PATHOLOGY OF THE SKIN
1. Disorders of pigmentation and melanocytes
 Vitiligo
-a common disorder characterized by partial or complete loss of pigmentproducing melanocytes in the skin- irregular, well-demarcated plaque devoid of
pigmentation
-pathogenetically- autoimmune mechanisms- circulating autoantibodies
against melanocytes, moreover vitiligo may be associated with other disorders
involving autoimmune mechanisms, such as pernicious anemia, Addison disease,
autoimmune thyroiditis
-histologically-loss of melanocytes
Benign pigmented lesions.
melanocytic proliferations are composed of one or more of three types of
cells: melanocytes epidermal, dermal, nevus cells and melanoma cells
-melanocytes are solitary dendritic cells that are generally separated one
from another by other cells, such as keratinocytes or fibroblasts- in contrast
nevus cells proliferate to form solid nests, melanoma cells- have nuclear
abnormalities
 benign pigmented lesions composed of epidermal melanocytes- include
freckles, solar lentigo, melanotic macules in Albright syndrome, and Becker´s
melanosis
 benign pigmented lesions derived from dermal melanocytes include mongolial
spot, the nevi of Ota and Ito, and blue nevus
 benign tumors of nevus cells are called melanocytic nevi- they can be divided
into- junctional, compound, intradermal, and there are special variants of
melanocytic nevi, such as Spitz nevus, congenital melanocytic nevus, and
dysplastic nevus
Lesions of epidermal melanocytes:
 Freckle
-a common pigmented lesion of childhood, tan-red to brown, occurring after
sun exposure, they are small, flat, sun exposure deepens the pigmentation of
freckles (in contrast to lentigo simplex)
histologically- normal number of melanocytes but increased melanin within
basal keratinocytes
 Lentigo
-common benign hyperpigmented macules in the skin, most often in infancy
and childhood, in contrast to freckles they do not darken after sun exposure
-histologically-linear basal hyperpigmentation due to melanocyte hyperplasia
-the term “lentigo” is derived from the Latin “lenz” meaning lens or lentilthus the term refers to small ovoid or lens-shaped pigmented lesions- then the
term has become to be applied to larger pigmented lesions with lentiginous
pattern- which includes basal proliferation of melanocytes arranged as single
cells rather than nests associated with elongation of rete ridges
-two major types of benign lentigo can be distinguished, solar (actinic)
lentigo and lentigo simplex (simple lentigo)
 solar lentigo- occur as multiple lesions in areas exposed to sun, such as
face, extensor surfaces of the forearms, and hands, they occur in the
fifth decade and later
 lentigo simplex- is macular hyperpigmentation that arises in childhood,
these are few scattered lesions without predilection to sun-exposed
skin, they are small symmetrical, few milimeters in diameter
 melanocytic macules of Albright syndrome- Albright syndrome is
characterized by unilateral polyostotic fibrous dysplasia, precocious puberty
and melanotic patches- large in size, few in number, located on the same side
as bone lesions-hyperpigmentation of basal layer
 Becker´s melanosis- occurs most commonly as large patch showing
hyperpigmantation and hypertrichosis on the shoulder, back or chest of a man,
skin lesion is sharply demarcated, histologically- epidermis shows acanthosis,
rete ridges are elongated, basal layer is hyperpigmented, number of
melanocytes is increased
Lesions of dermal melanocytes:
 Mongolian spot- occurs in sacrococcygeal region as a uniformly blue
discoloration, it is present at birth, usually disappears spontaneously within 34 years
histology-the dermis shows in its lower part elongated slender dendritic
cells containing melanin pigment, these cells are scattered between collagen
fibres
 Nevi of Ota and Ito- are dermal melanocyte hamartomas, characterized by
irregular brown-blue discoloration of the skin, there is greater concentration
of dermal melanocytes in upper rather than in lower dermis
 The nevus of Ota- unilateral discoloration of the face composed of blue
and brown, confluent lesions- periorbital, forehead, and nose are involved, blue
discoloration may affect retina, conjuctiva and cornea, the nevus of Ota may be
present at birth
 The nevus of Ito- supraclavicular, scapular and deltoid region is
affected- mottled macular appearance
 Blue nevus- characterized by presence of pigmented spindle dendritic
melanocytes in the reticular dermis associated with alteration in the dermal
collagen architecture
clinically- small well circumscribed, dome-shaped nodule of blue or blueblack colour, the lesion rarely exceeds 1 cm in diameter, most frequently found
on the dorsa of the hands and feet
histologically-melanocytes are elongated, lie grouped in irregular bundles in
