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  • A macule is a small, flat, distinct, colored area of skin that is less than 10 millimeters in diameter, and does not include a change in skin texture or thickness.
    A papule is a skin lesion that is small, solid, and raised.
    Reye's syndrome (RS) is primarily a children's disease, although it can occur at any age. It affects all organs of the body but is most harmful to the brain and the liver--causing an acute increase of pressure within the brain and, often, massive accumulations of fat in the liver and other organs. RS is defined as a two-phase illness because it generally occurs in conjunction with a previous viral infection, such as the flu or chicken pox. The disorder commonly occurs during recovery from a viral infection, although it can also develop 3 to 5 days after the onset of the viral illness. RS is often misdiagnosed as encephalitis, meningitis, diabetes, drug overdose, poisoning, sudden infant death syndrome, or psychiatric illness. Symptoms of RS include persistent or recurrent vomiting, listlessness, personality changes such as irritability or combativeness, disorientation or confusion, delirium, convulsions, and loss of consciousness. If these symptoms are present during or soon after a viral illness, medical attention should be sought immediately. The symptoms of RS in infants do not follow a typical pattern; for example, vomiting does not always occur. The cause of RS remains a mystery. However studies have shown that using aspirin or salicylate-containing medications to treat viral illnesses increases the risk of developing RS.
  • zosterFunction: nounEtymology: Latin, from Greek zOstEr girdle; akin to Greek zOnE zone: SHINGLES
    Post-herpetic neuralgia is constant pain or periods of pain that can continue after the skin has healed. It can last for months or even years and is more common in older people. The use of medication in the early stages of the zoster may help prevent this complication.
    Since shingles occurs in an area of the skin that is supplied by sensory fibers of a single nerve--called a dermatome--the rash usually appears in a well-defined band on one side of the body, typically the torso; or on one side of the face, around the nose and eyes. (Shingles' peculiar name derives from the Latin cingulum, which means girdle or belt.) If a diagnosis is in doubt, lab tests can confirm the presence of the virus.
  • Onychomycosis, also referred to as fungal nails or tinea unguium, is a common and annoying condition for many adult patients. The disease is characterized by a gradual thickening of the nails with an accompanying change in color of the nail plate.The condition can be caused by fungi, yeast or mold, but the most common causative agent is the fungi trichophyton. Predisposing damage or trauma to the nail plate can give the fungi an unfair advantage in infecting the nail. This, combined with the warm moist enviroment of shoes allows the fungi to live in the perfect breeding ground.
    The prevalence of this condition dramatically increases with age. Twenty percent of people over the age of 60 are affected with this condition, while one-third of the entire diabetic population can expect to come in contact with this condition during their lifetime. Patients at high risk for the development of onychomycosis include people who are HIV positive, those undergoing immunosuppressive therapy and those with conditions that cause the immune system to become compromised.
    Signs and Symptoms
    Onychomycosis typically presents with discolored nails, mostly of a yellowish hue and thickening of the nails. Some patients describe their nails as beginning to grow up more than out. Debris can be found beneath the nail plate, which is a good medium for fungi to thrive. Fungi favor warm and moist environments, which is typical inside a shoe.
  • Scabies is a disease of worldwide importance caused by burrowing of the parasitic mite Sarcoptes scabiei into the lower stratum corneum of the epidermis. Infestation with Sarcoptes scabiei causes an allergic type skin reaction with visible hypersensitivity lesions and pruritus and results in significant morbidity primarily due to secondary infections with pathogenic bacteria. Until very recently there were no molecular studies on scabies because of the difficulty of obtaining mites. We have solved this problem by constructing a library of expressed Sarcoptes scabiei sequences from mites obtained from skin shed into the bedding of patients with the severe form of the disease, crusted scabies.
  • What is Chlamydia trachomatis?
    Chlamydia trachomatis is a small bacterium that cannot grow outside a living cell. In this respect it resembles a virus, but it is actually a very sophisticated organism. There are two other related organisms: Chlamydia psittaci is widespread in animals and can be transmitted to humans. This organism in humans is an uncommon cause of severe pneumonia particularly when acquired from infected birds of the parrot (Psittacine) family, and occasionally of abortion following contact with infected sheep. The more recently described Chlamydia pneumoniae (also known as the TWAR agent - Taiwan Acute Respiratory, after the designations of the first two isolates), may prove to be a frequent cause of upper and lower respiratory infection transmitted from person to person by infected droplets.
    Which diseases does it cause?
    Worldwide, the most important disease caused by Chlamydia trachomatis is trachoma, one of the commonest infectious causes of blindness. In some parts of the developing world, over 90% of the population becomes infected. However, the specific strains of Chlamydia trachomatis which cause trachoma and the epidemiological conditions for its spread, are not found in the UK. In Britain, the organism often causes genital tract infection. In men, Chlamydia trachomatis is the commonest cause of non-gonococcal or (less correctly) non-specific urethritis. In women, the organism may infect both the cervix and the urethra. Epididymitis may complicate infection in men, whilst in women infection in the upper genital tract - the endometrium and the fallopian tubes, may lead to acute pelvic inflammatory disease (PID). Chlamydia trachomatis is the most frequent cause of PID and its long term consequences include chronic pain, ectopic pregnancy and infertility. In both sexes, conjunctivitis (that does not progress to blindness) and joint inflammation may occur.
    Babies born to mothers with infection of their genital tract frequently present with chlamydial eye infection within a week of birth (chlamydial ophthalmia neonatorum), and may subsequently develop pneumonia.
