New insights into the pathogenesis and treatment of heavy chain deposition disease.

Heavy chain deposition disease is defined by the presence of tissue deposits of truncated monoclonal Ig heavy chains, usually associated with an underlying plasma cell clone. In this issue of Kidney International, Bridoux et al. described the clinical, histologic, and molecular characterization of 15 patients with heavy chain deposition disease, which is the largest case series to date. Notable findings included the frequent presence of C3 deposits and hypocomplementemia, the uniform finding of truncated heavy chains with the deletion in the heavy chain constant region 1, and the common occurrence of an abnormal serum-free κ:λ ratio, despite the absence of light-chain tissue deposition. Importantly, this study showed that clinical outcomes are improved significantly with modern antiplasma cell therapies such as bortezomib.