X-linked ichthyosis

Question 1

What is the synonym for X linked ichthyosis?

Answer 1

Steroid sulfatase deficiency

Also known as steroid sulfatase deficiency.

Question 2

What is the inheritance pattern of X linked ichthyosis/steroid sulfatase deficiency?

Answer 2

X-linked recessive

The steroid sulfatase gene (STS) is located on Xp22.32.

Question 3

What is the most common mutation associated with X linked ichthyosis?

Answer 3

Gene deletions (90%)

Contiguous gene deletion syndrome accounts for 10% of cases.

Question 4

What prenatal diagnostic methods can be used for X linked ichthyosis?

Answer 4

Amniocentesis and chorionic villus sampling (CVS)

These methods include steroid sulfatase assay and analysis of maternal levels of estriol and dehydroepiandrosterone.

Question 5

What is the incidence rate of X linked ichthyosis/steroid sulfatase deficiency in males?

Answer 5

1:2,000 to 1:6,000 males

The condition typically presents between two to six weeks of age.

Question 6

What is the pathogenesis of X linked ichthyosis?

Answer 6

Steroid sulfatase gene deletion leads to decreased steroid sulfatase activity in stratum corneum with increased cholesterol sulfate and decreased cholesterol levels; may
play a role in retention hyperkeratosis
Contiguous gene deletion syndrome may result in Kallmann syndrome and X-linked
recessive chondrodysplasia punctata
Failure of labor to begin or progress in mother carrying affected fetus because of de-creased placental sulfatase and estrogen and increased fetal DHEAS

This results in increased cholesterol sulfate and decreased cholesterol levels, possibly contributing to retention hyperkeratosis.

Question 7

What are some key features of steroid sulfatase deficiency?

Answer 7

Skin, Eyes, Obstetrics, Genitourinary

Skin features include brown, adherent scales; eye features include comma-shaped corneal opacities; obstetric complications include failure of labor; genitourinary issues include cryptorchidism.

Question 8

What skin manifestation is associated with steroid sulfatase deficiency?

Answer 8

Brown firmly adherent scale, increased on extensors, posterior neck, trunk with relative sparing of flexures; sparing of palms, soles, face

Increased on extensors, posterior neck, trunk, with sparing of palms, soles, and face.

Question 9

What ocular finding is associated with steroid sulfatase deficiency?

Answer 9

Comma-shaped corneal opacities *50% of male adults, females are carriers)

Asymptomatic in 50% of adult males and some female carriers.

Question 10

What genitourinary condition is seen in 20% of patients with steroid sulfatase deficiency?

Answer 10

Cryptorchidism, with possible increase in testicular cancer

There is a possible increase in testicular cancer risk.

Question 11

What are some differential diagnoses for steroid sulfatase deficiency?

Answer 11

• Ichthyosis vulgaris
• Epidermolytic hyperkeratosis
• Lamellar ichthyosis
• Contiguous gene syndromes

These conditions may present with similar symptoms.

Question 12

What investigations are used for steroid sulfatase deficiency?

Answer 12

• Steroid sulfatase activity assay
• Lipoprotein electrophoresis
• Serum cholesterol sulfate levels

These tests help confirm the diagnosis.

Question 13

What is the management approach for steroid sulfatase deficiency?

Answer 13

• Thorough physical examination by pediatrician
• Referral to dermatologist for topical emollients
• Referral to pediatric urologist if symptomatic
• Advise obstetrician of potential complications

Management focuses on supportive care and monitoring.

Question 14

What is the prognosis for individuals with steroid sulfatase deficiency?

Answer 14

Cutaneous involvement waxes and wanes throughout life

There may be seasonal variation in symptoms.