the dermis predominantly with their long axes parallel to the epidermis, most
are heavily pigmented with melanin, melanophages are frequently observed near
the bundles of melanocytes, the number of fibroblasts is increased within the
lesion
Benign pigmented lesion composed of nevus cells-melanocytic nevi:
 Nevocellular nevus
-nevus-denotes any congenital skin lesion, nevocellular nevus-refers to a
group of congenital or acquired melanocyte lesions having different histologic
characteristics, but composed of nevus cells mostly in nesting patterns
-clinically- tan-brown papules, five clinical types can be distinguished, flat
lesions, slightly elevated, papillomatous, dome-shaped, and pedunculated lesions
-the first three types are always pigmented, the latter two may or may not
be pigmented
-nevi begin as well-defined nests along the dermoepidermal junctionjuntional nevi, with time- extensions of melanocytes form nest within both
dermis and epidermis- compound nevi
-later epidermal component is lost- intradermal nevi, all these variants are
benign
junctional nevus- nevus cells lie in well-circumscribed nests within the lower
part of epidermis or at the junction with dropping off into the dermis, the nevus
cells are regular, cuboidal or spindle shaped, mostly appear in children
compound nevus- possesses features of both junctional and intradermal
nevi, nevus cell nests are in the epidermis and dermis, and dropping off from the
epidermis, the decrease in size observed in nevi is called maturation- is regarded
as evidence of benignity
intradermal nevus- shows essentially no junctional activity, the upper
dermis contains nests and cords of nevus cells, some intradermal nevi contain
large fat cells, foreign-body giant cells, foci of ossification, and inflammatory
reaction
Special types of melanocytic nevi:
 Spitz nevus- named after Sophie Spitz, who first described it in 1948, also
known as juvenile benign melanoma, or spindle and epithelioid cell nevus
-lesion occurs mostly in children, is solitary, mostly on the lower extremity
and face, it consists of dome-shaped pink nodule, most Spitz nevi are small, less
than 6 mm in diameter
-histologically- the colour is pink because of a scarcity of melanin, (clinically
often looks like hemangioma), nuclei of nevus cells are large slightly polymorphic,
nevus cells are spindle-shaped and epithelioid- picture resembles nodular
melanoma, the epidermis is often hyperplastic (pseudoepitheliomatous
hyperplasia)
-in some examples of Spitz nevus- diffuse fibrosis, these are usually
composed of spindle cells, called desmoplastic Spitz nevus
 Pigmented spindle cell nevus- Nevus of Reed- first described as variant of
Spitz nevus in 1973, the lesion are usually 3-6 mm in diameter, most patients
are young, macro- black flat plaque
-heavy pigmentation and sudden appearance- result in clinical diagnosis of
melanoma
-histologically- pigmented spindle cells of uniform size, heavily pigmented
at the dermal-epidermal junction, nests of spindle melanocytes tend to blend
with keratinocytes
 Congenital melanocytic nevus- is a lesion present at birth, found in 1-2% of
newborn infants, in many instance congenital nevi are larger than acquired
nevi, nevi more than 20 cm in diameter- are called giant congenital nevideeply pigmented and covered by hairs
 Dysplastic nevus- multiple lesions occurring in patients with some melanomas
in family, in relatives, dysplastic nevi may be also solitary without relationship
to melanoma
-criteria for diagnosis of dysplastic nevus include: melanocytic dysplasia,
elongation of rete ridges, lentiginous proliferation of nevus cell in the epidermis,
spindle shape of nevus cells, inflammatory infiltrate mild to moderate
-significance- patients with dysplastic nevi may develop melanoma, but
mostly de novo, and not from pre-existing dysplastic nevus
 Halo nevus- also known as Sutton nevus, represents a pigmented nevus
surrounded by a depigmented zone, halo,
-halo nevus is characterized by heavy lymphocytic infiltrate within and
below the nevus, most persons are children and young adults, and the back is the
most common site
 Malignant melanoma
may be located in situ or may be invasive, invasive melanomas are
characterized by two growth patterns: tumorigenic (vertical growth phase) and
nontumorigenic (radial growth phase)
-melanomas in situ and those with radial growth phase can be divided into:
lentigo maligna, superficial spreading, acral lentiginous, and mucosal lentiginous
types
-invasive melanomas may either arise in association with these in situ types
or de novo- nodular melanoma
-relatively common malignant neoplasm, currently increasing in incidence
-sun exposure seems to be important pathogenetic factor, lightly
