Summary Background X‐linked recessive ichthyosis (XLI) is a relatively common type of ichthyosis caused by a deficiency in the steroid sulfatase (STS) enzyme. It is the only type of ichthyosis that can be both syndromic and nonsyndromic. Typical clinical features include dark‐brown scale of variable size favouring the extensor surfaces of the extremities. Objectives To characterize clinically nonsyndromic XLI, with a particular focus on extracutaneous manifestations. Methods This was a multicentre retrospective review of clinical findings from a case series of patients with a clinical and genetic diagnosis of XLI. Results We identified 30 patients with XLI belonging to 25 different families carrying a deletion in the STS locus. All patients had dark scales of variable size on the extensor surfaces of the extremities. Lack of flexural involvement and pruritus were common but inconsistent findings, whereas palmoplantar hyperlinearity was absent in all but one patient. A history of orchiopexy was present in 10% and thus was more common than expected vs. the general population (3%). Neurological disorders including epilepsy (13%) and attention deficit hyperactivity disorder (ADHD; 30%) were over‐represented in patients with XLI. Conclusions This was a retrospective study with a limited number of patients. In the absence of confirmatory genetic testing and family history of the disease, dark‐brown scale of the extensor surfaces and the absence of palmoplantar hyperlinearity appear to be the most reliable clinical findings supporting a diagnosis of XLI. Dermatologists should be aware of the high prevalence of ADHD and epilepsy in patients with nonsyndromic XLI. What's already known about this topic? Nonsyndromic X‐linked recessive ichthyosis is a relatively common type of ichthyosis. Prior studies found a high prevalence of cryptorchidism and attention deficit hyperactivity disorder (ADHD). What does this study add? We identified a high prevalence of epilepsy (13%), confirmed a high frequency of ADHD (30%) and found a 10% prevalence of orchiopexy. We also quantified other common findings such palmoplantar hyperlinearity (almost always absent) and pruritus (present in 60% of patients). Linked Comment: Traupe. Br J Dermatol 2018; 179:821–822. Plain language summary available online Respond to this article