Lipoid proteinosis: case report and review of the literature.
Lipoid proteinosis is a rare autosomal recessive disorder, characterized histologically by infiltration of periodic acid Schiff-positive hyaline material into the skin, upper aerodigestive tract, and internal organs. Classical clinical features include skin scarring, beaded eyelid papules, and laryngeal infiltration leading to hoarseness. Moreover, the infiltrates in the tongue and its frenulum limit lingual movements and cause speech difficulties. Usually, the hoarse voice is present at birth or in early infancy, as the first manifestation. In more severe cases, diffuse infiltration of the pharynx and larynx might cause respiratory distress, at times requiring tracheostomy. The disorder has recently been shown to result from loss-of-function mutations in the extracellular matrix protein 1 gene on chromosome 1q21. The function of the protein extracellular matrix protein 1 gene is still unclear, although an important role in skin physiology and homeostasis has been hypothesized. In this report, the case is described of a 6-year-old girl with lipoid proteinosis. Histopathological examination of a laryngeal biopsy specimen showed massive deposits of eosinophilic, periodic acid Schiff-positive, and diastase resistant material in the lamina propria corroborating the clinical diagnosis of lipoid proteinosis. Molecular analyses in this patient also confirmed the clinical diagnosis. The proposita was a compound heterozygote for a new small rearrangement (543de1TG/ins15) in exon 6, and a nonsense mutation (Arg243Stop) in exon 7. Together with previously documented mutations in the extracellular matrix protein 1 gene, this study supports the hypothesis that exons 6 and 7 are the most common sites for extracellular matrix protein 1 gene mutations in lipoid proteinosis.