Ichthyosis, X-Linked

Alternative Names

  • XLI
  • Steroid Sulfatase Deficiency
  • STS Deficiency
  • Placental Steroid Sulfatase Deficiency
  • Steroid Sulfatase Deficiency Disease
  • SSDD

Associated Genes

Steroid Sulfatase
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WHO-ICD-10 version:2010

Congenital malformations, deformations and chromosomal abnormalities

Other congenital malformations

OMIM Number

308100

Mode of Inheritance

X-linked recessive

Gene Map Locus

Xp22.31

Description

X-linked ichthyosis is considered one of the five main types of ichthyosis.  It is the second most common type of ichthyosis, with an estimated prevalence of 1 in 6,000 births.  The condition can range from mild to severe, and almost occurs only in males.  Onset may occur within the first days of life with features that include generalized, fine or rhomboid, adherent, dark brown or light grey, scaling of the skin. It is also associated with corneal opacities of the eye, undescended testicles and neurological abnormalities. 

Diagnosis is based mainly on family history and clinical findings, and can be confirmed by biochemical analysis, typically, serum protein electrophoresis, steroid sulfatase (STS) activity test of fibroblasts or leukocytes, and molecular/cytogenetic analyses, including polymerase chain reaction, and/or fluorescent in situ hybridization.  There is no definitive treatment for XLI.  Management typically involves hydrating and softening the skin with the use of lubricating bath oils and emollients containing humectants and keratolytics to improve scaling of the skin and to improve the appearance of the skin.

Molecular Genetics

Mutations or deletions in the steroid sulfatase STS gene (Xp22.3) are the cause of recessive X-linked ichthyosis.  The STS gene encodes a lipid hydrolase of the stratum corneum that participates in the regulation of permeability barrier homeostasis and desquamation by catalyzing the hydrolysis of steroid sulfates.  STS deficiency leads to accumulation of cholesterol sulphate in the outer layer of the skin leading to a dysfunctional skin barrier and retention of the outer skin cells causing the typical scaling.  Approximately 90% of X-linked ichthyosis patients have large deletions involving the entire STS gene and flanking regions.

Epidemiology in the Arab World

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Other Reports

Iraq

Ben-Rebeh et al. (2012) reported an Iraqi patient with X-linked Ichthyosis. Molecular analysis revealed the deletion of the entire STS gene.   

Saudi Arabia

Al Jasmi and Al-Khenaizan (2002) described a 5-year old male child diagnosed with XLI. He had a left undescended testes. A brother was also affected with dermatological changes. Parents were consanguineous. 

Al-Zayir and Al-Amro (2004) conducted a study between January 1990 and December 1995 to document the clinical and epidemiological features of patients with primary hereditary ichthyosis (PHI) in Saudi Arabia.  Out of 10455 dermatology patients; a total of 71 patients (44 males and 27 females) were diagnosed with PHI.  Consanguinity among the parents of the patients was significantly high (85%); parents of 60 of the 71 patients were married to either first-degree relatives or to second-degree relatives.  Fifty-three of the 71 patients had positive family history of PHI.  X-Linked Recessive Ichthyosis was diagnosed in 16.9% of the patients.

 

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