Transcript special skin lesions

BASIC STRUCTURE & FUNCTION OF THE
SKIN AND CUTANEOUS SIGNS,
PRINCIPLES OF DERMATOLOGIC
DIAGNOSIS
Oktay Taşkapan, MD
Professor of Dermatology & Allergy, Chair,
Department of Dermatovenereology
Yeditepe University, Faculty of Medicine
İstanbul
BASIC STRUCTURE & FUNCTION OF THE SKIN
AND CUTANEOUS SIGNS
To Sam Shuster, who showed me that
there is more to dermatology than
meets the eye.
J.L.Burton,MD
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Epidermis
Dermis
Subcutis (SC tissue)
Epidermal appendages (adnexa)
• The skin is the largest organ in the body
• It separates the body's internal environment from the
external environment
• A channel of communication with the outside world;
protects the body from water loss; uses specialized
pigment cells, called melanocytes, to protect the
body from ultraviolet radiation; participates in calcium
homeostasis by contributing to the body's supply of
vitamin D; and helps regulate body temperature
and metabolism.
EMBRYOLOGY
• First weeks of life  Periderm
• Third month  Adnexal structures
• Epidermal stem cells  Epidermis, sweat gland
epithelium and hair epithelium
• Epidermis and epidermal appendages (hairs, sebaceous
glands, eccrine glands, apocrine glands and nails):
Ectoderm
• Dermis, SC fat, vessels, muscles: Mesoderm
• Nerves and melanocytes: Neuroectoderm and neural
crest
The skin is composed of diverse cell types of
both ectodermal (e.g. keratinocytes,
melanocytes, Merkel cells, neurons) and
mesodermal (e.g. fibroblasts, hematopoietic
cells such as Langerhans cells, endothelial
cells) lineages.
Epidermis
• The epidermis is formed mainly by keratinocytes
• They synthesize keratin, a filamentous protein that
serves a protective function
• Palms and soles: Epidermis 1.5 mm
• Eyelid: Epidermis 0.1 mm
Keratinocytes
• Keratin, a complex filamentous protein, is the
surface coat of the epidermis, and the structural
component of hair and nails
• Keratins are critical for normal epidermal function
• Basal layer (stratum germinativum), malpighian or
prickle layer (s.spinosum), granular layer
(s.granulosum: Keratohyaline granules), s.lucidum
and horny layer (s.corneum)
• Tonofilaments and desmosomes
• Programmed process of maturation resulting in
death  Terminal differentiation
• The epidermal transit time is about one month
• Keratinocytes play an active role in the immune
function
• They secrete cytokines and inflammatory mediators
• They express ICAM-1 and MHC class II molecules on
their surface
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Keratinocytes
Melanocytes
Langerhans cells
Merkel cells
Diagrammatic cross-section of the skin and panniculus
Melanocytes
• Pigment producing (dendritic) cells of the epidermis /
neural crest origin
• One melanocyte  a great number of keratinocytes
(“epidermal melanin unit”)
• Basal layer at a frequency of approximately 1 in every
10 basal keratinocytes (sun protected trunk epidermis)
• Racial differences in skin colour are caused by the
number, size and distribution of the melanosomes
(pigment granules within keratinocytes)
• Within keratinocytes, melanin forms a photoprotective
cap over the nucleus
• Melanin is formed in melanozomes
• Melanosomes are travelled along dendrites
• Melanosomes are injected into the cytoplasm
of the neighbouring keratinocytes
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Langerhans cells
Found scattered among keratinocytes of the S.spinosum
3-5 % of the cells in this layer
Connected to adjacent keratinocytes by the desmosomes
Birbeck granules
Bone marrow origin
Recognition, uptake, processing and presentation of
antigens to sensitized T lymphocytes [“Antigen
Presenting Cells (APC) in cutaneous immunity]
Merkel Cells
• Located above the basement membrane zone
• Direct connections with adjacent keratinocytes by
desmosomes
• Synaptic contacts with somatosensory afferents
• Sense of light touch discrimination of shapes and
textures (act as receptor for mechanical stimuli).
