Lecture by : Dr Sahar Hegazy

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Lecture 1
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Introduction
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Introduction

• Dermatology
• is the science deal with skin and its diseases.
• Skin is considered as the mirror for internal
  organs. Many internal diseases can be discovered
  by skin eruption as a clue for diagnosis.

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Skin Structure

• - The skin is composed of two layers
• the epidermis and the dermis.
• -The epidermis is the outer layer and has
  appendages (hair, nails, sebaceous glands and
  sweat glands).
• -The dermis is the inner layer.

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The epidermis

• - The epidermis is multilayered structure which
  renews itself continuously by cell division in
  its deepest layer.
• - The principal cell type, the epidermal cell, is
  most commonly referred to as keratinocyte. The
  cells produced by cell division in the basal
  layer constitute the prickle cell layer and as
  they ascend towards the surface they undergo a
  process known as keratinization which involves
  the synthesis of fibrous protein keratin.

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• - A typical cell takes approximately 30 days to
• pass from the basal layer to the surface of the
• epidermis.
• The cells on the surface of the skin are fully
• keratinized dead cells which are gradually
  abraded by day to day wear and tear from
  environment. If you bathe after a period of
  several days deprivation of contact with water,
  you will notice that you towel yourself your are
  rubbing off small balls of keratin.

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Hair and sebaceous glands

• - Hair grows out of tubular invaginations of the
  epidermis known as follicles. Hair pigment is
  produced by melanocytes.
• - Hair has a central core (medulla) which is
  covered by the cortex then the cuticle.
• - The growth of hair is cyclical periods of
  active growth (anagen) alternate with resting
  phases (telogen).
• - At any time approximately 85 of scalp hairs
  are in anagen, and 15 in telogen. The average
  number of hair shed daily is 100.

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Sebaceous glands

• - Sebaceous glands are found everywhere on the
  skin apart from the palms of the hands and the
  soles and dorsa of the feet.
• - Their lipid-rich secretion (sebum) flows
  through a duct into the hair follicle.

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Nail

• - A nail is a transparent plate of keratin.
• - Nail growth is continuous through life and
  there
• are many factors can affect nail growth rate.
• Sweat glands
• - They are important in body temperature
  regulation. They secrete water and electrolytes,
  lactate, urea and ammonia.
• - The secretory coil produces isotonic sweat but
  sodium chloride is reabsorbed in duct so that
  sweat reaching the surface is hypotonic.

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The dermis

• - It's the layer of connective tissue lying
  beneath the epidermis and forming the bulk of the
  skin.
• - Fibroblasts, mast cells and macrophages
  constitute the main cellular elements of the
  dermis.
• - The dermis is also rich with blood vessels,
  lymphatics, nerves and sensory receptors.

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Function of the skin

• 1- It protects the body against the entry of
  toxic environmental chemicals, as well as
  from damage from UV radiation.
• 2- It regulates the body temperature
• 3- It contributes to the body supply of vitamin D
• 4- Excretory function through sweating to get rid
  of urea and other waste products.
• 5- It is a sensory organ contain nerve endings
  for all modalities of sensation including
  heat , cold and pain.

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Dermatological diagnosis

• 1- History taking
• It includes the duration of the disease,
  the first site affected, mode of spread,
  itching, seasonal variation, family history,
  pervious treatment.
• 2- Examination
• 1- The patient must be undressed, and
  examined under good light.
• 2- Identification of the initial lesion
• 3- The distribution of the lesions.

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• 3- Investigation
• - Blood tests
• - Skin biopsy (histopathological examination)
• Dermatological lesions
• -Primary lesion the first lesion appears.
• -Secondary lesion occurs as a result of
  bacterial invasion or trauma, or alteration of
  the primary lesion.

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Primary lesion

• Macule flat, circumscribed area of skin, may be
  hyperpigmented, hypopigmented, depigmented,
  erythmatous or pruritic.
• Papule a small elevation over the skin (lt 1cm in
  diameter) It varies in colour, may be red, brown
  ...
• Nodule Larger than the papule.
• Plaque an elevated skin area gt 2 cm in diameter,
  extension of papule or nodule.

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• Vesicle a small collection of fluid (lt 1cm in
  diameter) .
• Bulla a large collection of fluid.
• Pustule collection of pus.
• Burrow It is a characteristic lesion of scabies,
  irregular linear elevation over the surface of
  the skin, very pruritic.

