Abstract
X-linked ichthyosis (XLI) is a rare X-linked dermatological condition arising from deficiency for the enzyme steroid sulfatase (STS). STS is normally expressed in the brain, and males with XLI exhibit personality differences from males in the general population, and are at increased risk of developmental and mood disorders. As the STS gene escapes X-inactivation, female carriers of XLI-associated genetic mutations have reduced STS expression/activity relative to non-carrier females, and could manifest similar behavioural phenotypes to males with XLI. Additionally, as STS activity normally increases in female tissues towards late pregnancy and into the puerperium, carrier females could theoretically present with increased rates of postpartum psychopathology. Using a worldwide online survey comprising custom-designed demographic questionnaires and multiple validated psychological questionnaires, we collected detailed self-reported information on non-postpartum and postpartum behaviour in confirmed adult (>16yrs) female carriers of genetic mutations associated with XLI (n = 94) for statistical comparison to demographically-matched previously-published normative data from female controls (seven independent studies, 98≤n≤2562), adult males with XLI (n = 58), and to newly-obtained online survey data from a general population sample of mothers from the United Kingdom and United States of America (n = 263). The pattern of results in carrier females relative to controls was remarkably similar to that previously observed in males with XLI, with evidence for increased rates of developmental and mood disorders, and elevated levels of inattention, impulsivity, autism-related traits and general psychological distress. Carrier females exhibited a significantly elevated rate of postpartum mental health conditions (notably mild depression) relative to controls which could not be accounted for by social factors. Our data confirm the psychological profile associated with XLI-associated mutations, and suggest that female carriers may be at increased risk of psychopathology, including in the postpartum period. These findings are relevant to families affected by XLI, to clinicians involved in the care of these families, and to genetic counsellors.
Highlights
X-linked ichthyosis (XLI) is a dermatological condition characterised by large, dark brown scales occurring primarily on the extensor surfaces and trunk [1]
An online survey (Survey 1) was generated using Qualtrics software to be completed by confirmed adult (>16yrs) female carriers of genetic mutations associated with XLI
A total of 104 females responded to Survey 1, 10 of whom were subsequently excluded from further analysis as their presentation was inconsistent with being a carrier for an XLI-associated mutation
Summary
X-linked ichthyosis (XLI) is a dermatological condition characterised by large, dark brown scales occurring primarily on the extensor surfaces and trunk [1]. Diagnosis of the condition is typically made on the basis of skin appearance and family history, with additional confirmatory biochemical and/or genetic analyses performed for some individuals [1]. As it arises from an X-linked mutation, XLI almost exclusively affects males: in >85% of cases of XLI, the mutation is thought to be inherited from a heterozygous carrier mother [3,4]. Prevalence rates for XLI based upon clinical samples range from 1 in 3000 to 1 in 6000 males [1], and for STS deficiency based upon prenatal screening are approximately 1 in 1500 males [5,6]. The inheritance data and prevalence rates above indicate that approximately 1 in 1200 females within the general population may be heterozygous carrier females, equivalent to ~30,000 individuals in the United Kingdom, and ~3.1million individuals worldwide
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