An Introduction To Dermatology

Laila Nour

Dermatology…..what is it?• Dermatology is defined in the New Oxford Dictionary

of English as ‘The branch of medicine concerned with the diagnosis and treatment of Skin disorders.’

• Internal medicine• Environmental Factors• Psychiatry Rook’s Textbook of Dermatology 8th edition

Anatomy & Histology• Epidermis• Epidermal Derivatives (Hairs, Nails, Sebaceous

& Sweat Galnds)• Dermis• Panniculus Adiposus (Hypodermis)

Anatomy & Histology

Epidermis4 types of cells:

• Keratinocytes• Melanocytes• Langerhans Cells• Melanocytes

Epidermis

Keratinocytes• 80-95% of Epidermal Cells• Keratinization• 4 Main Layers: Basal Spinous Granular Stratum Corneum

Keratinocytes

Keratinocytes

Keratinocytes

Keratin• intermediate filaments • hallmark of all epithelial cells• 54 Keratin Genes : 34-epithelial keratins , 17-

hair keratins• Fillagrin i.e: Keratohyaline

Melanocytes

• neural crest-derived• pigment-synthesizing dendritic

cells • m/k : 1/10• I m 36 keratinocytes• reside primarily in the basal

layer

Melanocytes

Melanocytes

Melanocytes

Langerhans Cells• 2-8% of total count of cells• dendritic antigen-processing

and -presenting cells• Phagocytosis• Interactions with

Lymphocytes• dSEARCH

Langerhans Cells

Langerhans Cells

Merkel Cells• 0.2 – 5% of total cells• induction or stimulation of perifollicular or dermal

nerve plexuses via a direct complex• stimulation of keratinocyte proliferation and

maintenance of their differentiation• histogenesis of the nail• release of various bioactive substances to the dermis.

Merkel Cells• cyclical changes in the number of dendritic-

type Merkel cells in rat skin suggest a secretory function related to the hair cycle *

Merkel cell-derived neoplasms are particularly aggressive and difficult to treat

*.Nakafusa J, Narisawa Y, Shinogi T, et al. Changes in the number of Merkel cells with the hair cycle in hair discs on rat back skin. Br J Dermatol. Nov 2006;155(5):883-9. [Medline].

Merkel Cell Carcinoma

Dermal-Epidermal Junction• three supramolecular networks: hemidesmosome-anchoring filament complex basement membrane itself anchoring fibrils

Dermal-Epidermal Junction

Dermal-Epidermal Junction

Dermis• papillary layer• reticular layer• composed of three

types of connective tissue: collagen, elastic tissue, and reticular fibers

Dermis

Dermis

Panniculus Adiposus(Hypodermis)

Functions of The Skin• Protection• Sensation• Thermoregulation• Circulation• Metabolic• Movement• Secretion & absorption

Dermatology Alphabet!

Macule• Change in color• Well determined• No palpable change in

structure

Patch• A macule that is larger than

0.5 cm

Papule• An elevated solid lesion up to 0.5 cm

in diameter

• Bigger Plaques

Nodule• A circumscribed, elevated, solid lesion more

than 0.5 cm in diameter

• Bigger Tumor/mass OR plaques

Vesicle• A circumscribed collection of free fluid

up to 0.5 cm in diameter

• Bigger Bulla

Wheal• A firm edematous plaque resulting

from infiltration of the dermis with fluid; wheals are transient and may last only a few hours

Pustule• A circumscribed collection of

leukocytes and free fluid that varies in size

Scales• Excess dead epidermal cells that are

produced by abnormal keratinization and shedding

Erosion• A focal loss of epidermis• do not penetrate below the dej and

therefore heal without scarring

Ulcer• A focal loss of epidermis & dermis• heal with scarring

Dermatologic Story & Examination

• Initial clinical impression: Does the patient appear ill?

• Physical examination: detailed examination of the skin, hair, nails, and mucous membranes

• Four cardinal features1- Type of lesion

• Four cardinal features2- Shape of individual lesions

• Four cardinal features• Arrangement of multiple lesions

• Four cardinal featuresDistribution • Extent of involvement• Pattern

• Characteristic locations• Three major characteristics

• Color diascopy wood• Consistency and feel of lesion• Anatomic components of the

skin primarily affected

• General physical examination as indicated by the clinical presentation• Review of systems as indicated by clinical situation• Review of systems for growths suspicious for, or associated with,

malignancy

• Medication history• Past medical history• Social history

Thanks!