X-Linked Recessive Ichthyosis - Diagnostic Tests

Diagnostic Tests

Histology

XRI does not have distinctive histologic features, but is associated with non-specific changes such as broadened stratum corneum and pronounced stratum granulosum.

Ultrastructural analysis

There is no clear-cut ultrastructural criterion for the diagnosis of XRI. Increased numbers of corneodesmosomes are seen in the stratum corneum. In the ruthenium tetroxide postfixation a characteristic finding is the lamellar-phase separation.

Detection of steroid sulfatase deficiency

Deficiency of arylsulfatase C (steroid sulfatase) can be directly tested in a number of tissues: placenta, fibroblasts, keratinocytes, lymphocytes and granulocytes. A radiometric/biochemical assay can be performed with lymphocytes isolated from EDTA-treated blood. A control enzyme can be determined as a positive control (e. g. leukocyte hexosamidase).

Indirect test for steroid sulfatase deficiency

Cholesterol sulphate is carried in blood by the low density (beta-lipoprotein) fraction leading to characteristic electrophoretic alterations, which can be used indirect diagnostic test for STS deficiency. There is an increased electromobility of beta-lipoprotein in XRI.

Detection of deletions on the STS locus or direct sequencing of the STS gene

Fluorescent in situ hybridization analysis can be performed to reveal deletions on the STS gene locus. If there is no such deletion standard PCR methods can be used for sequencing analysis of the STS gene.

Model Questionnaire

Here you will find the downloadable version of the ichthyosis patient form. This document is currently used to collect patient details before sending the biological sample to the diagnostic laboratory, in order to ease cellular and/or molecular investigations.

Ichthyosis patient form

Molecular Genetic Tools

Causative gene(s)

STS Genecards Logo

Mutation Database

Causative gene(s)

STS HGMD Logo