Maternal transmission of the 3 bp deletion within exon 7 of the STS gene in steroid sulfatase deficiency

X-linked ichthyosis: Clinical and molecular findings in 35 Italian patients

Recessive X-linked ichthyosis (XLI), the second most common ichthyosis, is caused by mutations in the STS gene encoding the steroid sulfatase enzyme. A complete deletion of the STS gene is found in 85%-90% of cases. Rarely, larger deletions involving contiguous genes are detected in syndromic patients. We report the clinical and molecular genetic findings in a series of 35 consecutive Italian male patients. All patients underwent molecular testing by MLPA or aCGH, followed, in case of negative results, by next-generation sequencing analysis. Neuropsychiatric, ophthalmological and paediatric evaluations were also performed. Our survey showed a frequent presence of disease manifestations at birth (42.8%). Fold and palmoplantar surfaces were involved in 18 (51%) and 7 (20%) patients, respectively. Fourteen patients (42%) presented neuropsychiatric symptoms, including attention-deficit hyperactivity disorder and motor disabilities. In addition, two patients with mental retardation were shown to be affected by a contiguous gene syndrome. Twenty-seven patients had a complete STS deletion, one a partial deletion and 7 carried missense mutations, two of which previously unreported. In addition, a de novo STS deletion was identified in a sporadic case. The frequent presence of palmoplantar and fold involvement in XLI should be taken into account when considering the differential diagnosis with ichthyosis vulgaris. Our findings also underline the relevance of involving the neuropsychiatrist in the multidisciplinary management of XLI. Finally, we report for the first time a de novo mutation which shows that STS deletion can also occur in oogenesis.

X linked recessive ichthyosis: Current concepts

In the present review, we describe the most important aspects of the X-linked ichthyosis (XLI) and make a compilation of the some historic details of the disease. The aim of the present study is an update of the XLI. Historical, clinical, epidemiological, and molecular aspects are described through the text. Recessive XLI is a relatively common genodermatosis affecting different ethnic groups. With a high spectrum of the clinical manifestations due to environmental factors, the disease has a genetic heterogeneity that goes from a point mutation to a large deletion involving several genes to produce a contiguous gene syndrome. Most XLI patients harbor complete STS gene deletion and flanked sequences; seven intragenic deletions and 14 point mutations with a complete loss of the steroid sulfatase activity have been reported worldwide. In this study, we review current knowledge about the disease.

Analysis of the STS gene in 40 patients with recessive X-linked ichthyosis: a high frequency of partial deletions in a Spanish population

BACKGROUND

Recessive X-linked ichthyosis (RXLI) (OMIM 308100) is a genodermatosis characterized by polygonal, dark, adherent and mild-to-moderate scales that normally improve during summer. RXLI is caused by a deficiency in steroid sulphatase (STS), whose gene has been located on the X chromosome (locus Xp22.3). Up to 90% of the mutations described in this gene are complete deletions.

OBJECTIVES

Previous reports of partial deletion of STS gene in cases of RXLI prompted us to determine the incidence of these abnormalities in a Spanish population.

METHODS

We have studied exons 1, 5 and 10 of the STS gene by polymerase chain reaction in 40 patients with clinical features of RXLI.

RESULTS

Our results revealed that 30 patients presented complete deletions (75%) while 10 patients had partial deletions (25%) a rate higher than that reported in the previous studies.

CONCLUSIONS

Amplification of exons 1, 5 and 10 is reliable in screening RXLI in the population studied here. No correlation was found between phenotype and the extent of the deletions.

Somatic and germinal mosaicism for the steroid sulfatase gene deletion in a steroid sulfatase deficiency carrier

Steroid sulfatase deficiency results in X-linked ichthyosis, an inborn error of metabolism in which the principal molecular defect is the complete deletion of the steroid sulfatase gene and flanking markers. Mosaicism for the steroid sulfatase gene has not yet been reported in X-linked ichthyosis. In this study we describe an X-linked ichthyosis patient with complete deletion of the steroid sulfatase gene and his mother with somatic and germinal mosaicism for this molecular defect. The family (X-linked ichthyosis patient, grandmother, mother, and sister) was analyzed through steroid sulfatase enzyme assay, polymerase chain reaction, DNA markers, and fluorescence in situ hybridization of the steroid sulfatase gene. Steroid sulfatase activity was undetectable in the X-linked ichthyosis patient, very low in the mother, and normal in the grandmother and sister. The X-linked ichthyosis patient showed a 2 Mb deletion of the steroid sulfatase gene and flanking regions from 5'DXS1139 to 3'DXF22S1. The mother showed one copy of the steroid sulfatase gene in 98.5% of oral cells and in 80% of leukocytes. The grandmother and sister showed two copies of the steroid sulfatase gene. The origin of the X chromosome with the deletion of the steroid sulfatase gene corresponded to the grandfather of the proband. We report the first case of somatic and germinal mosaicism of the steroid sulfatase gene in an X-linked ichthyosis carrier and propose DNA slippage as the most plausible mechanism in the genesis of this mosaicism.