    What are the symptoms and signs?
    Symptoms and signs are non-specific, and variable. In men, a mucopurulent urethral discharge, with or without pain on passing urine appears between one and three weeks after exposure. In women, cervical infection may produce vaginal discharge. It is impossible to exclude other genital infections such as gonorrhoea or bacterial vaginosis on clinical examination alone and laboratory examination of the discharge is essential to make the diagnosis. Mixed infections are common.
    In both men and women, asymptomatic infection is not uncommon.
    Abdominal pain and raised temperature may indicate PID in women. This condition may be difficult to distinguish from other causes of abdominal pain.
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    1. 1. Copyright © 2010 Pearson Education, Inc. Lectures prepared by Christine L. Case Chapter 21 Microbial Diseases of the Skin and Eyes Part 2: Viral, Fungal, and Parasitic Skin Infections
    2. 2. Copyright © 2010 Pearson Education, Inc. Expected Student Learning Outcomes List the causative agent, mode of transmission, and clinical symptoms of these skin infections: 1. warts 2. smallpox 3. monkeypox 4. chickenpox 5. shingles 6. cold sores 7. measles 8. rubella
    3. 3. Copyright © 2010 Pearson Education, Inc. Expected Student Learning Outcomes cont.  Differentiate cutaneous from subcutaneous mycoses, and provide an example of each.  List the causative agent and predisposing factors for candidiasis.  List the causative agent, mode of transmission, clinical symptoms, and treatment for scabies and pediculosis.  Define conjunctivitis.  List the causative agent, mode of transmission, and clinical symptoms of these eye infections: ophthalmia neonatorum, inclusion conjunctivitis, trachoma.  List the causative agent, mode of transmission, and clinical symptoms of these eye infections: herpetic keratitis, Acanthamoeba keratitis.
    4. 4. Copyright © 2010 Pearson Education, Inc. Viral Diseases of the Skin Cryotherapy (liquid N2) Imiquimod (stimulates interferon production) Electrodesiccation Bleomycin Burn off with acid Lasers Warts  Papillomaviruses  cause skin cell proliferation ⇒ benign growth named wart or papilloma.  Spread by direct contact  May regress spontaneously or be removed chemically or physically via
    5. 5. Copyright © 2010 Pearson Education, Inc. Smallpox  Smallpox virus (orthopox virus). Two types: variola major (> 20% mortality); variola minor (since 1900; < 1% mortality)  Respiratory transmission. Virus moved to skin via bloodstream.  Human only host  From macules to papules to vesicles to pustules → reminiscent of ______  Pitted scars = pocks  Jenner  Eradicated due to vaccination effort by the WHO  Bioterrorism  Monkeypox Prevention by smallpox vaccination
    6. 6. Copyright © 2010 Pearson Education, Inc. Chickenpox (VZV or HHV-3 Varicella–zoster or human herpes virus 3 of Hepesviridae family Respiratory transmission ⇒ to blood ⇒ to skin (⇒ to sensory neuron) Macule to papule to vesicle to pustule in 24 h Pruritic (itchy) lesions – scratching may lead to serious 2° infections (S. pyogenes and S. aureus) Complications: encephalitis and Reye’s syndrome. After chickenpox, virus can remain latent in nerve cells. Reactivation later → shingles = Herpes zoster (characteristic vesicular rash along affected cutaneous sensory nerves.) Treatment with acyclovir.
    7. 7. Copyright © 2010 Pearson Education, Inc. Chickenpox Vaccine  1995: attenuated chickenpox vaccine | released in US (Varivax)  2001: mandated in CA for kindergarten and school  85% effective  Breakthrough varicella in vaccinated people  Chickenpox vaccine being proposed for older adults to prevent ___________
    8. 8. Copyright © 2010 Pearson Education, Inc. Virus may remain latent in dorsal root ganglia Occurrence of shingles when cell mediated immunity weak. After healing may result in chronic pain → Post- herpetic neuralgia (may last for years) Fig 21.11b
    9. 9. Shingles or Herpes Zoster About 20 % of people who have had chicken pox will get zoster at some time during their lives. Most people will get zoster only once.
    10. 10. Copyright © 2010 Pearson Education, Inc. Herpes Simplex Types 1 and 2  Herpes simplex virus 1 (HSV type 1) and 2 (HSV type 2); ds DNA, enveloped; of Herpesviridae family  New name: Human herpes virus 1 (HHV-1) and 2 (HHV-2)  HSV-1 can remain latent in trigeminal nerve ganglia  HHV-2 can remain latent in sacral nerve ganglia.  Acyclovir, vidarabine generally lessen symptoms  Very common, recurrent infection often during childhood (fever, blisters, cold sores) > 90% of Americans exposed
    11. 11. Copyright © 2010 Pearson Education, Inc. HSV-1 in the Trigeminal Nerve Ganglion Figure 21.13
    12. 12. Copyright © 2010 Pearson Education, Inc. Manifestations of HSV 1 and 21. Cold sores or fever blisters (vesicles on lips) 2. Herpes gladiatorum (vesicles on skin) 3. Herpetic whitlow (vesicles on fingers) 4. Herpes encephalitis : Via olfactory nerve. Up to 70% fatality rate with HHV-2 5. Neonatal herpes passage though infected birth canal (→ encephalitis). May also cross placenta. 6. Genital herpes - Type II may increase risk of cervical cancer Transmitted through contact with oral secretions from an individual who is obviously infected . . . or asymptomatic(!) Herpes labialis
    13. 13. Copyright © 2010 Pearson Education, Inc. