Heavy Chain Disease, also known as hcd, is related to gamma heavy chain disease and alpha chain disease. An important gene associated with Heavy Chain Disease is IGHG3 (Immunoglobulin Heavy Constant Gamma 3 (G3m Marker)), and among its related pathways/superpathways is Cell surface interactions at the vascular wall. Affiliated tissues include b cells and small intestine, and related phenotypes are immune system and hematopoietic system