Background X-linked ichthyosis is a dermatological condition caused by deficiency for the enzyme steroid sulfatase. Previously, X-linked ichthyosis/steroid sulfatase deficiency has been associated with developmental and neurological phenotypes. Here, we show for the first time, that X-linked ichthyosis may be comorbid with an additional psychiatric phenotype (psychosis). Case presentation We report the case of an 11-year-old Saudi Arabian boy with X-linked ichthyosis associated with psychosis, mental retardation, autism spectrum disorder, inattentive attention deficit hyperactivity disorder, and epilepsy. Genetic analysis revealed a 1.68 Mb deletion encompassing STS in 95% of cells while biochemical analysis revealed correspondingly low steroid sulfatase activity consistent with a diagnosis of X-linked ichthyosis. The psychotic symptoms could be reasonably well controlled by administration of an atypical antipsychotic. Conclusions This report describes a case of comorbid X-linked ichthyosis and psychosis (most closely corresponding to early-onset schizophrenia) for the first time, and suggests that deficiency for steroid sulfatase and contiguous genes may increase vulnerability to psychosis as well as other psychological disorders