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P

Paget disease

Etiology: 
 

Cause: DCIS

 

Description: erythematous, pruritic, ulcerated skin at the nipple and breast

Palmoplantar Verruca

Etiology: 
 

  • Appearance: thick, endophytic papules

Papillary Hidradenoma / Hidradenoma Papilliferum

Etiology: 
 

Cause: unknown cause; thought to arise from anogenital mammary-like glands

 

Description: slow-growing painless, firm, flesh to red nodule 

 

Location: labia majora + interlabial folds

Papillon-Lefure Syndrome

Etiology: 
 

  • Appearance: hyperhidrosis + periodontitis with severe gingivitis

  • Inheritance: AR

Peau d’orange

Etiology: 
 

Cause: blockage of lymphatic drainage with or without associated stromal infiltration; inflammatory breast cancer

 

Description: thick and pitted, with a texture and appearance similar to that of orange peel

Pemphigoid gestationis

Etiology: 
 

  • Appearance: 

  • Sx: started in 2nd and 3rd trimester, intensely pruritic urticarial papules and plaques/vesicles/bullae

  • Location: 50% involve umbilicus

  • Dx: skin bx with H&E and IF

  • Tx: topical anti-inflammatory

  • RF: preterm delivery

  • Cause: production of autoantibodies to proteins found in the skin 

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  • Description: intensely itchy urticaria-like rash during mid to late pregnancy (13–40 weeks gestation); initially itchy red bumps are around the belly button

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  • Associated with: pregnancy, postpartum, Grave’s Disease

Pemphigus Foliaceus

Etiology: 
 

Cause: IgG antibodies against only desmoglein-1 causing acantholysis in granular layer of epidermis 

 

Description: superficial blisters 

 

Location: torso + spread to face + scalp

Pemphigus Vulgaris

Etiology: 
 

  • Appearance: erosions or flaccid bullae 

  • At risk: middle aged to young adults

  • Cause: IgG antibodies against desmoglein-1 and or desmoglein-3 causing suprabasilar acantholysis

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  • Description: numerous flaccid intraepidermal bullae (typically ruptured) that also involve oral mucosa

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  • At risk: Ashkenazi Jewish or Mediterranean descendants

Periorificial Dermatitis

Etiology: 
 

  • Tx: taper steroids, oral tetracycline, topical metronidazole, erythromycin, tacrolimus

Petechiae

Etiology: 
Description: Tiny 1-2 mm, initially purpuric, non-blanchable macules resulting from tiny hemorrhages

Peutz-Jeghers Syndrome (PJS)

Etiology: 
 

Cause: autosomal dominant condition with mutations in serine/threonine kinase 11 (STK11) 

 

Description: Tan, dark brown, or bluish black flat patches 1 to 5 mm in size

 

Location: around the mouth, lips, gums, inner lining of the mouth, eyes, hands and feet, fingers and toes, anus and genital areas

 

Associated with: GI polyps

Piebaldism

Etiology: 
 

  • Define: rare, inherited genetic disorder characterized by patches of skin and hair that lack pigment 

  • Cause: AD mutation inactivating c-KIT gene

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  • Description: white forelock with white patches of skin 

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  • Location: face (chin), trunk, + distal extremities

Pigmentary Demarcation Line

Etiology: 
 

  • Define: abrupt transition between areas of darker and lighter pigmentation

  • At risk: darker skin tones

Pigmented DFSP (Bednar tumor)

Etiology: 
 

  • At risk: AA 

Pigmented Purpuric Dermatosis (PPD)

Etiology: 
 

  • Appearance: reddish-brown patches and spots

  • Etiology: results from capillary inflammation and leakage of red blood cells, leading to hemosiderin deposits

  • Location: lower legs

  • Tx: topical corticosteroids, compression stockings

Pilar Cyst / Trichilemmal Cyst

Etiology: 
 

Cause: keratin-filled cyst that originates from the outer hair root sheath; typically running in families (AD)

 

Description: one or more firm, mobile, subcutaneous nodules measuring 0.5 to 5 cm in diameter and without a central punctum

 

Location: typically scalp

Pilomatricoma

Etiology: 
 

  • Define: benign (non-cancerous) skin tumor that arises from hair follicle cells

  • Appearance: small, hard, and slow-growing lump 

  • Location: head or neck

Pityriasis Alba

Etiology: 
 

Cause: unknown; coexists with dry skin and atopic dermatitis

 

Description: hypopigmented patches that are round or irregular in shape and up to 5 cm in diameter

 

Locations: typically appear on face, especially cheeks and chin

Pityriasis Rosea

Etiology: 
 

Cause: viral infection

 

Description: begins with a single, primary, 2- to 10-cm herald patch / mother patch that appears on the trunk or proximal limbs; eruption of small oval papules follows within 1-2 weeks and disappears around 6 weeks

Pityriasis (Tinea) Versicolor

Etiology: 
 

Cause: Malassezia furfur

 

Description: small hypo and hyperpigmented macules 

 

