Beyond the Usual Suspects: Clinical and Pathological Insights From a Rare Case of Light Chain (AL) Amyloidosis in a Filipino Patient.

Systemic light chain (AL) amyloidosis is a rare, life-threatening disorder caused by the misfolding and deposition of monoclonal immunoglobulin light chains as amyloid fibrils in various organs, leading to progressive dysfunction. We report the case of a 58-year-old Filipino male who presented with a four-month history of painful paresthesia, progressive neuropathy, significant weight loss, and autonomic symptoms, including orthostatic hypotension and gastrointestinal dysmotility. Initial workup revealed a length-dependent axonal and demyelinating polyneuropathy. Chest imaging showed diffuse micronodules and lymphadenopathy, prompting further investigation. Histopathological analysis of lymph node tissue with Congo red staining confirmed amyloid deposition, while bone marrow immunohistochemistry demonstrated monoclonal kappa light chain expression and markers consistent with lymphoplasmacytic lymphoma. The patient's multisystemic involvement, including peripheral and autonomic neuropathy, exemplifies the protean clinical manifestations of AL amyloidosis and the diagnostic challenges it poses, particularly in resource-limited settings. Early recognition is crucial, as delayed diagnosis often results in irreversible organ damage and poor prognosis for those presenting with neuropathy. Treatment, adapted from multiple myeloma protocols, centers on eliminating the amyloidogenic clone using bortezomib, cyclophosphamide, and dexamethasone, although access to newer agents like daratumumab remains limited. This case underscores the need for heightened clinical suspicion, multidisciplinary collaboration, and improved diagnostic infrastructure to optimize outcomes for patients with AL amyloidosis in the Philippines and similar settings.