pigmented persons are in higher risk
Classification of melanoma
-there are two major categories of melanoma-in the nontumorigenic growth
phase- neoplastic melanocytes are confined to epidermis- melanoma in situ or to
the epidermis and papillary dermis without formation of a tumor massmicroinvasive melanoma - this is called clinically radial growth phase, and
histologically horizontal growth pattern- during this time melanoma does not
metastasize
-this phase is followed by vertical growth phase - characterized by dermal
invasion with tumor formation- means development of capacity to metastasize
Nontumorigenic melanoma- radial growth phase include
 Superficial spreading melanoma- is the most frequent form of melanoma
(about 70% of all cases) most frequent sites are upper back, and lower legs
the lesions are slightly elevated, with palpable borders, and irregular outlines,
often variation in colour, that include tan, brown, blue, gray and pink, the
diameter is less than 6 mm
histologically- the lesion is assymetric, the epidermis is thickened, large
melanocytes are scattered in pagetoid pattern within epidermis, the melanoma
cells lie in nest in lower epidermis
 Lentigo maligna melanoma- morbus Dubreuilh-accounts for about 10% of all
cases of melanoma, typically occurs in chronically sun exposed surfaces of the
elderly- face, back (men), lower legs (women), forearms, the lesion grows
slowly over years, starting as unevenly pigmented macule and gradually
extends the size to several centimeters in diameter, the colour varies from
brown, to black, in contrast to SSM, LMM is not accurately deliniated
histologically- in early stage lentigo maligna shows hyperpigmentation in
periphery with melanocytic proliferation, the epidermis is flattened, some
nesting of melanocytes is observed in junction, the other melanocytes retain
dendritic processes
 Acral lentiginous melanoma- occurs on the hairless skin of palms and soles, and
in the ungual regions, clinically- shows uneven pigmentation with irregular
indefinite borders
histologically-majority of melanocytes are single in lentiginous pattern
located at the junction
Tumorigenic melanoma- vertical growth phase
-any of nontumorigenic types of melanomas may develop vertical growth
phase
 Nodular melanoma- in contrast to other types, contains only vertical growth,
occurs in slightly older patients than the common superficial spreading
melanoma, and is relatively more frequent in men
-nodular melanoma- is elevated variably pigmented papule that increases its
size rapidly, histologically- there is continuous growth of uniformly atypical
melanocytes in dermis, upward pagetoid growth of tumor cells into the epidermis
is typical feature, the tumor cells show great variation in size and shape, often
they are epithelioid and spindle shaped
Variants of melanoma include desmoplastic and neurotropic melanoma
 Desmoplastic melanoma- melanoma cells are elongated and usually amelanotic
and are embedded in markedly fibrotic stroma
 Neurotropic melanoma- is composed of fascicles of spindle shaped melanomas
cells often with desmoplasia, that invade the nerves
Prognosis and management of melanomas
-tumor thickness (described by Breslow) and level of invasion (according to
Clark) are considered to be most important prognostic factors
-level I- (100% 10-year disease-free survival)- melanoma cells confined to
the epidermis-melanoma in situ
-level II (96% survival) - there is extension to the papillary dermismicroinvasive melanoma
-level III (86%)- there is extension of tumor cells throughout the
papillary dermis
-level IV (66%)- are invasive and tumorigenic, invade reticular dermis
-level V (53%)- invade subcutaneous fat
-other prognostic factors, such as mitotic rate, ulceration, histological type,
biological markers are of limited value
treatment: local excision is recommended, with safe margins at least 5 mm
beyond the perimeter of the lesion, clinically positive lymph nodes should be
biopsied
BENIGN EPITHELIAL TUMORS.
 Seborrheic keratosis
-most often in middle-aged and older persons
-uniform tan-brown round granular plaques, histologically exophytic lesions
with hyperplasia of variably pigmented basaloid cells and hyperkeratosis.
 Keratoacanthoma
-common lesion presenting as rapidly growing tumor, typically located in
sun-exposed skin, this is a self-limited lesion that may heal spontaneously
-macroscopically- flesh-colored, superficial lesion several centimeters in
diameter, located on face and hands
histologically- cup-shaped epithelial proliferation enclosing the central
keratin-filled plug, the pattern of keratinization is similar to that one of hair
follicles- no granular cell layer
-minimal inflammation is present within the dermis
Premalignant and malignant epidermal tumors.
 Actinic keratosis- a premalignant dysplastic lesion associated with chronic sun
exposure, macroscopically- usually less than 1 cm in diameter, tan-brown or
red with rough consistency
histologically-there is cytologic atypia in the lower epidermis, frequently
with basal cell hyperplasia and hyperkeratosis, dyskeratosis and parakeratosis
may be present, basal membrane is intact, upper dermis contains inflammatory
infiltrate, local excision is recommended- may undergo malignant transformation
 Squamous cell carcinoma-the most common tumor of sun-exposed skin of
older individuals, sunlight (especially ultraviolet irradiation) is well known
predisposing factor- it causes direct DNA damage in keratinocytes
-in situ squamous cell carcinoma- Bowen disease- appears as welldemarcated red scaling plaque, histologically - full thickness severe dysplastic
changes within the epidermis, basement membrane is intact
-invasive lesions- tend to be ulcerated, histologically invasive tumors vary
from well differentiated with prominent keratinization to highly anaplastic
tumors with abortive keratinization
 Basal cell carcinoma- is common slowly growing tumor in sun-exposed skin, it
grows in locally aggressive manner but does not metastasize, grossly- it
appears as pearly papules or plaques and advanced lesions become ulcerated,
some are melanin pigmented, histologically- basal cell proliferation extending
to the dermis
 Merkel cell carcinoma- a rare malignant neoplasm derived of neuroendocrine
Merkel cells, the tumor is composed of small round basophilic malignant cells
(the cells contain neurosecretory granules) and resemble small cell carcinoma
of the lung
ADNEXAL TUMORS.
-most are single or multiple nondescript nodules, most are benign
 cylindroma- typically occurs as multiple coalescing nodules on the forehead
and scalp, they may be inherited and appear early in life
histologically- they display apocrine differentiation with islands of basaloid
cells within the hyalinized matrix
 syringoma-usually occur as multiple small, tan papules near the lower eyelids,
microscopically- it is composed of tadpole-shaped islands of basaloid
epithelium with focal eccrine differentiation
 trichoepithelioma- may be inherited, usually present as multiple
semitransparent papules on the face, scalp and neck, histologically -composed
of proliferations of basaloid cells forming follicle-like structures
 trichilemmoma- composed of the cells resembling hair follicle infundibulum
TUMORS OF DERMIS.
 Benign fibrous histiocytoma- a heterogenous group of benign neoplasms
composed of dermal fibroblasts and histiocytes, usually in adults, frequently
on legs of young to middle-aged women
grossly- tan-brown firm papules, sometimes tender, histologically-the most
common form is composed of spindle-shaped fibroblasts and histiocytes
(sometimes foamy cells, deposits of hemosiderin)
 Dematofibrosarcoma protuberans- well-differentiated slow-growing tumor of
the skin that is locally aggressive but does not metastasize
grossly- firm solid nodules, plaques, sometime ulcerated- often on the
trunk, histologically- cellular neoplasms composed of radially oriented
fibroblasts in storiform pattern
clinical behavior is that of low grade sarcoma
 Xanthoma- not true neoplasm, but rather focal accumulations of foamy
histiocytes, may be idiopathic, or associated with familiar hyperlipidemia
 Xanthelesma- soft yellow plaques on the eyelids in patients with or without
lipid metabolism abnormalities
 Eruptive xanthoma- sudden occurrence of yellow papules that appear and
disappear with changing plasma lipid levels- located in buttocks, posterior
thighs, knees, etc.
 Tuberous xanthoma- yellow, flat nodules over the joints, especially knees and
elbows
 Tendinous xanthoma- yellow nodules over the Achilles tendon and finger
extensor tendons
All these xanthomas are characterized by variably cellular dermal
aggregates of macrophages with foamy cytoplasm containing cholesterol and
triglycerids
OTHER TYPES OF SKIN TUMORS AND PROLIFERATIONS
 Histiocytosis X- the systemic patterns have been discussed, cutaneous form
presents as solitary or multiple papules or nodules in the skin
histologically- composed of Langerhans cells- mononuclear cells with bland
indented nuclei with variable admixture of eosinophilic leukocytes
 Mycosis fungoides (cutaneous T-cell lymphoma)- is a lymphoproliferative
disorder characterized by neoplastic cell infiltrates in the skin, if associated
with generalized T-cell leukemia- Sézary syndrome
grossly- MF presents as eczema-like lesions- scaly, red-brown patches or
plaques, and nodules- usually on the trunk, extremities face and scalp
histologically-presence of Sézary cell- neoplastic T lymphoid cells
 Mastocytosis- rare disorder characterized by cutaneous mast cell
proliferation, symptoms reflect histamine and heparin release, clinical
symptoms include pruritus, flushing, triggered by specific foods, temperature,
alcohol or certain drugs
 urticaria pigmentosa- is exclusively cutaneous form, occurs mostly in children
grossly- skin lesions are multiple, round-to-oval, red-brown papules,
microscopically composed of eosinophils, mast cells with fibrosis and edema
NON-TUMOROUS DISORDERS OF THE SKIN
-chronic inflammatory dermatoses
-acute inflammatory disorders
-blisters
-infections of the skin
–dermatoses of ticks
Chronic inflammatory dermatoses:
are persistent inflammatory disorders, lasting over several months to years
 Psoriasis- a common inflammatory cutaneuous disorder, etiology unknown,
genetic predisposition is likely, but a genesis of new lesions at the sites of
trauma suggests a possible role for exogenous stimuli, damage to the stratum
corneum may induce the deposition of complement-fixing antibodies with
secondary complement-mediated immune injury,
psoriasis may be associated with other diseases, such as enteropathies,
myopathies, rheumatoid arthritis, etc
grossly- lesions are well-demarcated, salmon pink, plaques with silvery
scaling- elbows, knees, scalp, lumbosacral area,
histologically- marked acanthosis with rete elongations, stratum granulosum
is absent, with extensive overlying parakeratosis, epidermis overlying dermal
papillae is thinned, aggregates of neutrophils in epidermis occur within stratum
spinosusm- Munro microabscesses
 Lichen planus- a self-limited disease, pathogenesis is unknown, cell-mediated
immune injury is likely
grossly- pruritic, purple papules, that may coalesce to plaques, they are
multiple, symmetrically distributed, often on the writs and elbows, oral mucosa
may be affected
histologically- there is a dense, band-like dermoepidermal junction
lymphocytic infiltrate with basal cell degeneration- basal cell die by apoptosisto form colloid or Civatte bodies
 Lupus erythematodes- two major variants -systemic LE, and discoid LElocalized cutaneous form of LE without systemic manifestation
pathogenesis is unknown, immune complex mediated or cell-mediated
immune injury is suspected
grossly- skin lesions of both SLE and DLE include ill-defined erythematous
scaling plaques with zones of irregular pigmentation
histologically- DLE is characterized by dermoepidermal junction,
perivascular and periapendical lymphocytic infiltrates, subcutaneus tissue may
be also infiltrated
 acne vulgaris- a common chronic inflammatory dermatosis affecting hair
follicles, typically in the middle to late adolescence, more severe in men than
in girls, pathogenesis is speculative, heritable component is included, the
lesions are however triggered by sex hormone stimulation, and bacterial
infection also seems to participate (Propionibacterium acnes)- this bacterium
causes lipase degradation of sebaceous oils, thus highly irritative fatty acids
appear, antibiotics may be effective by inhibiting the lipase activity, the
vitamine A derivates are also partly effective in therapy
grossly-acne is characterized by open comedones (follicular papules with
central plug trapped beneath the epidermis and therefore not visible),
inflammatory acne shows erythematous papules nodules and pustules
histologically- comedones are composed of lipid and keratin deposits within
the midportion of hair follicles with follicle dilatation and epithelial and
sebaceous gland atrophy
-there is variable lymphohistiocytic infiltrate, and the chronic extensive
inflammation may cause scar formation
acute inflammatory disorders
-are characterized by short-lived lesions (days to weeks) marked by
lymphocytic infiltrate with edema and local tissue damage
 Urticaria (hives)- a common disorder characterized by focal mast cell
degranulation, with histamine-mediated dermal pruritus, edema, and wheal, it
occurs in young adults,
histologically-sparse lymphocytic perivascular infiltrate with edema, most
lesion are mediated by antigen-specific IgE, that results in degranulation of
mast cells in sensitive patients
 Acute eczematous dermatitis- a group of pathogenetically different
conditions with similar histological features, five major types of eczema exist,
contact dermatitis (caused by local contact with irritative chemicals), atopic
dermatatis (heritable immune-mediated dermatitis), drug-related eczematous
dermatitis (caused by systemic administration of certain drug, such as
penicilin), photoeczematous eruptions (caused by UV light in sensitive
persons), and primary irritant dermatitis (repeated trauma)
grossly- all types of acute eczema are pruritic, red, papulovesicular lesions
with blistering, in chronic lesions- scaling plaques
microscopically-spongiosis
with
progressive
fluid
accumulationintraepidermal vesicles, dermal perivascular lymphocytic infiltrate
blisters:
-these are primary blistering disorders, the level of blister formation is
critical for diagnosis (subcorneal, suprabasal, subepidermal, intraepidermal)
 pemphigus- rare autoimmune disorder, typically occurs in 4.-6.decades,
characterized by circulating antibodies to keratinocytes, it involves oral
mucosa, face, scalp, trunk, etc, if untreated it is fatal
grossly-superficial easily ruptured blisters, that leave shallow crusted
erosions
micro-acantholyis leading to intercellular clefting- and intraepidermal
blisters
 dermatitis herpetiformis- a rare disorder typically in the 3.-4.decades, in
males more common, associated with specific HLA types, DH is presumably
mediated either by immune complex deposition in the skin, or by antibodies to
gliadin (protein of gluten-DH may be associated with celiac disease and may
respond to gluten-free diet)- that cross-reacts with junctional anchoring
components in the basement membrane of the skin
-presence of granular IgA deposits in the dermal papillae tips is
characteristic
histologically- neutrophils and fibrin accumulates in the tips of dermal
papillae-subepidermal blisters
 porphyria-is non-inflammatory blistering disorder, is a group of inborn or
acquired disturbances of porphyrin metabolism, the cutaneous lesions consists
of urticaria and vesicles that are triggered by sun exposure and heal without
scarring, histologically- subepidermal vesicles and blisters
skin infections
 Warts (Verruca)- common spontaneously regressing lesions, typically in
children and adolescents, caused by HPV transmitted by direct contact
types 6, 11, 16, and 18 are associated with anogenital warts, type 16 and 34
may cause dysplasia.
verruca vulgaris (common wart)-most common, most frequently on the hand,
grey to white flat to convex papule with rough surface
verruca plana (flat wart)- on the face or dorsum of the hand, uterine
cervix, flat tan-coloured papule with smooth surface
verruca plantaris (soles) and palmaris (palms)- rough scaly lesions
condyloma accuminatum (anogenital and venereal warts)- soft tan masses up
to several centimeters in diameter
histologically- all warts are characterized by epidermal hyperplasia and
superficial keratinocyte perinuclear vacuolization (koilocytosis)- elmi-reveals
numerous viral particles within koilocytes
 molluscum contagiosum- common, self-limited disease caused by poxvirus
transmitted by direct contact
grossly- pruritic pink papule seen on the trunk, or anogenital region
micro-verrucous cuplike epidermal hyperplasia with molluscum bodies-large
eosinophilic cytoplasmic inclusions in the stratum granulosum-represent virions
 impetigo- streptococcal or staphylococcal skin infection seen in normal
children especially on the face and hands (rarely may affect sick adults), it
begins as an erythematous macule that progresses to small pustules and
erosions-with honey-coloured crust
histologically- subcorneal pustules filled with neutrophils
dermatoses from ticks
-ticks are ectoparasites that cause dermatologic disease directly by their bites
and indirectly as vectors of bacterial, viral, protozoal and ricketssial diseases
tick bites cause a variety of acute and chronic skin lesions
-tick-borne diseases include Lyme disease, tick-borne relapsing fever,
tularaemia, Rocky Mountains spotted fever, and others
 Lyme disease is the most common vector-born skin disease- over the last
decade, knowledge about pathobiology, molecular immunology and clinical
course of Lyme disease has expanded rapidly
-Lyme disease is caused by borrelia (Burgdorferi in the U.S., and B.
afzelii and B. garinii in Europe and Asia), microorganism transmission is unlikely
when ticks are removed within 24 h. of attachment
-Lyme d. occurs in stages with different clinical manifestation in each
stage
stage 1- localized infection, erythema migrans is seen in most patients,
headache, fatigue, malaise, arthralgias, in few lymphadenopathy
stage 2- disseminated infection-within days to weeks after inoculationmultisystem involvement- migratory pains in joints, tendons, muscles, bones,
neurological problems include meningitis, motor and sensory palyradiculopathy
stage 3- late and persistent infection- acrodermatitis chronica
atrophicans, fibrotic nodules, sclerotic and atropohic skin lesions, such as lichen
sclerosus et atrophicus