Dermis
Diagrammatic cross-section of the skin and panniculus
Dermis: Cells, fibers and ground substance
• The constituents of the dermis are mesodermal in
origin except for nerves which derive from the neural
crest
• 0.3 mm on the eyelid, 3.0 mm on the back
• The principal component of the dermis is collagen
(fibrous proteins)
• The fibroblast synthesizes the procollagen molecule,
reticulum fibers, elastic fibers and the ground
substance (extracellular matrix): Connective tissue
• Ground substance: Sulfated acid mucopolysaccharide
(chondroitin sulfate, dermatan sulfate, electrolytes)
• Histiocytes (macrophages), fibroblasts, lymphocytes,
plasma cells, mast cells
• Collagen is the major stress-resistant material of
the skin
• Elastic fibers have a role in maintaining elasticity
• Papillary dermis: The thin upper layer, composed of
thin, haphazardly arranged collagen fibers
• Reticular dermis: The thicker lower layer, extends
from the base of the papillary layer to the SC tissue
and is composed of thick collagen fibers
• Dermal papillae – Rete ridge
Dermoepidermal junction
• DEJ is formed by the “basement membrane zone”
• A structural support holding the epidermis and
dermis together
• It is considered a porous semipermeable filter which
permits exchange of cells and fluid
Epidermal appendages: Adnexa
• Hair follicles, sebaceous glands (pilosebaceous
units), eccrine and apocrine glands, nails
Diagrammatic cross-section of the skin and panniculus
Hair follicles
• Infundibular segment
(from its surface
opening to the
entrance of the
sebaceous duct)
• Isthmus (between the
sebaceous duct and
the insertion of the
arrector pili muscle)
• Hair bulb
• On the scalp, anagen, active growth phase,
lasts about 3-5 years
• 85-90 % of all scalp hairs are in the anagen
phase (0.37 mm / day)
• Catagen (involution phase): 2 weeks
• Telogen (resting phase): 3-5 months
• Each follicle functions as an independent unit
Sebaceous glands
• Greatest abundance on the face and scalp
• Distributed throughout all skin sites except the palms
and soles
• Mostly associated with hair follicles (pilosebaceous unit)
• The main function of the sebaceous glands is to provide
lipids, which lubricate the hair shaft and, along with
lipids produced by the epidermal cells, maintain a lipid
film on the skin surface
Eccrine sweat units
• Most abundant on the palms, soles, forehead,
and axillae
• Cholinergic innervation
• Heat and emotional stress
• Thermoregulation, acid mantle
Diagrammatic cross-section of the skin and panniculus
Apocrine units
• Open into the infundibular portion of the hair
follicle
• Adrenergic innervation
• Apocrine sweat is odorless until it reaches the
skin surface, where it is altered by bacteria
• Generally confined to axillae, areolae,
anogenital region, external auditory canal, and
eyelids
• Its function is unknown
Nails
• Act to assist in grapping
small objects and in
protecting the fingertip
• Matrix keratinization
leads to the formation of
the nail plate
• Fingernails: 0.1 mm/day
Blood vessels, muscles and nerves
Dermal vasculature
• The subpapillary plexus (upper horizontal network)
• Lower horizontal (deep) plexus is found at the
dermal-SC interface and is composed of larger blood
vessels
• Associated with the vascular plexus are dermal
lymphatics and nerves
Diagrammatic cross-section of the skin and panniculus
Muscles
• Smooth muscle (SM): Arrectores pilorum, tunic dartos
of the scrotum, in the areolas around the nipples
• Anogenital skin: Scattered SM throughout the dermis
• The muscularis of dermal and SC blood vessels
• Glomus bodies: Specialized aggregates of SM cells
found between arterioles and venules (prominent on
the digits and at the lateral margins of the palms and
soles)
• Superficial muscular aponeurotic system (SMAS):
Striated muscle of neck and face
Nerves
• The dermis is rich in nerves (neurovascular bundle)
• Touch and pressure are mediated by Meissner
corpuscles found in the dermal papillae (particularly
on the digits, palms and soles) and Vater-Pacini
corpuscles located in the deeper portion of the dermis
of weight bearing surfaces and genitalia
• Temperature, pain and itch sensation are transmitted
by unmyelinated nerve fibers
• Postganglionic adrenergic fibers of ANS:
Vasoconstriction, apocrine gland secretions, and
