(mouse Lect2 consists of two varieties a typical 151 amino acid protein and an atypical 132 amino acid protein). Its structure is similar to that of the M23 family of metalloendopeptidases. Unlike this family of peptidases, however, LECT2 has not been found to possess enzymatic activity and does not appear to share any functions with M23 metalloendopeptidases. LECT2 protein is widely expressed in vascular tissues, smooth muscle cells, adipocytes, cerebral neurons, apical squamous epithelia, parathyroid tissues, the epithelial cells of sweat and sebaceous glands, Hassall bodies, and monocytes. When these cells or tissues are subjected to inflammatory, fibrotic, and other insults, they commonly reduce their expression of LECT2. The liver hepatocyte is considered to be the source of the LECT2 circulating in blood. However, its expression in these cells is extremely low or undetectable even though these cells express very high levels of LECT2 mRNA. This implies that hepatocytes secrete LECT2 almost immediately after they make it. Using very sensitive methods, LECT2 protein can also be detected at low levels in the endothelial cells of hepatic arteries and veins including central veins. Several cell types or tissues, e.g. osteoblasts, chondrocytes, cardiac tissue, gastrointestinal smooth muscle cells, and epithelial cells of some tissues normally do not express LECT2 but do so under a variety of disease conditions. Disease associations LECT2 amyloidosis LECT2 amyloidosis (ALECT2) was the third most common (~3% of total) cause of amyloidosis in a series of >4,000 individuals studied at the Mayo Clinic in the United States. However, LECT2 amyloidosis has a strong ethnic bias, afflicting particularly Mexicans and to a lesser extent, non-Mexican Hispanics. Hispanics made an important contribution to the Mayo Clinic's rate of LECT2 amyloidosis. LECT2 amyloidosis also has an increased incidence in Punjabis, South Asians, First Nations people of British Columbia, Native Americans, and Egyptians. In Egyptians, LECT2 is second most common cause of renal amyloidosis, accounting for nearly 31% of all cases. LECT2 amyloidosis is likely to be a far less common cause of systemic amyloidosis in populations containing fewer numbers of individuals of the cited ethnic groups. On the other hand, LECT2 amyloidosis represents an important but at present very much under-recognized cause of chronic kidney disease in the cited ethnic groups and, possibly, other ethnic groups yet to be determined. It has been found repeatedly that the mere presence of LECT2 amyloid tissue deposits does not necessarily indicate the presence of