Primary AL (κ-light chain) amyloidosis manifesting as peripheral neuropathy in a young male without increase in serum and urine immunoglobulin load: A diagnostic challenge

Primary systemic or AL amyloidosis is a multisystem disorder characterized by diffuse extracellular infiltration of a fibrillar protein of monoclonal light chain origin (AL). Majority of the patients have monoclonal immunoglobulin in serum and/or urine and some have clonal proliferation of plasma cells in their bone marrow. This disease has the widest spectrum of organ involvement, most commonly affecting the kidneys, heart and liver. Involvement of peripheral nervous system is not infrequent and may be the presenting feature of the disease process. Thus, recognition of peripheral neuropathy and affecting the kidney as an early symptom of AL amyloidosis may widen the scope for therapeutic intervention. We describe here a rare case of primary amyloidosis (AL) κ-light chain presenting with clinical features of peripheral neuropathy and affecting the kidney and heart at an early age of 18 years, hitherto unreported in literature. The case was further interesting as it was not associated with increased serum/urine immunoglobulins or plasma cells in bone marrow. Diagnosis was confirmed using immuno-electron microscopy on sural nerve biopsy.