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Lamellar Ichthyosis
Define: rare, inherited skin disorder characterized by the abnormal formation and shedding of skin cells, leading to thick, scale-like patches on the skin's surface
Appearance: born with a tight, shiny, and waxy collodion membrane, which peels off within the first few weeks, revealing large, dark, plate-like scales on the skin (fish-like scales)
Locations: legs + skin folds (neck + armpits)
Langerhans Cell Histiocytosis
Histo: lots of edema, eos (Reniform, kidney bean shaped grooved nuclei)
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Stains: S100+, CD1a+, Langerin+ (forms birbeck granules)
Linear IgA Bullous Dermatitis (LABD)
Tx: Dapsone
Lentigo
Etiology: sun exposure and aging
Description: Irregular-shaped tan or brown patches on the skin, usually with well-defined edges; surface can be either smooth or rough
Lentigo Maligna
Define: type of melanoma in situ characterized by slow-growing, flat, discolored patches of skin
Location: face, neck, and arms
Appearance: irregular patches that can be brown, dark brown, pink, red, white, or blue
At risk: 70+ yo
Tx: MOHs
Lentigo Simplex
Appearance: flat, brown or black spots
Tx: cryotherapy, lasers, chemical peels, and topical retinoids and hydroquinone
Leprosy / Hansen Disease
Etiology: Mycobacterium leprae complex
Types/Appearance:
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Paucibacillary/Tuberculoid Hansen disease = < 5 lesions = hypo or hyperpigmented macules with loss of sensation
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Multibacillary/Lepromatous Hansen disease = 6+ lesions = diffuse, symmetrical, infiltrative skin papules + plaques with dermal thickening; not always loss of sensation
At risk: immigrants, exposure to armadillos
Tx: PB = dapsone + rifampin for 12 mo; MB = dapsone + rifampin + clofazimine for 24 mo
Leser-Trélat sign
Description: explosive onset of multiple seborrheic keratoses (pigmented skin lesions), often with an inflammatory base
Associated with: gastric adenocarcinoma
Letterer-Siwe Disease
Etiology: unknown cause, but the number of Langerhans cells in the skin and other organs are triggered to increase (type of Langerhans cell histiocytosis); BRAF V600E mutation associated
Description: small pinkish papules or blisters that may be crusted or infected (appears like seborrheic dermatitis)
At risk: <2 yo
Location: scalp, neck, armpits, groin, and trunk
Leukocytoclastic Vasculitis / hypersensitivity vasculitis / hypersensitivity angiitis
Etiology: allergic reaction to drugs, Streptococcal URTI, infection from HBV, HCV, S. aureus, mycobacterium, and autoimmune disorders (RA, SS, SLE, HSP)
Description: grouped rash on legs that include pustules, nodules, and mottling
Leukonychia
Etiology: trauma, chemotherapy, arsenic poisoning, hypoalbuminemia (Muehrcke lines), systemic disease (Terry nails)
Description: partial or full opacification of the nail plate
Lichen Planus
Description: pruritic, purple, polygonal planar papules and plaques
Locations: typically, wrists and ankles
Associated with: HCV
Lichen Sclerosus
Etiology: progressive inflammatory disease
Description: parchment-like atrophic area that is thinner and more white
Associated with: SCC
Lichen Simplex Chronicus / Neurodermatitis
Etiology: hyperplasia of vulvar squamous epithelium
Description: leathery, thick vulvar skin that is itchy
Lichen Spinulosus
Etiology:
Lichenoid keratosis (BLK)
Appearance: single, small, pink or reddish papule or plaque; can appear as a wart-like growth or a scaly, dry patch; shiny at first, take an alcohol wipe, will be dull appearance afterwards
Vs. BCC will still be shiny afterwards
Locations: trunk and upper extremities
Tx: cryo, EDC
Cause: unknown cause, but triggers include minor trauma such as friction, drugs, dermatitis, and sun exposure
Description: single small gray-brown or inflamed plaque or papule
Location: chest + upper extremities
Lichtenberg Figures
Etiology: Lightning strike injury
Description: transient pink-red fractal pattern marks on the skin
Lipodermatosclerosis
bottle necking
Lipomas
painless
Vs. angiolipomas are painful
Livedo Reticularis
Etiology: many causes, including cold exposure and chronic medical conditions (SLE, Cold AIHA, etc.)
Description: bluish-red, lace-like pattern
Localized Scleroderma (morphea)
Etiology: unknown
Description:
1. active stage = inflammatory erythematous plaque
2. sclerosis stage = yellow-ivory lesion
3. atrophy = cigarette-like paper
Associated with: other autoimmune conditions
Lupus Miliaris Disseminated Faciei
Histo: small pea like palisading granuloma with central casseous necrosis
Lupus pernio
Etiology: Sarcoidosis
Description: blue red to violet smooth shiny nodules + plaques
Location: head + neck, especially nose, ears, lips, cheeks
At risk: African American females
Lyme Disease / Erythema Migrans
Etiology: Borrelia burgdorferi (via Ixodes deer tick)
Description: bull’s eye configuration that typicaly appears 7–14 days (range 3–33 days) after the infected tick bite
At risk: living in the northeast
Lymphangioma circumscriptum
Description: small, firm, translucent vesicles
Location: axillary folds, shoulders, neck, proximal limbs + buccal mucosa
Lymphangitis
Etiology: acute streptococcal infection of the skin
Description: Tender red streaks often radiate from the wound toward the nearest lymph glands
Lymphogranuloma venereum
Etiology: C. trachomatis (L1-L3)
Description: infection of lymphatics presenting with painless genital ulcers and painful inguinal lymphadenopathy
Associated with: penile SCC