LIGHT CHAIN DEPOSITION DISEASE: WHAT?

Abstract

TOPIC: Diffuse Lung Disease TYPE: Medical Student/Resident Case Reports INTRODUCTION: Pulmonary light chain deposition disease (PLDD) is an exceptionally rare diagnosis characterized by the deposition of nonamyloid light chains leading to progressive dyspnea and airflow obstruction. Cystic PLDD demonstrates extensive, bilateral thin-walled cysts. Pathologically, deposition of amorphous eosinophilic material surrounded by giant cell reaction that does not react Congo-Red staining is noted. Lung transplantation can be curative. CASE PRESENTATION: A 38-year-old female with past medical history of mixed connective tissue disease with lupus-like features, and long-term tobacco use was seen in the pulmonology office for worsening dyspnea on exertion and dry cough. CT-Chest showed bilateral and multiple thin-walled cysts. Pulmonary function tests were unremarkable. VEGF-D, Alpha-1-antitrypsin genotype, and HIV were unremarkable. A left upper lobe video assisted thorascopic lung biopsy was performed. Pathology was consistent with pulmonary light chain deposition disease associated with giant cell reaction and patchy lymphocytic infiltrates, without evidence of lymphoproliferative disease. There were amyloid-like nodules that did not react with Congo-Red, and staining for Pulmonary Langerhans Histiocytosis was negative.Further work-up revealed normal cell counts, kidney function, and a normal SPEP and UPEP. Free light chains and Kappa/Lambda ratio were slightly elevated. Bone marrow biopsy, FISH analysis, and karyotype were performed to rule-out a clonal process. These studies were unremarkable. She was referred to a transplant center. DISCUSSION: Light chain deposition disease is a result of monoclonal immunoglobulin deposits, and typically involves the renal, hepatic, and cardiac systems. Isolated pulmonary involvement (PLDD) is exceptionally rare, and is only a recently noted phenomenon. Cystic-predominant PLDD is characterized by extensive, bilaterally thin-walled and progressively expanding cysts that are similar in appearance to lymphangioleiomyomatosis (LAM). Clinically, PLDD is characterized by progressive dyspnea that correlates with worsening obstructive disease on PFT's. Free light chains and the Kappa/Lambda ratio are often elevated without other lab abnormalities. Surgical biopsy should be obtained, particularly if the patient has a tobacco history, as differentiating PLDD from Pulmonary Langerhans is crucial. Pathologically, PLDD is similar to amyloidosis, with amorphous eosinophilic material in cystic walls that stains positive on hematoxylin and eosin. The amorphous material is usually surrounded by giant cell reactions, and material can also be noted in airways and blood vessels. However, there is no reaction in Conge-Red staining. Treatment for PLDD is limited to lung transplantation. CONCLUSIONS: Cystic lung disease often requires surgical biopsy, particularly if rheumatologic or hematologic comorbidities are present. REFERENCE #1: Colombat M, Caudroy S, Lagonotte E, et al. Pathomechanisms of cyst formation in pulmonary light chain deposition disease. Eur Respir J 2008;32:1399-403. 10.1183/09031936.00132007 REFERENCE #2: Khawaja et al. Shedding Light on Cystic Lung Disease. The Expert Clinician. 2019. DISCLOSURES: No relevant relationships by Kaitlyn Musco, source=Web Response No relevant relationships by Dylan Soller, source=Web Response No relevant relationships by Richard Strobel, source=Web Response