Genoderms Flashcards
Peutz Jehger genetics
germ line mutations in the Serine Threonine Kinase tumor-suppressor gene found on chromosome 19p13.3 (also called STK11/LKB1).
Autosomal dominant
30% sporadic
XP genes
7 types of genes XP A - G
Life expectancy of XP
50s-60s
Ichthyosis vulgaris Epidemiology
- 1/100 - 1/200
- semi-autosomal dominant
- FLG mutation
- can be heterozygous (mild-mod) or homozygous (severe)
- more common in Caucasians
Ichthyosis vulgaris Clinical
- Heterozygous
- not clinically apparent at birth
- in infant/toddler years develop scale to extensor surfaces
- as get older, develop larger scale with adherent centres and turning out scale on this
- hyperlinear palms
- Homozygous
- 2 alleles affected
- erythematous and scaling at birth
- more severe
- scaling to forehead, cheeks, arms and legs, trunk
- Associated with atopy - allergic rhinitis, asthma and eczema
Ichthyosis vulgaris Histology
- orthokeratosis and hyperkeratosis
- absence of granular layer
- on electron microscopy there are no keratin hyaline granules or granular layer in ~ 50% cases
Ichthyosis vulgaris Treatment
- keratolytics
- emollients
- humectants
Ichthyosis vulgaris pathogenesis
- Profillagrin assists in squamous cell compaction
- It turns into filagrin, which then gets broken down to amino acids (particularly histidine) as a natural moisturiser
- Loss of this results in:
- increased cornification
- transepidermal water loss
- increased atopy
Steroid Sulfatase Deficiency epidemiology
- 1/2000 - 1/9000
- X linked recessive disorder
- Asymptomatic female carriers
- Exclusively in males
Steroid Sulfatase Deficiency pathogenesis
- Deletion of STS gene on chromosome Xp22.31
- impaired steroid sulfatase results in impaired hydrolysis of cholesterol + DHEAS resulting in cholesterol accumulation in the epidermis
- elevated cholesterol can also inhibit transglutaminase-1
Steroid Sulfatase Deficiency clinical
- Birth: lack of progression/ requires caesarean due to reduced oestrogen
- Neonate: mild erythema, generalised peeling, large translucent scale
- Childhood: dirty neck, lower legs, pre-auricular, typical polyglonal, dark-brown adherent scales
- Other:
- Corneal opacities in 10-50%
- Green colour blindness
- Cryptorchidism, testicular cancer, hypogonadism, ADHD
- Also can be associted with larger, contiguous deletion like Kallman’s
Epidermolytic Ichthyosis epidemiology
- 1/200 000 - 250 000
- Autosomal dominant with complete penetrance
- M=F
- 50% new spontaneous mutation
Epidermolytic Ichthyosis pathogenesis
- Defect in KRT1 or KRT10
- KRT1 induces palmoplantar
- Results in bad keratin alignment and filament assembly –> compromises strength and cellular integrity of the epidermis, resulting in cytolysis, acanthosis, hyperkeratosis from hyperproliferation and reduced desquamation resulting in clumping of keratin
- this results in increased TEWL and bacterial infections
Epidermolytic Ichthyosis clinical
- think ‘stinky’ and keratinocyte fragility disease
- Neonate: erythroderma, peeling, erosions, blistering, fragility - incr risk of sepsis and fluid loss
- As they get older: hyperkeratosis, blistering fades
- Flexures: ridges along the skin line
- Extensors: cobblestoning
- Palmoplantar keratoderma –> results in contractures
- Complications: infections, body odour, reduced QoL, hair loss
- Variant: epidermolytic epidermal naevi
- this is a post zygotic mutation with porcupine like streaks
- if gonadal, can pass on
- Prognosis: improves possibly after puberty - goes from generalised to localized
Epidermolytic Ichthyosis histology
- Epidermolytic hyperkeratosis, orthokeratosis, acanthosis, hypergranular layer, cytolysis of the suprabasal and granular layers –> results in an intraepidermal blister
- Keratinocyte vacuolization, dense clumps of keratin intermediate filaments
- Lymphocytic peri-vascular infiltrate
- Can diagnosis prenatally: foetal skin biopsy
Epidermolytic Ichthyosis treatment
- Neonate: ICU, fluids, antibiotics, padding, lubricants –> can heal quickly
- Older:
- Keratolytics - urea, SA, alpha hydroxy (stings)
- Tretinoin + vitamin D –> stings
- Emollients and humectants
- Mechanical abrasion
- Anti-septics
- Antibiotics
- Systemic retinoid - improves the hyperkeratosis but worsens the fragility
Superficial epidermolytic ichthyosis
- this is not a big deal
- rare autosomal dominant ichthyosis
- heterozygous mutations in KRT2 - this is in the upper most spinous and granular cell
- they just get trauma induced blisters, then hyperkeratosis develops over joints, flexures, dorsa of hands and feet
- Histo: orthokeratosis hyperkeratosis, acanthosis, granular cell layer vacuolization, occasionally results in intraepidermal separation
- Ddx: EBS
- Treatment same as EI
Superficial epidermolytic ichthyosis
- this is not a big deal
- rare autosomal dominant ichthyosis
- heterozygous mutations in KRT2 - this is in the upper most spinous and granular cell
- they just get trauma induced blisters, then hyperkeratosis develops over joints, flexures, dorsa of hands and feet
- Histo: orthokeratosis hyperkeratosis, acanthosis, granular cell layer vacuolization, occasionally results in intraepidermal separation
- Ddx: EBS
- Treatment same as EI
Colloidon Baby Causes
- Causes - SLAUGHT CENN
- Sjogren Larrson
- Lamellar ichthyosis
- Gaucher disease
- Hay-Well syndrome
- Trichothiodystrophy
- Congenital ichthyosiform erythroderma
- Netherton’s
- Neutral lipid storage disease
- 10% have milder ‘self-healing’ phenotype
- dynamic phenotype dependant on environment
- fully inactive encoded protein in utero but not after birth
Colloidon Baby Clinical
- Birth: premi, increased morbidity and mortality
- Neonat:
- taut, shiny transparent membrane like ‘plastic wrap’
- thickened
- tautness results in ectropion, eclabium, hypoplasia of nasal and auricular cartilage
- sucking impairment –> malnutrition, dehydration
- pulmonary ventilation impairment –> pneumonia
- Then membrane dries and cracks up
- Fissures –> TEWL, infection –> sepsis
- Circular bands of skin –> vascular constriction
- 2-4 weeks –> peels off in sheets and becomes underlying phenotype
Colloidon baby histology
- Thick, orthokeratotis SC
- don’t bother doing a biopsy - wait until resolved
- can do immunostain for transglut-1 in upper fermis
- can do multigene molecular testing
Colloidon baby treatment
- controlled environment
- fluid and electrolyte monitoring
- humidified incubator –> wet compresses, light emollients
- don’t mannually remove membrane, it just increases risk of infection
Colloidon baby treatment
- controlled environment
- fluid and electrolyte monitoring
- humidified incubator –> wet compresses, light emollients
- don’t mannually remove membrane, it just increases risk of infection
Lamellar ichthyosis epi, genetics, path
Epidemiology and genetics
- 1 in 200 000 - 300 000
- autosomal recessive in transglutaminase 1 - TGM1
Pre-natal diagnosis:
- CVS/amniocentesis: TGM1 gene mutation, or foetal skin biopsy at 22 weeks
Path
- TGM1 interferes with normal cross linking of structural proteins –> defective cornification and desquamation