Chapter 6 Flashcards
(123 cards)
ichthyosis vulgaris mutation/inheritance
filaggrin mutation–defective/abnormal synthesis of filaggrin, AD inheritance
ichthyosis vulgaris clinical
starts few months after birth, large adherent scales on extensor surfaces of extremities (fish scales). smaller scales on other surfaces. Spares flexural creases. +KP, HK on palms/soles
ichthyosis vulgaris acquired variant
- pts with lymphoma (Hodgkins), carcinoma, or sarcoid.
- decreased expression of profilaggrin likely 2/2 instability of its mRNA (small, but normal k-h granules–reduced, but normal synthesis)
ichthyosis vulgaris path
- moderate HK with thin or absent granular layer
- HK extends into hair follicles–>large keratotic follicular plugs
- normal dermis
- normal epidermal proliferation (with tritiated thymidine)
- “retention keratosis from increased adhesiveness of SC”
ichthyosis vulgaris EM
- k-h granules appear small and crumby or spongy due to defective synthesis
- s. granulosum is only a single layer
X-linked ichthyosis inheritance/genetics
- x-linked recessive. 90% gene deletion
- absence of steroid sulfatase activity
X-linked ichthyosis clinical
rarely present at birth. female carriers are frequently affected, but men have more severe.
-scale thickness increases in childhood
+involvement of flexural creases
X-linked ichthyosis path
- hk with normal or slightly thickened granular layer
- slightly thickened epidermis
- normal epidermal proliferation (with tritiated thymidine)
- “retention hk from delayed dissolution of desmosomal disks in horny layer”
steroid sulfatase role in x-linked icthyosis
- deleted in x-linked icthyosis
- usually removes cholesteryl sulfate (made by Odland bodies) which provides cell cohesion in the lower stratum corneum
- without STS, cells stay stuck together and can’t normally desquamate
epidermolytic hyperkeratosis (EHK) inheritance
-AD
EHK synonym
bullous congenital ichthyosiform erythroderma
epidermolytic hyperkeratosis (EHK) clinical
- starts few days after birth
- thick brown verrucous scaling
- flexural surfaces with furrowed hk
- vesicles and bullae and erosions only in first few years
epidermolytic hyperkeratosis (EHK) path
- “epidermolytic hk” or “granular degeneration”
- clear spaces around nuclei in upper stratum spinosum and in stratum granulosum
- peripheral to clear spaces, cells have indistinct boundaries formed by lightly staining material or by k-hg’s
- thickened granular layer with irregularly shaped khg’s
- compact hk
- bullae are intrapidermal
- upper dermis with mod-severe chronic inflammatory infiltrate
- 5x the number of normal mitotic figures
epidermolytic hyperkeratosis (EHK) pathogenesis/genetics
- defects in KRT1 an KRT10
- excessive production of tonofilaments
- excessive and premature khg formation (get embedded in thick shells of irreg tonofilaments)
- desmosomal/tonofilament binding disturbed, so see desmosomes that only attach to one kc–>blisters
- increased proliferative activity of epidermis (see with tritiated thymidine)
Autosomal recessive ichthyosis 2 subtypes–clinical
1) congenital ichthyosiform erythroderma:
- less severe
- fine white scales, significant erythroderma, improves with puberty
2) lamellar ichthyosis
- large, platelike scales, severe ectropion, only miild erythroderma
+palms/soles, flexural surfaces involved in both
Autosomal recessive ichthyosis genetics/pathogenesis
heterogeneous from family to family
- transglutaminase 1 (TGM1) deleted
- mutation in ABCA12
- storage of neutral lipid in multiple tissues (Chanarin-Dorfman syndrome) -see lipid vacuoles in leukocytes
CHILD syndrome clinical
- starts at birth
- unilateral ichthyosiform erythroderma
- ipsilateral underdevelopment of limbs
CHILD syndrome mnemonic
Congenital Hemidysplasia with Ichthyosiform erythrodermal and Limb Defects
CHILD syndrome genetics
- x-lined dominant defect–lethal in hemizygote maale fetus
- all cases females
CHILD syndrome pathogenesis
- peroxisomes abnormal in fibroblasts
- mutations in genes encoding enzymes that convert lanosterol to cholesterol
CHILD syndrome path
- thickened epidermis
- pronounced hk
- prominent parakeratotic foci
Harlequin ichthyosis clinical/inheritance
- usually fatal
- starts at birth-thick, horny cuirass (armor) with deep fissures
- marked ectropion, eclabium
- AR inheritance
Harlequin ichthyosis path
- massive hk (SC 25-30x thicker than malpighii (basal+spinosum)
- granulosum-normal to flattened to absent
- small droplets of neutral fat uniformly throughout SC
- areas of parakeratosis
Harlequin ichthyosis genetics
- deletion mutation of ABCA12
- abnormal lamellar body formation and secretion
- inadquate delivery of desmosomal proteases to SC
- failure to degrade corneodesmosomes