30% of patients with Amyloidosis have pulmonary symptoms
Etiology
Idiopatic Amyloidosis:
Multiple Myeloma (see [[Multiple Myeloma]])
Sjogren’s Syndrome (see [[Sjogrens Syndrome]])
Rheumatoid Arthritis (see Rheumatoid Arthritis]])
Physiology
Airway or parenchymal involvement by primary or secondary amyloidosis (with protein deposited in airway)
Ig light chains are the only type of proteins that deposit to any significant extent in the lungs
Systemic amyloidosis: Ig light chain deposition in lungs, heart, GI tract, skin, kidney, skeletal muscle
Localized pulmonary amyloidosis: formation of Ig light chains by local B-cells or plasma cells (supported by observed formation of amyloid from calcitonin in medullary thyroid ca mets to lung)
Upper Airway: amyloid infiltration of vocal cords or tongue
Pathology
Nodular pattern: see below
Diffuse alveolar septal pattern: amorphous material infiltrates the interstitium and walls of pulmonary arteries, arterioles, and veins (EM reveals dense deposits in alveolar capillary BM)
Congo Red stain under polarized light: reveals characteristic “apple green” birefringence
PAS: stains alpha glycoprotein of amyloid
Diagnosis
FOB: EBB of endobronchial disease with Congo red stain reveals green birefringence under polarized light
Endobronchial plaques (usually multiple) or endobronchial papillary lesion (usually single): areas may calcify and form tracehobroncho-pathia osteoplastica/ areas may bleed severly after EBB (laser prbably is preferred)
TBB: should be performed with caution in diffuse cases (due to risk of bleeding from infiltrated vessels and factor 10 binding by amyloid/ report of fatal air embolism)
FNA: used in some cases for diagnosis, but bleeding risk is higher
CXR/Chest CT Pattern
Nodular pattern (due to mucosal large airway involvement or parenchymal macronodules): 2-4 cm nodules (sometimes <15 cm) with no lobar predilection (occasionally peripheral/occasionally cavitate/ occasionally calcified)
Extremely rare etiology of solitary pulmonary nodule
Mediastinal lymphadenopathy: may be massive and calcified in some cases (mimicking Sarcoid, NHL)
Large airway mucosal involvement
Plaques: usually present with wheezing/ fair prognosis
Papillary lesion: usually asymptomatic/good prognosis
Diffuse pattern (due to alveolar septal and pulmonary vascular involvement): diffuse interstitial infiltrates
Kerley B lines: thickened inter-lobular septa (seen at periphery of lung) due to pulmonary lymphatic obstruction
HRCT: small areas of calcification seen
Pleural effusion may be seen (although rarely without other CXR findings or associated CHF)
SPEP: positive for monoclonal gammopathy (90% of cases)
Rectal Mucosal Bx (or Abdominal SQ Fat Bx): safe and sensitive for AL type amyloid
Clinical
Pulmonary Manifestations
Nodular CXR pattern: usually asymptomatic/ good prognosis
