We analyzed the transglutaminase 1 gene locus in patients from six unrelated Italian families affected by autosomal recessive lamellar ichthyosis. In two families we identified a novel mutation (E520G) in the gene coding region, a previously reported splicing mutation (A3447G), and the mis-sense mutations S272P and V518M. The latter mutation, hitherto considered disease causing, was found to be a simple polymorphism. Linkage to transglutaminase 1 gene was excluded in two of the other four families examined. Single strand conformational polymorphism analysis of the transglutaminase 1 gene in the remaining two families did not reveal any alteration in the coding region. This finding confirms the genetic heterogeneity of the disease.