Location: trunk, face, shoulders, neck

Pitysporum Folliculitis

Etiology: 
 

  • Dermatoscope: spores grouped together in hair follicle

POEMS Syndrome

Etiology: 
Description: hyperpigmentation, hemangiomas, hypertrichosis, and scleroderma-like skin thickening

Polyarteritis Nodosa (PAN)

Etiology: 
 

Cause: Medium vessel vasculitis

 

Description: lace like rash (livedo reticularis) + ischemic digits

 

Associated with: HBV, acute mesenteric ischemia 

Polymorphic Eruption of Pregnancy (PEP) / Pruritic Urticarial Papules and Plaques of Pregnancy (PUPPP)

Etiology: 
 

  • Sx: onset of late 3rd trimester

  • Location: starts within abdominal striae with periumbilical sparing

  • RF: primigravid preg, multiple gestation preg

  • Does not affect development

  • Tx: topical steroids, non-sedating oral antihistamines, oral pred

Polymorphous Light Eruption (PMLE)

Etiology: 
 

  • Appearance: erythematous papules, vesicles, plaque on sun exposed skin only

  • Tx: antihistamines (Zyrtec and Benadryl), steroid injection in office

  • Cause: stretching of the skin elicits an immune response due to connective tissue damage

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  • Description: itchy, bumpy rash that starts in the stretch marks of the abdomen

Porphyria Cutanea Tarda

Etiology: 
 

Cause: AD mutation in UROD gene = affecting uroporphyrinogen decarboxylase = accumulates uroporphyrin

 

Description: blistering cutaneous photosensitivity and pigmentation

Port-wine stain / Nevus flammeus

Etiology: 
 

Cause: mutation in the GNAQ gene on chromosome 9q21

 

Description: sharply demarcated deep red macule or patch, typically unilateral, becomes nodular over time

 

Location: face

Pretibial myxedema / thyroid dermopathy

Etiology: 
 

Cause: dermal fibroblasts

 

Description: plaques of thick, scaly skin and swelling 

 

Location: lower legs

 

Associated with: Graves disease (hyperthyroidism); if not at pretibial region = related to hypothyroidism

Primary Cutaneous Anaplastic Large Cell Lymphoma (ALCL)

Etiology: 
 

Cause: t(2;5)(p23;q35) translocation resulting in a fusion gene product of receptor tyrosine kinase ALK with nucleophosmin

 

Description: rapidly-growing single nodule or plaque that typically is red to violaceous, at least 2 cm in diameter, and often ulcerates

 

Location: upper half of the body is most commonly involved

 

At risk: 50+ yo males

Prurigo Nodularis

Etiology: 
 

  • Sx: intensely itchy, firm nodules; can be extremely uncomfortable, impacting sleep and potentially leading to anxiety and depression

  • Tx: JAK-I, ILK

Pseudofolliculitis Barbae / Razor Bumps

Etiology: 
 

Cause: shaving, which lead to ingrown hair

 

Description: firm, hyperpigmented papules and pustules that are painful and pruritic

 

Location: face + neck

 

At risk: Black males

Psoriasis

Etiology: 
 

  • Appearance: well demarcated pink erythematous plaque with silver scale

  • Nail changes: pitting, onycholysis, subungal hyperkeratosis, oil drop sign (yellow-orange discoloration)

  • Tx: 

    • localized: high potency steroid +/- topical vitamin D

    • other options: tazarotene, calcineurin inhibitors, Taltz, Otezla (apremilast)

  • Cause: T cells triggered (stress, skin injury, infection, cold, dry weather, tobacco) to attack skin cells

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  • Description: dry, raised skin patches (plaques) covered with gray or silver scales 

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  • Location: hairline, elbows, knees (extensor surfaces)

Purpura

Etiology: 
Description: 4 - 10 mm in diameter, flat, and red, purple in color

Pustular Psoriasis

Etiology: 
 

  • Sx: presents in 3rd trimester

  • Appearamce: symmetric erythematous plaques with pustules that start in flexural areas and spread centrifugally

  • Location: trunk and extremities

  • Ass sx: fever, malaise, nausea, vomiting, anorexia 

  • Tx: CCS, low dose cyclosporine, infliximab

  • Prog: increased risk to fetus

  • Cause: triggers from infections, stress, corticosteroid treatment withdrawal, and pregnancy

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  • Description: pus-filled blisters on plaques, which are patches of scaly, flaky skin

Pyoderma Gangrenosum

Etiology: 
 

Description: painful, symmetrical necrotic base that progresses over 1 month

 

Location: legs

 

Associated with: IBD

Pyogenic granuloma / Capillary lobular hemangioma

Etiology: 
 

Cause: trauma, hormonal changes, medications, Staph. aureus infection 

 

Description: lesion <2.5cm wide that grows beyond the surface of epithelium (exophytic) with a red to purple surface; bleeds very easily

 

At risk: 20-30 yo females 

 

Associated with: morbid obesity (PG will be very large)

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