Ichthyosis

Question 1

Mode of inheritance in ichthyosis vulgaris?

Answer 1

• Autosomal semi-dominant

- Incomplete penetrance

Question 2

Pathogenesis of ichthyosis vulgaris?

Answer 2

Loss of function mutation in filaggrin gene.

Question 3

What’s filaggrin and where is it located?

Answer 3

It’s a filament aggregating protein.

Located in the granular layer of the epidermis

Question 4

What’s the function of filaggrin?

Answer 4

Aggregates keratin intermediate filament & prober formation of compact squamous cells.

Water retaining amino acid (moisturizer)

Question 5

What does the loss of filaggrin lead to?

Answer 5

1. Impaired squamous cell formation.
2. Trans-epidermal water loss.
3. Inflammatory response upon exposure to allergens and haptens.

Question 6

Most common disorder of cornification?

Answer 6

Ichthyosis vulgaris

Question 7

Clinical features of ichthyosis vulgaris?

Answer 7

Find white Flaky scales on the extensors extensor surfaces of the extremities with palmar /planter hyper linearity.

Sparing the groin and flexural areas.

Scales have adherent center and detach out toward turning edges.

Question 8

Age at first presentation of ichthyosis vulgaris?

Answer 8

Infancy and early childhood & not present at birth.

Question 9

Prognosis of ichthyosis vulgaris?

Answer 9

Usually improves with age

Question 10

Associations with ichthyosis vulgaris?

Answer 10

Keratosis pilaris and atopic triad (asthma, hay fever, atopic dermatitis)

Question 11

Pathology of ichthyosis vulgaris?

Answer 11

Mild orthokeratotic hyper keratosis
Diminished granular layer
Diminished filaggrin staining

Question 12

Treatment of ichthyosis vulgaris?

Answer 12

Emollient
Urea & keratolytic preparations.
Topical retinoids (? Irritation)

Question 13

Mode of inheritance in steroid sulfatase deficiency ichthyosis?

Answer 13

XL recessive

Question 14

Pathogenesis of steroid sulfatase deficiency ichthyosis?

Answer 14

Deletion or inactivation mutation of STS gene on Ch xp22.3

Question 15

Result of steroid sulfatase deficiency?

Answer 15

Impaired hydrolysis of cholesterol sulfate and DHEAS => accumulation of cholesterol 3-sulfate in epidermis => transglutaminase-1 inhibition.

Question 16

What cause causes the overlap between lamellar ichthyosis and steroid sulfatase deficiency?

Answer 16

Transglutqminase-1 inhibition.

Question 17

What is the rule of transglutaminase-1?

Answer 17

Important in the fermentation of the cornified envelope and epidermal barrier

Question 18

Clinical picture of steroid sulfatase deficiency?

Answer 18

1. Neonatal:
   Mild erythema, generalized peeling, exfoliation of large translucent scales.
2. Infancy:
   Typical polygonal dark brown adherent scales.
   Symmetrically on extremities, trunk, neck “dirty neck appearance”

NB:
Palms, soles and face spared
Fine scales of scalp during childhood diminish overtime

Question 19

Pathognomonic feature of steroid sulfatase deficiency?

Answer 19

Spares palms, soles, and face except pre auricular area

Question 20

Associations of steroid sulfatase deficiency ichthyosis?

Answer 20

Asymptomatic corneal opacities

20-fold risk of cryptorchidism

Higher risk of testicular cancer and hypogonadism.

Question 21

Pathology of steroid sulfatase deficiency ichthyosis?

Answer 21

1. Hyperkeratosis or parakeratosis
2. Normal or slightly thickened granular layer.
   +/- follicular hyper keratosis.

EM:
Desmosomes retained and cells contain many melanosomes.

Question 22

Treatment of steroid sulfatase deficiency?

Answer 22

Topical humectants (propylene glycol). 
Keratolytics and retinoids.