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12 Cards in this Set

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Clinical EHK/BCIE/BI
Clinical EHK/BCIE/BI
Inheritance
Autosomal dominant; 50% spontaneous mutations; keratin K1, K1 0 genes on 12q, 1 7q respectively
Prenatal
Fetal skin biopsy at 20 to 22 weeks clumped keratin filaments on electron
microscopy
DNA analysis: K1 and K1 0 mutations if defect in family known, linkage analysis if kindred is large
Incidence
Rare approximately 3,000 Americans afflicted; M=F
Age @P
Birth
Pathogenesis
Heterogeneous gene defects in K1, K1 0 leads to defective keratin filaments in the upper epidermis with subsequent tonofilament clumping and bullae formation; arg res 156 of K1 0 is most common site for mutation with greatest severity at terminal rod regions Extensive epidermal nevi (ichthyosis hystrix) reflect a somatic mosaicism for KI /K1 0 mutations; if gonadal mosaicism, then may have offspring with fullblown epidermolytic hyperkeratosis
Clinical
Skin

Newborn
Widespread bullae, erythroderma, denuded skin; secondary sepsis, electrolyte imbalance; ± focal areas of hyperkeratosis Later Infancy to

Adulthood Localized to generalized hyperkeratosis with rare, focal bullae secondary to infection (Staphyloccus aureus, gram negative bacteria); dark, warty scales with spiny ridges, increased in flexures; secondary bacterial infection with foul odor in macerated, intertriginous areas; scales shed with full thickness stratum corneum leaving tender, denuded base; prominent palmoplantar keratoderma (in some patients); secondary nail dystrophy
D/Dx
Newborn
Epidermolysis bullosa (p. 200) Staphylococcal scalded skin syndrome
Toxic epidermal necrolysis
Other causes of blistering
Later Infancy to Adult
Otherichthyoses
Lab
Skin biopsy for hernatoxylin and eosin (H&Q, frozen section (in newborn), and electron micro
Bacterial culture
Manage
Newborn
Transfer to neonatal intensive care unit monitor fluid, electrolytes, sepsis workup; intravenous (IV) broad spectrum antibiotics until cultures negative; gentle handling, protective isolation

Later Infancy to Adulthood Avoid topical keratolytics, salicylic acid, corticosteroids; systemic retinoids short course in adulthood for flares; emolliation; antistaphylococcal, gram negative antibiotic coverage; antibacterial soaps Betadine, Chlorhexicline, Clorox in bath
Prognosis
Widespread blistering clears after newborn period; hyperkeratotic scale usually lifelong; generalized involvement may improve to localized disease after puberty