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• Secondary lesions
• Crust accumulated dried exudates.
• Ulcer localized loss of dermis as well as
  epidermis.
• Scar fibrous tissue replacement of skin after
  healing of defects or ulcers.

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Bacterial InfectionCellulitis

• - It is an infection of the skin and subcutaneous
  tissue by streptococcal pyogenes.
• - The legs are the common site for cellulitis,
  but other parts of the body including the face
  may be affected.
• - The organism gain entry into the skin via
  minor abrasions.
• Clinical picture
• - The affected area becomes erythematous,
  hot, and swollen.

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Treatment- Strict bed rest.- Parentral
penicillin, cephalosporin, erythromycin, or
ciprofloxacin.

• Pharmacotherapy considerations
• 1- Penicillins, cephalosporins and erythromycin
• are safe in pregnancy, however ciprofloxacin
• are contraindicated (cartilage erosion).
• 2- Drugs require dose adjustment in renal
  failure
• All penicillins excepy nafcillin and oxacillin
• All cephalosporins except cephoperazone and
  cephotriaxone.
• All floroquinolones.
• 3- Erythromycins can be taken safely in renal
  failure but it's contraindicated in
  liver disease.

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Folliculitis

• - It is an infection of the superficial part of
  the hair follicle with Staph. aureus.
• Clinical picture
• - It produce small pustule on an erythematous
  base, centered on the follicle.
• Treatment
• It can be treated with topical antibacterial
  agent, but a systemic antibiotic may be required.

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Impetigo

• - It is a superficial infection of the skin
  caused by staph. aureus (bullous) or
  streptococci (non-bullous).
• Clinical picture
• Bullous impetigo
• - It appears as vesicles and bulla on normal
  skin, commonly on trunk, face, hands and
• intertriginous area.

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• Non- Bullous impetigo
• - It occur on the face, arms, legs and scalp
  as erythematous lesion which develop
  pustule that rupture to leave exuding
  surface which dried to form golden yellow
  crust.
• It may occur secondary to scabies, head -
  louse infestation or insect bite.

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• Types
• 1- Bullous impetigo.
• 2- Circinate impetigo.
• 3- Bokhart's impetigo.
• 4- Streptococcal intertrigo.
• 5- Ecthyma

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Treatment

• 1- Removal of the crust by warm compressor
  using antiseptic solution as potassium
  permanganate solution.
• 2- Topical antibacterial agent as sodium fusidate
  or tetracycline.
• 3- Systemic
• Ampicillin, amoxicillin (250 -500 mg/6hr)
• Erythromycin (250 mg/6 hr)
• Cephalexin (250 -500 mg/6hr)

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Leprosy

• - It is bacterial infection caused by
  mycobacterium leprae.
• - It is a disease of peripheral nerves, but it
  also
• affects the skin, and sometimes other tissues
  as
• the eyes, the mucosa of the respiratory tract,
  the
• bones and the testes.
• - The incubation period is lengthy (several
  years) and it likely that most patients
  acquire the
• infection in childhood.
• - The disease is acquired as a result of close
• prolonged contact with an infected person.

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• - The clinical pattern of the disease is
  determined by the host's cell-mediated immune
  response to the organism.
• When it's well-developed (high cell-mediated
  immunity) the pattern of the disease is
  tuberculoid leprosy, in which
• the skin and peripheral nerves are affected.
• Skin lesions are single or few in number (1-3).
• They are macules or plaques which are hypo-
  pigmented in dark skin.
• The lesions are anesthetic.

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• The peripheral nerves are thickened and
  cord-like with loss of sensation.
• Lepromin test is strongly positive.
• Histology shows well-defined tuberculoid
  granulomas and bacilli are not seen on
  staining.

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• When the cell-mediated immune response to the
  bacilli is poor, the pattern of the disease is
  lepromatous leprosy, in which
• It involves not only the skin but also, the
  eyes, the mucosa of the respiratory tract, the
  bones and the testes.
• The skin lesions are multiple and nodular, and
  symmetrically distributed.
• If it is on the face, it give lionine face
  (characteristic features)
• Lepromin test is negative.
• Histology shows diffuse granulomas and
  bacilli are present in large numbers.

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• Borderline leprosy
• It has a combined feature of both polar types
  (LL and TL), so the immunity of the patient,
  number of lesions, and anesthesia is intermediate
  between LL and TL.
• Treatment
• Multidrug therapy
• -Dapsone 100 mg/day
• -Rifampicine
• -Ofloxacin