Cheesy casts: Lymphatic plastic bronchitis in an adult

ABSTRACT

Introduction: Plastic bronchitis (PB) is a rare entity which involves expectoration of bronchial casts made of thick tenacious mucus. It is more commonly seen in children after cardiac surgery for congenital heart diseases, but has been reported in adults and is associated with <20 systemic/pulmonary illnesses like tuberculosis (TB), cystic fibrosis (CF) and lymphatic anomalies (LA). Here, we report a case of PB due to a thoracic duct (TD) malformation. Case Description A 24-year-old woman with Graves' disease presented to the emergency department (ED) with a 1-month history of unremitting cough with expectoration of thick white casts. She reported associated malaise but denied fevers, chest pain, or hemoptysis. She was a former smoker and denied any history of congenital heart disease or cardiac surgeries. In the ED, she was afebrile (36.8°C ), normotensive (134/74 mmHg), and saturating 100% on room air. Initial labs were significant for low TSH (<0.01 uIU/ml) and high free thyroxine (1.9 ng/dl). COVID-19 PCR and respiratory viral panel was negative. Computed tomography chest showed pan-lobar centrilobular ground glass (left greater than right), enlarged thyroid and thymus. Autoimmune workup(ANA, c-ANCA, p-ANCA, Anti-GBM Ab, SSA), Aspergillus fumigates antibodies, sweat chloride test, and quantitative immunoglobulins were unrevealing. Bronchoscopy with bronchoalveolar lavage (BAL) on day 3 showed a left upper lobe cast (Figure 1). Cytology revealed a significant number of lymphocytes and macrophages in a background of mucin. BAL acid fast bacilli, bacterial, and fungal cultures were negative. Patient was discharged on day 3 for outpatient workup. Magnetic resonance lymphangiogram showed abnormal lymphatic flow from the TD into the mediastinum consistent with lymphatic PB. Subsequent lymphangiography demonstrated prominent left greater than right lymphatic malformation arising from the mid TD extending into the lung parenchyma which was successfully embolized. The patient reported complete resolution of her symptoms post-procedure. Discussion: PB is a rare disease which presents as expectoration of bronchial casts. It has been associated with various pulmonary/systemic illnesses with LA being one of them. The mechanism of cast formation in LA involves engorgement of the bronchial submucosa with slow seepage of lymph into the bronchial lumen which eventually desiccates and form casts. It can remain silent for years and manifest in adulthood after any physiologic stressor. In our patient, the likely physiologic stressor is her Graves' disease. Percutaneous lymphangiogram followed by TD embolization is a less invasive intervention shown to provide a successful resolution of symptoms in patients with lymphatic PB.