Heavy-chain diseases

This article reevaluates the heavy-chain diseases (HCDs), a condition defin ed by the presence of monoclonal immunoglobulin molecules with short heavy chains and no light chains in the patients' serum or urine. The structural and molecular abnormalities of HCD proteins and genes are first summarized and implications on the origin of HCD-producing cells are discussed. In con trast to the digestive form of ct-chain disease, which is the most frequent HCD and has a well-defined clinicopathological pattern and epidemiologic b ackground, gamma HCD represents a much more heterogeneous condition. Main c haracteristics of mu HCD, which is rare, are also described.