Dermatitis= eczema. it is a heterogeneous group of disorders with similar appearance and histopathologic findings but different etiologies. The location of the dermatitis provides clues to the underlying etiology. clinical features of all dermatitis include : poorly demarcated plaques ( biggest clue to differentiate from papulosquamous disorders), erythema, vesiculaiton/papulaiton, linear erosions from excoriation due to pruritus, lichenificatio, fissuring and scale


acute dermatitis: erythema, vesicles and bull lesions as


chronic dermatitis: may be red, scaly, xerotic and lichenified with fissuring

atopic

contact

irritant (ICD)


non-immunologic response to chemicals or physical agents that disrupt normal epidermal barrier. common causes include stops, cleaners, acids and alkalis or frequent hand washing with soap. hands are the most common site. mild ICD presents with a glazed appearance. if due to a strong irritant it may present with pain , erythema, swelling or blistering.

allergic (ACD)


cell mediated, delayed type 4 hypersensitivity reaction from contact with specific allergen. it requires prior sensitization, which can occur with few exposures or years of an exposure. most common allergins: urushiol in toxicodendron family plants ( poison ivy, oak, and sumac), metals (nickel, cobalt, chromate), fragrances, preservatives, topical antibiotics


pathogenesis:
-step1: sensitization- takes 7-21 days . antigen penetrates epidermis and binds protein, it is then recognized by antigen presenting cells . the APC carries the antigen to lymph node for naive T-cell presentation
-step 2: memory- t-cell expansion (cloning) occurs, increased CCL27 expression
-step3: challenge- skin re-exposed to allergic chemical, allergic "recognition" occurs 8-120 h post re-exposure, recruitment of memory T-cells and secretion of cytokines.


-step4: inflammation- vasodilation and leukocyte recruitment--> dermatitis at site of contact and prior exporue
-step 5: resolution- macrophages remove allergen, loose of antigen stimulation


diagnosis: exposure to high risk allergein, physical exam maybe be well demarcated and linear, patch testing for delayed 4 allergies only

stasis


occurs in legs and dependent region. it is typically bilateral. it is due to chronic swelling and edema.


acute: red, edematous tender and it mimics cellulitis.


chronic: red, fissured, scaly papular lichenified.

nummular
more common in older individuals, and is associated with dry skin. presents with round, light pink, scaly, thin 1-3 cm plaques on extremities/trunk. It is more well demarcated than other types of dermatitis so it is often confused with papulosquamous condition.


pathogenesis: unknown but may be linked to impaired skin barrier function

lichen simplex chronicus/prurigo nodular


chronic, intensely pruritic skin condition triggered by repeated rubbing and scratching of the skin. typically presents with a solitary well-defined pink to tan, thick and lichenified plaque. Commonly on the lateral neck , scrotum/vulva, and dorsal foot

seborrheic


very common disorder associated with sebum production and malassezia yeast.


infants: present with cradle cap, pink to yellow macule and patches with white greasy scales on the scalp, face and diaper area.


adults: present with pink plaques with white greasy scales on the scalp, forehead, eyebrows , eyelash line , nasolabial folds, ears, upper chest and interiginous areas

20% of children in developed countries. often occurs before the age 5. typically clears by adolescence. only 1-3% of adults affected. patients will often have a personal or family hisotry of atopy (edema, asthma or allergic rhinitis)


pathogenesis: Genetics- skin barrier dysfunction from a filaggrin mutation. impaired immune response- activation of TH2 immune response, frequency staph infections (impetigo), environmental factors - decreed infectious agents and antigenic pollutants may play are role in development, high altitude, low temperatures, low humidity.


in infants: acute/weeping/crusting dermatitis. distribution is usally on face, cheeks, forehead, scalp, extensor extremities, and tends to spare the diaper area


in childhood: less oozing, more lichenificaiton, distribution is more localized in the flexure areas: neck wrists ankles, anticupital and popliteal fossa, hands and feet, if facial involvement it is more periocular/perioral


in teens/adults: lechenification predominates, prurigo nodular may be a manifestation. distribution is flexural . severity decreases with age and may become more localized with isolated insolvent of hands, eyelids, nipples.


associated conditions: xerosis, hyper linear palms, keratosis pillars, pityriasis alba, intolerance to wools

Dyshidrotic Dermatitis (pompholyx)


unknown cause. presents with grouped 2-5 mm vesicles, sometimes likened to "tapioca pudding" commonly occurs on the lateral fingers, central palms, insteps and lateral borders of the feet.