contraction of arrector pili muscles
• Cholinergic fibers: Eccrine sweat secretion
Subcutaneous tissue
Subcutaneous tissue (Fat)
• SC fat: Lobules of lipocytes / Generous on the
abdomen and buttocks
• Panniculus, lobules of fat cells or lipocytes, is seperated
by fibrous septa composed of collagen and large blood
vessels
• Repository of energy and an endocrine organ
• Hormone conversions (androstenedione into estrone)
• Leptin, a hormone that regulates body weight via the
hypothalamus, is produced in lipocytes
CUTANEOUS SIGNS
SKIN LESIONS
(Elementary lesions)
• Primary skin lesions
• Secondary skin lesions
• Special skin lesions
SKIN LESIONS
PRIMARY SKIN LESIONS
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Macule
Papule
Plaque
Nodule
Tumor
Wheal
Pustule
Blisters: Vesicle
and bulla
SECONDARY SKIN LESIONS
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Scale
Crust
Erosion
Ulcer
Fissure
Atrophy
Scar
SPECIAL SKIN LESIONS
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Excoriation
Comedone
Milia
Cyst
Burrow
Lichenification
Telangiectasia
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Erythema
Petechiae
Purpura
Ecchymosis
Rhagade
Poikiloderma
Sclerosis
Primary skin lesions
Macule
• A flat, circumscribed lesion
which may be brown, blue,
red or hypopigmented
• The lesions larger than 1 cm
in diameter is defined as
“patch”
Papule
• An elevated solid lesion less
than 1.0 cm in diameter
Plaque
• A circumscribed, elevated,
superficial, solid lesion more
than 1.0 cm in diameter which is
often formed by confluence of
papules
Nodule
• A circumscribed, elevated, solid
lesion more than 1.0 cm in
diameter
• A large nodule (usually more
than 2.0 cm in diameter) is
referred to as a “tumor”
Wheal
• A firm, edematous plaque resulting
from infiltration of the dermis with
fluid (“urticaria”, “hive”)
• The resulting edema causes surface
blanching with an inflammatory halo
• Raised, white, compressible,
evanescent and accompanied by a
surrounding red flare
Blisters: Vesicle and bulla
• Vesicle: A circumscribed
collection of free fluid up
to 0.5 cm in diameter
• Bulla: A circumscribed
collection of free fluid
more than 0.5 cm in
diameter
Pustule
• A circumscribed collection of
leukocytes and free fluid
• A blister filled with pus
• Vesicles and bullae may evolve
into pustules
Secondary skin lesions
Scale
• Scales are cornified
epithelial cells often
mixed with serum,
bacteria, extravasated
white or red blood cells
and other debris
• Psoriasiform,
pityriasiform,
ichthyosiform,
exfoliative etc.
Crust
• A collection of dried
serum and cellular
debris; a scab
• Crusts develop as a
pustule dries out or as
an excoriation or ulcer
heals
• Clear, hemorrhagic,
yellow etc.
Erosion
• A focal loss of epidermis
• Erosions don’t penetrate
below the dermoepidermal
junction
• They heal without scarring
• Much wider than it is deep
• Some causes: Maceration,
friction, rupture of a
blister or pustule, 1st or
2nd degree burn
Ulcer
• A focal loss of epidermis and
dermis, or subcutaneous tissue
• They heal with scarring
• Often deeper than it is wide
• Some causes: External damage,
deep infections, pressure etc
Fissure
• A linear loss of epidermis and dermis with
sharply defined, nearly vertical walls
• A deep linear lesion (a deep rhagade)
Atrophy
• A depression or thinning
in the skin resulting from
thinning of the epidermis
or dermis
• Often accompanied by
loss of normal skin
markings
Scar
• An abnormal formation of
connective tissue implying
dermal damage
• After injury, scars are
initially thick and pink, but
with time become white
and atrophic
Special skin lesions
Erythema
• Redness due to increased skin perfusion
• Erythema blanches on pressure
Purpura, petechiae and ecchymosis
• Purpura: Discoloration of
the skin or mucosa due to
extravasation of red cells
• Petechiae: Small purpuric
lesions less than 5 mm in
diameter
• Ecchymosis: A large
extravasation of blood (a
bruise)
• They don’t blanch on
pressure
Rhagade
• Rhagades are superficial linear cracks or tears
radiating from the mouth and nose or, less
frequently, the anus
Telangiectasia
• Permanently dilated, visible small superficial
blood vessels
• Blanch on pressure
Poikiloderma
• Combination of atrophy, hyper-and hypopigmentation
and telangiectases: Chronic radiation damage, UV,
mycosis fungoides etc.
