A40-02 The Great Imitator

Abstract Amyloidosis is a heterogeneous group of disorders characterized by abnormal extracellular deposition of misfolded protein fibrils. Systemic amyloidosis has an incidence of less than 10 cases per million person-years (1). Pulmonary involvement can occur in 50% of patients with amyloidosis affecting the airways, parenchyma, or pleura (2). Pulmonary amyloid may mimic “bread and butter” conditions such as infections, inflammatory lung diseases, or tumors, often leading to misdiagnosis and delayed treatment. This report describes a patient with incidental peripheral and alveolar eosinophilia and dense consolidations with biopsy-proven transthyretin amyloidosis (ATTR). A 74-year-old male with no pertinent history presented to the hospital with flank pain. Physical examination was unremarkable. Pertinent labs showed an absolute eosinophil count-0.7 × 109/L, immunoglobulin G level- 1,714mg/dL. Computed tomography of the chest showed multiple peripheral, mass-like consolidations involving all lobes. Due to progressing parenchymal abnormalities on repeat CT imaging, bronchoscopy was pursued. Bronchoalveolar lavage showed 60% eosinophils. Histopathologic examination of transbronchial biopsy showed patchy interstitial deposition of amorphous eosinophilic material and Congo red-positive tissue deposits were present. Liquid chromatography tandem mass spectrometry (LC-MS/MS) detected peptide consistent with transthyretin-type amyloid deposition with an amino acid abnormality concerning for hereditary ATTR. There are two major types of ATTR. In hereditary transthyretin amyloidosis, an aberrant amino acid sequence creates misfolded transthyretin. In wild type ATTR, misfolding of the normal transthyretin protein occurs (3). Diagnosis is confirmed by presence of apple green birefringence on Congo Red staining. Management focuses on stabilizing the abnormally formed protein. Initiating treatment depends upon the patient’s symptoms, disease severity, and patient preference. This patient’s presentation characterized by peripheral eosinophilia and imaging findings of photographic-negative pulmonary edema is atypical for pulmonary amyloidosis. Commonly, CT chest reveals nodular and diffuse alveolar-septa patterns. In this case, bronchoscopy with transbronchial biopsy played a key role in pinpointing the etiology of these multifocal infiltrates. With this powerful and accessible tool, a rare diagnosis of ATTR was established. Peng X, Wang X, Luo D, Zuo W, Yao H, Zhang W. Atypical primary pulmonary amyloidosis. Medicine 2020; 99: e20828. Zimna K, Sobiecka M, Langfort R, Blasinska K, Tomkowski W. Pulmonary amyloidosis mimicking interstitial lung disease and malignancy - A case series with a review of a pulmonary patterns. Respiratory Medicine Case Reports 2021; 33. 101427. Eggleston R, Hartman T, Walkoff Lara, Yi Eunhee, Ryu J, Baqir M. Clinical, radiologic, and pathologic features and outcomes of pulmonary transthyretin amyloidosis. Respiratory Medicine 2022; 194. 106761 This abstract is funded by: None