Patients affected by some genetic skin defects, for example, dyskeratosis congenita or scleroderma, may present spontaneous or induced chromosomal fragility. Hence we performed a cytogenetic analysis in families of patients affected by lamellar ichthyosis, an autosomal recessive disease not yet fully characterized at the cellular and molecular levels. Chromosomal fragility was assayed in untreated lymphocyte cultures and in those supplemented with aphidicolin or bleomycin. Cells from some affected patients and some of their parents showed hypersensitivity to the radiomimetic agent bleomycin.