Melanocytic neoplasms

Benign

Freckles (ephelides)


hyper pigmented tan macules uslally found in sun-exposed areas. increased melanin in epidermis but NOT increased number in melanocytes. very common in caucasians after age 3 especially in fair skinned, red-haired individuals. common in face, arms, upper back

Cafe au lait macule


tan pigmented patch present since birth. increased melanin in epidermis but NOT increased number of melanocytes. associated with neurofibromatosis if 6 or more present.

Lentigo


light tan- brown macules. increased number of melanocytes.


lentigo simplex: may be congenital or may arise in childhood


solar (actinic) lentigo- liver spots: commonly seen in older adults on sun exposed areas.

Acquired melaocytic nevus ( mole)


more common in caucasians with onset in early childhood. can get new lesions until age 40. benign nevi are < 1 cm and have uniform colors/borders


junctional nevus: macular pink to black macules, cells confined to the base of the epidermis


compound nevus: slightly raised and pigmented cells in epidermis and dermis


dermal nevus: papular with or without pigment, cells in Demis only.

Congenital melanocytes nevus


1% of Caucasian infants. brown or black plaque or nodule. often several centimeters in diameter or may sober a whole body region. usally grows hair. categorized by size. large and giant CMN at very high risk for developing melanoma within it

Metastatic

melanoma


incidence is on the rise with a lifetime risk higher in males than females. most common locations are on the trunk, especially the upper back extremities and face. accurate stating requires measurement of the breslow depth (distance between the gradual layer of the epidermis to the deepest portion of the melanoma in mm) thin m melanomas with a breslow thickness of >4 mm have a poorer survival rate


for melanomas > 0.75-1mm breslow depth we do a sentinel lymph node biopsy which is used for staging Gand prognosis.


pathogenesis: Activated protein kinase (MAPK) pathway:

  • 40-60% of melanomas have an activating mutation in BRAF (V600E)
    -vemurafenib can be used as a BRAF inhibitor in treatment
    -some patients with numerous atypical nevi have a mutation in the CDKN2A gene, which is high risk for melanoma

ABCDE rule : Assymetry, Borders irregular, Color variation, Diameter > 6 mm,Evolution over time



SUperficail Spreading melanoma: 70% of all melanomas, radial growth, affects epidermis only and is not invassive


Lentigo maligna melanoma: 10-30% of all melanomas, presents as large flat lesions on chronically sun-exposed areas, especially head and neck.


nodular melanoma: 10-15% of all melanomas. absent radial growth phase, maybe deep with poor prognosis at time of diagnosis. dark brown to black papule, amelontic variant may be red or pink with non-specific clinical features


aural lentiginous melanoma: 5% melanomas. most common presentation of melanoma in asian and black patients. typically occurs on palms and soles.


risk factors: atypical nevi, congenital nevus, history of mealnoma, FH of melanoma, immunosuppression

Actinic Keratosis, non melanoma skin cancers and Merkel cell carcinoma

Epidermal

Nerve-related

malignant

premalignant

excessive UV exposures is a major cause of AKs, SCC, and BCC


pathogenesis: errors in excision repair lead to mutations --> pyrimadien dimers in DNA

Actinic Keratosis


common precancerous lesion of keratinocytes. typically seen in elderly caucasians on chronically sun exposed areas. presents as solitary/multiple rough papules/plaques. 10% of untreated AKs may because SCC.

