THE FAULT IN OUR MOSAIC PATTERNS: PULMONARY HYPERTENSION MISSED AND TREATED AS HYPERSENSITIVITY PNEUMONITIS

Abstract

TOPIC: Pulmonary Vascular Disease TYPE: Medical Student/Resident Case Reports INTRODUCTION: Mosaic Pattern refers to areas of variable lung attenuation seen on Computed Tomography (CT) of the chest. The pattern is a nonspecific finding and can be associated with airway, infiltrative lung, or pulmonary vascular diseases[1]. We present a case of exertional dyspnea with mosaic pattern on high resolution CT (HRCT) that was initially misdiagnosed and treated as hypersensitivity pneumonitis (HP) and found later to be caused by pulmonary arterial hypertension. CASE PRESENTATION: A 70-year-old Caucasian female presented with worsening exertional dyspnea after percutaneous coronary intervention. HRCT of the chest done at an outside office showed mosaic pattern and few tiny bilateral nodules with no fibrotic changes that was interpreted as possible chronic hypersensitivity pneumonitis. She was started on prednisone 40mg daily with minimal improvement in symptoms and referred to our Interstitial Lung Disease (ILD) Clinic for further work up and treatment. Upon interviewing the patient, she reported previous intake of anorexigenics (dextroamphetamine) in her 20's for 2 months. Review of the HRCT study showed parenchymal changes were not consistent with any specific ILD pattern and no exaggeration of mosaic pattern with expiratory cuts suggesting the presence of pulmonary hypertension and absence of significant air trapping. Prednisone was tapered off, and serologic work up showed no evidence of connective tissue disease. 6-minute walk test revealed severe reduction in exercise capacity with patient covering 38m which was 12% of predicted distance, and spirometry showed moderate-severe restrictive defect. Her echocardiography showed normal LV systolic function with ejection fraction (55-65%), and her ventilation-perfusion (VQ) scan was negative for any embolic disease. The patient was admitted to the hospital for hypervolemia and after adequate diuresis, a detailed hemodynamic study by right heart catheterization for the assessment of pulmonary hypertension was done. Results showed increased mean pulmonary artery pressure (mPAP) (31 mmHg) at rest; however, during limited exercise challenge which she could not complete, pulmonary artery occlusion pressure (PAOP) increased to 23 mmHg suggesting decreased left atrial/ventricular compliance. She was started on sildenafil and discharged with close follow up. DISCUSSION: Air-trapping in airway diseases causing relative hyperemia of healthy lungs, pulmonary vascular diseases causing relative oligemia in hypo-perfused lungs, and parenchymal disease presenting as patchy ground-glass opacities, all can give a mosaic pattern on CT[1]. Infiltrative diseases and airway diseases are reliably differentiated as the cause of mosaic attenuation on CT scan, but vascular diseases are often misinterpreted.[2] CONCLUSIONS: Careful review of HRCT with a chest radiologist in an advanced lung disease center is necessary to avoid misdiagnoses and unnecessary treatments. REFERENCE #1: Stern, Eric J., et al. "CT mosaic pattern of lung attenuation: distinguishing different causes.” AJR. American journal of roentgenology 165.4 (1995) REFERENCE #2: Worthy, Sylvia A., et al. "Mosaic attenuation pattern on thin-section CT scans of the lung: differentiation among infiltrative lung, airway, and vascular diseases as a cause.” Radiology205.2 (1997) DISCLOSURES: No relevant relationships by Roberto Bernardo, source=Web Response No relevant relationships by Salim Daouk, source=Web Response No relevant relationships by Ahmad Hassan, source=Web Response No relevant relationships by Abed Madanieh, source=Web Response No relevant relationships by Chirin Orabi, source=Web Response