A new homozygous nonsense mutation in LAMA3A underlying laryngo-onycho-cutaneous syndrome

Laryngo-onycho-cutaneous (LOC) syndrome is a subtype of autosomal recessive junctional epidermolysis bullosa in which there is prominent skin and mucosal granulation tissue that can lead to delayed wound healing, laryngeal obstruction and blindness. Thus far, all cases are of Punjabi ancestry and have been shown to result from a founder mutation in the LAMA3 gene, notably involving a single nucleotide insertion mutation in exon 39, which is specific to the LAMA3A (designated exon 1 of LAMA3A) and not the LAMA3B1 or LAMA3B2 isoforms. Here, we describe a new pedigree with LOC syndrome. Affected individuals (from Iran) have the characteristic clinicopathological and molecular features of LOC syndrome: prominent granulation tissue (especially affecting the eyes), normal intensity laminin-332 immunostaining at the dermal-epidermal junction, and autosomal recessive mutations in the LAMA3A-specific exon. The pathogenic mutation is a homozygous nonsense mutation, designated p.Gln57X, which just affects the laminin-α3a transcript. These findings therefore expand the molecular basis of LOC syndrome. What's already known about this topic? Laryngo-onycho-cutaneous (LOC) syndrome is a subtype of autosomal recessive junctional epidermolysis bullosa in which there is prominent skin and mucosal granulation tissue that can lead to delayed wound healing, laryngeal obstruction and blindness. Thus far, all cases are of Punjabi ancestry and have been shown to result from a founder mutation in the LAMA3 gene, notably involving a single nucleotide insertion mutation in exon 39, which is specific to the LAMA3A (designated exon 1 of LAMA3A) and not the LAMA3B1 or LAMA3B2 isoforms. What does this study add? We describe a new pedigree with LOC syndrome. Affected individuals (from Iran) have the characteristic clinicopathological and molecular features of LOC syndrome: prominent granulation tissue (especially affecting the eyes), normal intensity laminin-332 immunostaining at the dermal-epidermal junction, and autosomal recessive mutations in the LAMA3A-specific exon. The pathogenic mutation is a homozygous nonsense mutation, designated p.Gln57X, that just affects the laminin-α3a transcript. These findings expand the molecular basis of LOC syndrome.