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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 / Herpes Gestationis

Etiology: IgG autoantibodies that target BP180

Appearance: erythematous papules or plaque around the umbilicus + then spreads to most areas of body, but sparing face + mucous membranes; 2-4 weeks later large, tense bullae form

Sx: intensely itchy

Tx: high potency topical CS, but many end up requiring oral CS

Risk to fetus = prematurity

Pemphigus Foliaceus

Etiology: IgG autoantibodies to desmoglein 1
At risk: Tunisia
Appearance: flaccid, superficial bullae that rupture easily 
Location: seb derm distribution (NO oral lesions)
Tx: systemic CS

Pemphigus Vegetans

Locations: Intertriginous

Pemphigus Vulgaris

Etiology: IgG autoantibodies to desmoglein-1 and/or desmoglein-3; can be triggered by meds (#1 captopril + penicillamine)
Location: mucosal membrane + skin
Appearance: flaccid bullae that easily rupture (+ Nikolsky sign; + Asboe-Hansen sign)
Sx: extremely painful
At risk: middle aged to young adults; Ashkenazi Jews
Tx: systemic CS

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

  •  

  • Description: white forelock with white patches of skin 

  •  

  • 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 Lichenoids Et Varioliformis (PLEVA)

Etiology:

Pityriasis Rosea

Etiology: not clear; some suggest HHV-6 or 7

At risk: older children + young adults

Appearance: begins with a single "herald patch" or "mother patch" which is a salmon colored oval plaque, usually on neck, back or chest. Patch becomes scaly and develops central clearing, forming "collarettes of scale." Then numerous similar but smaller patches. appear on trunk + extremities following skin tension lines (Christmas tree distribution).

Tx: only topical CS to relieve pruritus

Pityriasis (Tinea) Versicolor

Etiology: Malassezia furfur or Malassezia globosa

Appearance: hyper or hypo pigmented or salmon colored scaly patches

Location: sebum rich areas 

Tx: selenium sulfide, ketoconazole shampoo, topical or oral azoles

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: vascular malformation of capillaries and post capillary venules in dermis
Appearance: pink, red, or violaceous sharply demarcated patches that darken + thicken overtime
Location: face, unilateral
Tx: PDL
Prog: persist throughout life + grow proportionally with child

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

Proteus syndrome

Etiology: mosaic non inherited mutation in AKT1 gene

Appearance: port wine stains

Location: limbs, digit, skull

Prog: at risk for developing DVTs, PEs

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

  •  

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

  •  

  • 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

  •  

  • 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: mutation in BRAF plays a key role; medications (retinoids, TK inhibitors), trauma, laser therapy

At risk: 20-30 yo

Appearance: small red papule that grows over several weeks into a nodule

Location: hands, lower lip, gingiva

Tx: full thickness excision or shave excision for pedunculated lesions

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