Ichthyosis x-linked recessive Q80.1

X-linked recessive ichthyosis due to mutation in the steroid sulfatase gene (almost exclusively affecting the male sex). Rarely collodion skin at birth. Disease symptomatology is often present at birth or breaks out in the first months of life. The course is progressive until puberty and then remains stationary.

Worldwide & panethnic distribution. Incidence: 1/2000-6,000 male births. Prevalence in the general population is 1:4,000.

X-linked recessive mutations of the steroid sulfatase gene(STS gene; gene locus: Xp22.3). The gene defect is a deletion of the STS gene in 90%. This leads to a deficiency of microsomal steroid sulfatase, an enzyme that removes sulfate residues from cholesterol sulfate and dehydroepinandrosterone. This leads to an increase of cholesterol sulfate in keratinocytes, fibroblasts and leukocytes. Gene mutation may also extend to adjacent genes, leading to more complex disease associations.

• XRI + Kallmann syndrome
• XRI + X-linked recessive form of chondrodysplasia punctata
• XRI+ recessive epidermolysis bullosa dystrophica (Hernández-Martín A et al. 2010).
• XRI + cryptorchidism (20% of cases)
• XRI + ADHD (in 20-30% of cases of XRI patients)
• XRI + autism (25% of cases)

Beginning in infancy with relatively light scales first on the lower legs. In comparison to the autosomal dominant ichthyosis vulgaris the scaling is stronger, the skin scales themselves are larger and relatively firmly attached. With increasing age, the scaling becomes darker, more adherent and later is dirty grey, thick and coarse-fielded, rhombic. The large body flexor folds are mostly recessed, just like in the autosomal dominant form. The palms of the hands and soles of the feet do not show any increased line drawing. Comma-shaped, deep-seated corneal opacities are frequent. The accumulation of birth complications is also striking. In addition, about one in five patients has an undescended testicle (cryptorchidism).

The activity of the enzyme steroid sulfatase can be determined by a blood test, making this ichthyosis the only one to date that can be reliably detected by a simple blood sample.

Increase of cholesterol sulfate (approx. 10 times normal value) in blood cells and serum. Cholesterol in serum is decreased up to 50%.

Lipoprotein electrophoresis: Increased mobility of HDL and VLDL.

Retention hyperkeratosis with preserved, slightly widened stratum granulosum, distinct papillomatosis, 10-fold thickened interfollicular orthohyperkeratotic stratum corneum.

Electron microscopy: decreased number of keratinosomes.

• Adults: Initial 10-35 mg/day for 4 weeks, lowest possible maintenance dose after clinic (10-50 mg/day)
• In children, acitretin therapy only under strict consideration of benefit and risk: initial 0.5 mg/kg bw/day, maintenance dose: 0.1-0.2 mg/kg bw/day.

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