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L

Lamellar Ichthyosis

Etiology: 
 

  • 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

Etiology: 
 

  • Histo: lots of edema, eos (Reniform, kidney bean shaped grooved nuclei)

    • Stains: S100+, CD1a+, Langerin+ (forms birbeck granules)

Lentigo

Etiology: 
 

Cause: 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

Etiology: 
 

  • 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

Etiology: 
 

  • Appearance: flat, brown or black spots 

  • Tx: cryotherapy, lasers, chemical peels, and topical retinoids and hydroquinone

Leprosy

Etiology: 

Leser-Trélat sign

Etiology: 
 

Description: explosive onset of multiple seborrheic keratoses (pigmented skin lesions), often with an inflammatory base

 

Associated with: gastric adenocarcinoma 

Letterer-Siwe Disease

Etiology: 
 

Cause: 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: 
 

Cause: 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: 
 

Cause: trauma, chemotherapy, arsenic poisoning, hypoalbuminemia (Muehrcke lines), systemic disease (Terry nails)

 

Description: partial or full opacification of the nail plate

Lichen Planus

Etiology: 
 

Cause: Associated with HCV

 

Description: pruritic, purple, polygonal planar papules and plaques

 

Locations: typically, wrists and ankles  

Lichen Sclerosus

Etiology: 
 

Cause: progressive inflammatory disease

 

Description: parchment-like atrophic area that is thinner and more white

 

Associate with: SCC

Lichen Simplex Chronicus / Neurodermatitis

Etiology: 
 

Cause: hyperplasia of vulvar squamous epithelium

 

Description: leathery, thick vulvar skin that is itchy

Lichen Spinulosus

Etiology: 

Lichenoid keratosis (BLK)

Etiology: 
 

  • 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: 
 

Cause: Lightning strike injury

 

Description: transient pink-red fractal pattern marks on the skin

Lipodermatosclerosis

Etiology: 
 

bottle necking

Livedo Reticularis

Etiology: 
 

Cause: many causes, including cold exposure and chronic medical conditions (SLE, Cold AIHA, etc.)

 

Description: bluish-red, lace-like pattern

Localized Scleroderma (morphea)

Etiology: 
 

Cause: 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

Etiology: 
 

  • Histo: small pea like palisading granuloma with central casseous necrosis

Lupus pernio

Etiology: 
 

Cause: 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: 
 

Cause: 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

Etiology: 
 

Description: small, firm, translucent vesicles

 

Location: axillary folds, shoulders, neck, proximal limbs + buccal mucosa

Lymphangitis

Etiology: 
 

Cause: acute streptococcal infection of the skin

 

Description: Tender red streaks often radiate from the wound toward the nearest lymph glands

Lymphogranuloma venereum

Etiology: 
 

Cause: C. trachomatis (L1-L3)

 

Description: infection of lymphatics presenting with painless genital ulcers and painful inguinal lymphadenopathy

 

Associated with: penile SCC

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