Lipoid proteinosis.

Lipoid proteinosis is a rare autosomal recessive disorder caused by mutations in ECM1, encoding extracellular matrix protein 1, a glycoprotein expressed in many organs and which has important protein-protein interactions in tissue homeostasis. Although the disease usually presents clinically with warty infiltration of the skin and mucous membranes and a hoarse voice, neuropsychological and neuropsychiatric abnormalities are often prominent features. There may be bean- or comma-shaped intracranial calcifications, often selectively affecting the amygdala. Patients with lipoid proteinosis therefore have been used as models for demonstrating physiologic and pathologic abnormalities of the amygdala with respect to fear processing, affect and cognition, anxiety and memory. Clinically, patients may also have epilepsy, especially involving the temporal lobes. Less common or rare disease associations are headache (including migraine), ataxia, dizziness, schizophrenia, generalized dystonia, transient brachiofacial paralysis, and intracerebral hemorrhage. Beyond the foci of calcification, the cause of the neurologic abnormalities in lipoid proteinosis is unknown, although the ECM1 protein can normally bind to various extracellular matrix proteins and glycosaminoglycans as well as certain enzymes, including matrix metalloproteinase 9. Loss of key protein-protein interactions may underscore some of the disease pathophysiology. There is currently no effective treatment for lipoid proteinosis and clinical care is largely supportive.