P
Paget disease
Etiology: DCIS
Description: erythematous, pruritic, ulcerated skin at the nipple and breast
Palmoplantar Verruca
Appearance: thick, endophytic papules
Papillary Hidradenoma / Hidradenoma Papilliferum
Etiology: 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
Appearance: hyperhidrosis + periodontitis with severe gingivitis
Inheritance: AR
Peau d’orange
Etiology: 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
Tx: taper steroids, oral tetracycline, topical metronidazole, erythromycin, tacrolimus
Petechiae
Description: Tiny 1-2 mm, initially purpuric, non-blanchable macules resulting from tiny hemorrhages
Peutz-Jeghers Syndrome (PJS)
Etiology: mutations in serine/threonine kinase 11 (STK11)
Inheritance: AD
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
Define: rare, inherited genetic disorder characterized by patches of skin and hair that lack pigment
Etiology: mutation inactivating c-KIT gene
Inheritance: AD
​Description: white forelock with white patches of skin
Location: face (chin), trunk, + distal extremities
Pigmentary Demarcation Line
Define: abrupt transition between areas of darker and lighter pigmentation
At risk: darker skin tones
Pigmented DFSP (Bednar tumor)
At risk: African American
Pigmented Purpuric Dermatosis (PPD)
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: 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
Define: benign (non-cancerous) skin tumor that arises from hair follicle cells
Appearance: small, hard, and slow-growing lump
teeter toter sign​
Location: head or neck
Histo: ghost cells
Pityriasis Alba
Etiology: 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
Dermatoscope: spores grouped together in hair follicle
POEMS Syndrome
Description: hyperpigmentation, hemangiomas, hypertrichosis, and scleroderma-like skin thickening
Polyarteritis Nodosa (PAN)
Etiology: 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)
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)
Appearance: erythematous papules, vesicles, plaque on sun exposed skin only
Tx: antihistamines (Zyrtec and Benadryl), steroid injection in office
Etiology: stretching of the skin elicits an immune response due to connective tissue damage
​Description: itchy, bumpy rash that starts in the stretch marks of the abdomen
Poroma
Etiology:
Location: plantar surface
​
Porphyria Cutanea Tarda
Etiology: mutation in UROD gene = affecting uroporphyrinogen decarboxylase = accumulates uroporphyrin
Inheritance: AD
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: 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: 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
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: shaving, which lead to ingrown hair
Description: firm, hyperpigmented papules and pustules that are painful and pruritic
Location: face + neck
At risk: African American males
Psoriasis
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
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other options: tazarotene, calcineurin inhibitors, Taltz, Otezla (apremilast), Skyrizi, Tremfya
Etiology: 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
Description: 4 - 10 mm in diameter, flat, and red, purple in color
Pustular Psoriasis
Sx: presents in 3rd trimester
Appearance: 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
Etiology: triggers from infections, stress, corticosteroid treatment withdrawal, and pregnancy
​Description: pus-filled blisters on plaques, which are patches of scaly, flaky skin
Pyoderma Gangrenosum
Description: painful, symmetrical necrotic base that progresses over 1 month
Location: legs
Associated with: IBD