Four patients with rare diseases, such as recessive X–linked ichthyosis (RXLI, OMIM 308100), Comel–Netherton syndrome (NS, OMIM256500), monosomy 1p36 syndrome (OMIM: 607872), and a microduplication of Xp11.4 associated with extremely high levels of IgE: 7.710 kU/L, 5.300 kU/L, 1.826 kU/L, and 10.430 kU/L, respectively, were evaluated by micro– and macroarray multiplex methods. The gene discussed is IGHE; the disease is recessive X-linked ichthyosis.