plasma cell mucositis is not established. Reports have described the use of both topical and systemic corticosteroids,^4,5 cytotoxic and radiation therapy,² and surgical intervention.¹ In our patient debridement of the affected mucosal tissue of the left mainstem bronchus with argon plasma coagulation resulted in symptomatic improvement. In many instances treatment regimes have resulted in stabilisation of disease but have not consistently been associated with disease regression.

Long term prognosis appears good. One case series of nine patients showed that patients were alive with disease up to 16 years after the initial diagnosis.¹ No cases with progression of disease to lymphoma have been reported.