Sclerosis
• Dermal thickening and hardening
Comedone
• A plug of sebaceous and keratinous material lodged in
the opening of a hair follicle; the follicular orifice may
be dilated (blackhead) or narrowed (whitehead or
closed comedone)
Excoriation
• An erosion caused by scratching
Milia
• Small, superficial keratin cyst with no visible
opening
Cyst
• A circumscribed lesion with a wall and a
lumen; the lumen may contain fluid or solid
matter
Burrow
• A narrow, elevated, tortuous channel produced
by a parasite
Lichenification
• An area of thickened epidermis induced by scratching
• The skin lines are accentuated
Basic terminology of dermatopathology
• Epidermal changes: Hyperkeratosis, hypokeratosis,
orthokeratosis, parakeratosis, dyskeratosis,
hypergranulosis, acanthosis, hyperplasia, atrophy,
spongiosis, exocytosis, acantholysis
• Dermal changes: Papillomatosis, actinic elastosis,
changes in collagen and elastin, material deposition,
inflammation, vasculitis
• Subcutaneous changes: Panniculitis (lobular / septal)
Epidermal changes
• Hyperkeratosis: Thickening of the s.corneum
• Parakeratosis: Retention of nuclei in s.corneum,
often combined with a reduced to absent granular
layer
• Hypergranulosis: Thickening of the granular layer
• Acanthosis: Thickening of the growing or midepidermis (s.spinosum) by an increased number of
cell layers
• Spongiosis: Intercellular edema in the epidermis,
usually the result of inflammation
• Acantholysis: Dissolution of the desmosomal
contactsin the epidermis, producing almost round
epidermal cells in blister spaces
Dermal changes
• Papillomatosis: Elongation of the rete ridges and
dermal papillaeand thickening of the papillary dermis
• Actinic elastosis: Eosinophilic collagen acquires a
bluish tint and may form larger clumped fibers
• Changes in collagen and elastin
• Material deposition: Amyloid, hyaline, mucin,
calcium, etc.
• Inflammation: Lymphocytes, neutrophils, eosinophils,
plasma cells, mast cells, dendritic cells and
combinations / perivascular, periappendageal, diffuse
etc.
• Vasculitis: Inflammatory cells in the vessel wall,
necrosis, fibrin deposition and fragments of neutrophils
in the adjacent tissue (vessel wall damage 
erythrocyte extravasation)
BASIC PRINCIPLES
• “It is the patient who seeks treatment, not the rash”,
and good rapport and understanding will never be
achieved without talking to the patient.
• Appearances can be misleading, and serious mistakes
will eventually be made by the dermatologist who
ignores the patient’s previous medical history and
medication.
Patient Evaluation
• A detailed history: History of present illness, family
history, occupation, hobbies, routine household
activities, animal contact, diet, seasonal variation,
past history, association with menses and pregnancy,
medication history, travel, sexual activity
• Physical examination: Patients must be undressed
and fully examined. A total examination should
include the entire skin, hair, nails, mouth, genitalia
and anal region.
• Further investigations: Skin biopsy, patch test,
prick tests, dermatoscopy, scrapings for fungus,
swabs and blister fluid for bacteriology, blood tests
etc.
• When did the trouble start ?
• How does sunlight affect it ?
• Where did it start ?
• What ointments, creams or
lotions have you used ?
• Has it spread ?
• Does it come and go ? If so, do
the spots come in crops ?
• Does it itch ?
• Do you have any contacts with a
similar rash ?
• Any history of previous skin
disease ?
• Does it ever blister ? If so, were • Any history of asthma, or hay
the blisters filled with clear fluid ?
fever ?
• What makes it better ?
• What makes it worse ?
• Any family history of skin
disease, asthma or hay fever ?
• Any previous illnesses ?
• What tablets, medicines or
injections have you had in the
last six months ?
PHYSICAL EXAMINATION
• A good light (preferably daylight)
• A magnifying glass
• A torch
PHYSICAL EXAMINATION
• Describe the lesions
• Note the arrangement of the lesions (closely
grouped, diffusely scattered, linear pattern,
annular pattern etc.)
• Palpate the lesions gently (soft, firm, tender,
hot etc.)
• Note the distribution of the dermatosis
• Note any special / characteristic features
Configuration
Distribution
Arrangement
Shape or configuration of skin lesions
Distribution of multiple lesions
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Dermatomal / zosteriform
Blaschkoid
Lymphangitic
Sun exposed
Sun protected
Acral
Truncal
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Extensor
Flexor
Intertriginous
Localized
Generalized
Bilateral symmetric
Universal
Dermatomal
Blaschkoid
Arrangement of multiple lesions