Intracellular extraocular muscle light- and heavy-chain deposition disease contributing to compressive optic neuropathy in a patient with preexisting Graves' orbitopathy.

PURPOSE Light- and heavy-chain deposition disease (LHCDD) is a rare form of nonamyloidal monoclonal immunoglobulin deposition disease (MIDD) in which light- and heavy-chain immunoglobulin fragments accumulate systemically, typically leading to end organ dysfunction. Herein we describe the case of a 64-year-old female with a history of Graves' orbitopathy and multiple myeloma who presented with bilateral asymmetric compressive optic neuropathies. PROCEDURE A biopsy of the right medial rectus muscle was taken during orbital decompression surgery. RESULTS Light and electron microscopy of the biopsy specimen led to a diagnosis of intracellular skeletal muscle LHCDD. CONCLUSION This is the first published report to describe the findings of: (1) intracellular deposition of nonamyloidal MIDD; (2) orbital involvement of nonamyloidal MIDD, and (3) compressive optic neuropathy resulting from any form of MIDD.