Ichthyosis Flashcards
Mode of inheritance in ichthyosis vulgaris?
- Autosomal semi-dominant
- Incomplete penetrance
Pathogenesis of ichthyosis vulgaris?
Loss of function mutation in filaggrin gene.
What’s filaggrin and where is it located?
It’s a filament aggregating protein.
Located in the granular layer of the epidermis
What’s the function of filaggrin?
Aggregates keratin intermediate filament & prober formation of compact squamous cells.
Water retaining amino acid (moisturizer)
What does the loss of filaggrin lead to?
- Impaired squamous cell formation.
- Trans-epidermal water loss.
- Inflammatory response upon exposure to allergens and haptens.
Most common disorder of cornification?
Ichthyosis vulgaris
Clinical features of ichthyosis vulgaris?
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.
Age at first presentation of ichthyosis vulgaris?
Infancy and early childhood & not present at birth.
Prognosis of ichthyosis vulgaris?
Usually improves with age
Associations with ichthyosis vulgaris?
Keratosis pilaris and atopic triad (asthma, hay fever, atopic dermatitis)
Pathology of ichthyosis vulgaris?
Mild orthokeratotic hyper keratosis
Diminished granular layer
Diminished filaggrin staining
Treatment of ichthyosis vulgaris?
Emollient
Urea & keratolytic preparations.
Topical retinoids (? Irritation)
Mode of inheritance in steroid sulfatase deficiency ichthyosis?
XL recessive
Pathogenesis of steroid sulfatase deficiency ichthyosis?
Deletion or inactivation mutation of STS gene on Ch xp22.3
Result of steroid sulfatase deficiency?
Impaired hydrolysis of cholesterol sulfate and DHEAS => accumulation of cholesterol 3-sulfate in epidermis => transglutaminase-1 inhibition.
What cause causes the overlap between lamellar ichthyosis and steroid sulfatase deficiency?
Transglutqminase-1 inhibition.
What is the rule of transglutaminase-1?
Important in the fermentation of the cornified envelope and epidermal barrier
Clinical picture of steroid sulfatase deficiency?
- Neonatal:
Mild erythema, generalized peeling, exfoliation of large translucent scales. - 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
Pathognomonic feature of steroid sulfatase deficiency?
Spares palms, soles, and face except pre auricular area
Associations of steroid sulfatase deficiency ichthyosis?
Asymptomatic corneal opacities
20-fold risk of cryptorchidism
Higher risk of testicular cancer and hypogonadism.
Pathology of steroid sulfatase deficiency ichthyosis?
- Hyperkeratosis or parakeratosis
- Normal or slightly thickened granular layer.
+/- follicular hyper keratosis.
EM:
Desmosomes retained and cells contain many melanosomes.
Treatment of steroid sulfatase deficiency?
Topical humectants (propylene glycol). Keratolytics and retinoids.
