Disease: Pulmonary Amyloidosis, probably secondary

Clinical Information:

This 73 y/o white female presented with a history of increasing SOB and diffuse parenchymal lung disease on chest radiographs.Initial transbronchial biopsy showed nonspecific mild focal chronic inflammation .She was placed on colchicine therapy, but had progression of her interstitial lung disease by CXR. Repeat transbronchial biopsy was positive for congo red, consistent with pulmonary amyloidosis. Additional workup revealed a diffuse hypogammaglobulinemia, negative ANA, and elevated urine protein with sharp gamma spike (kappa light chain). She was presumed to suffer from pulmonary amyloidosis secondary to Multiple Myeloma, although she expired prior to definitive diagnosis of her light-chain disease.

Imaging:

Her CXR shows diminished lung volumes with diffuse bilateralreticulonodular opacities.

CT images reveal diffuse septalthickening with air-space opacities in both lungs. Subtle nodule formation is seen in all five lobes, but no honeycombing. This patient has mediastinal and hilar lymphadenopathy as well.

Discussion:

Amyloidosis is characterized by proteinaceous deposits in extracellular tissue and is classified into five main groups: primary, secondary, localized, familial, and senile. Any of these may affect the lungs. Lung involvement may be any of three forms: tracheobronchial, nodular, or diffuse parenchymal. More than one type will not usually coexist. Tracheobronchial amyloidosis is most common and presents as multiple nodules protruding from the wall of the trachea or bronchi, possibly causing narrowing of the lumen. Diffuse parenchymal form (also called diffuse alveolar septal) can involve both lungs diffusely or regionally with interstitial small irregular densities which may become confluent or lead to honeycombing (CXR may also be normal). This form is least common but is most likely to cause respiratory failure (as with this patient). The nodular form usually occurs in patients over 60 y/o who are generally asymptomatic until the disease is extensive. Unlike the previously mentioned forms of pulmonary amyloidosis, other organs are generally not involved. Nodules are usually peripheral, and when multiple, vary in size and shape and may calcify.

Differential Diagnosis (DDx):

DDx for the nodular type includes metastatic disease, granulomatous disease, rheumatoid, sarcoidosis, and mucoid impaction.

DDx for the diffuse parenchymal type includes idiopathic interstitial fibrosis, miliary tuberculosis, hypersensitivity pneumonitis, pnemoconiosis (especially asbestosis), rheumatoid lung, pulmonary histiocytosis X, and scleroderma.

DDx for the tracheobronchial type would include granulomatous disease, broncholith, or bronchogenic carcinoma.

References:

Graham CM, Stern EJ, Finkbeiner WE, Webb WR. High ResolutionCT appearance of diffuse alveolar septal amyloidosis.AJR 1992; 158:265-7.

Cordier JF, Loire R, Brune J. Amyloidosis of the lower respiratorytract: clinical and pathological features in a series of 21 patients.Chest 1986; 90:827-831.

Case contributed by Jill Vecchio, MD, and Debra Dyer, MD.

Debra Dyer, MD (Deb.Dyer@UCHSC.edu)