Squamous cell carcinoma


second most common skin cancer. some potential for local/distant metastasis. risk factors include UV light, solid organ transplantation, and chronic inflammation. commonly found in sun-exposed regions



SSC in situ (Bowen's disease): limited to epidermis w/no dermal invasions. typically presents as a well-demarcated, rough erythematous, keratitis papule or plaque which is more indurated or tender than an actinic keratosis. when present on nonracial areas it can be misdiagnoses as a rash



bowenoid papulosis: presens as marron to brown verrucous papules on the genitals . etiology: HPV16. low risk of invasive SCC



erythroplasia of Queyrat: etiology-HPV16. presents as a moist, red, eroded, well-circumscribed plaque on gas penis, coral sulcus or foreskin of uncircumcised men. High risk for invasive SCC



Invasive SCC: extends into the dermis. presents as a hyperkeratotic pink plaque or nodule



keratoacanthoma: an invasive SCC variant. presents as a cupped nodule with a central hyperkeratotic core. rapid growth, typically with resolution over 4-6 months. rare reports of metastasis, usually treated as invasive SCC and excise.

Basal cell carcinoma


most common skin cancer usually found in elderly caucasians. rarely metastatic, nodular is most common subtype, presents as translucent pearly papule with erythema, telangiectasia and rolled border; usually on head and neck


pathogenesis: errors in nucleotide excision repair or hereditary mutations affecting hedgehog signaling pathway especially PATCH1 gene



superficial BCC: have a rash like appearance, but look more shiney


sclerotic BCC: most aggressive have scar-like appearance


nodular BCC: may be pigmented mimicking a melanoma

Merkel Cell Carcinoma


rare primary cutaneous neoplasm composed of neuroendocrine cells. highly aggressive with high mortality rate. most common on head/neck of elderly patients. presents as solitary, non-specific , quickly growing shiny pink papule or nodule. highly associated with the Merkel cell polymavirus. immunosuppression is an important risk factor .


treatment: surgery +SNLB. radiation and chemo may be considered for locally aggressive and or metastatic lesions.

Mohs Surgery is the most effective treatment for non-melanoma skin cancers. Dermatologist act as surgeon and pathologist to map out tumor and achieve a tumor free-margin and smaller defect passive. it is used for lesions on head, neck , genitals and fingers. where is a high risk of recurrence.

Benign skin neoplasms these are commonly seen and can be diagnosed clinically.

epidermal

dermal

subcutaneous

hair-follicle

cyts

epidermal cyst


often called 'sebaceous cyst' which is a misnomer. arise from infundibular region of the hair follicle, they are firm, skin colored cyst with a central puncture. keratin within the cyst ha a cheesy consistency. pilar cysts have similar appearance but occur in the scalp and arise from the isthmus region of the hair follicle.

milia


1-2 mm white papules usally found around the eyes and upper face. arise from the infundibular region of hair follicle similar to epidermal cysts.

sebaceous gland

sebaceous gland hyperplasia


2-4mm yellow to skin colored papule often with a central depression. usually found on forehead or central face.

nerve related

neurofibroma

gloms tumor


skin colored to bluish hard nodule tender to touch and painful in response to cold. typically located under the fingernail at the nailed.


Histology: composed of gloms bodies.


glomus bodies are thermoregulatory modified perivascular smooth muscle cells.

fibrohistocytic

Dermatofibroma


firm 3-10 mm papule usally hyperpgmented, often with a slightly hypo pigmented center. most common on extremities, dimple sign may be present

acrochordon (skin tag)


common in people after age 45. skin colored papule with a thin stalk. typically located on neck, axillae and groin

vascular

acquired

cherry hemangioma


small bright red or purple papule commonly seen in females after age 30 on the trunk. common in pregnant women and young children

pyogenic granuloma


common in children and young adults. typically occur asa response to trauma. readily growing exophytic papule which bleeds easily. commonly seen on face, neck ,and distal extremities.

adipose tissue

lipoma


nodule with rubbery consistency. benign neoplasm of mature fat cells may be single or multiple. can occur in any body area

seborrheic keratoses


pressent in up to 50% of adults. tan to brown well demarcated papule/plaque. waxy stuck on appearance with a cerebriform architecture and a hyperkeratotic surface. typically found on the trunk

dermatosis papulosa nigra