2.1 Lipoid Proteinosis

At least 55 mutations in the ECM1 gene have been found to cause lipoid proteinosis, a condition that results from numerous, small clumps (deposits) of proteins and other molecules that form in various tissues throughout the body. Affected individuals typically have a hoarse voice, skin abnormalities, and neurological and respiratory problems.

Typically, mutations that cause lipoid proteinosis occur in areas of the ECM1 gene known as exon 6 and exon 7. One mutation that deletes a single DNA building block (nucleotide) from exon 6 of the ECM1 gene (written 507delT) has been found in multiple individuals around the world. Another mutation that occurs in exon 7 of the gene is common in affected individuals in South Africa and results in a premature stop signal in the instructions for making the protein (written as Gln276Ter or Q276X). The ECM1 gene mutations that cause lipoid proteinosis result in the production of a nonfunctional protein or no protein at all.

A lack of functional ECM1 protein reduces binding between ECM1 and other proteins, leading to an unstable extracellular matrix. Without adequate support from the extracellular matrix, cells in the skin and other tissues are weakened. However, the cause of the deposits in skin and other tissues is not clear. The unstable extracellular matrix may cause neighboring cells to overproduce proteins and other materials. It is possible that, as these excess substances accumulate in tissues, they create the deposits characteristic of lipoid proteinosis.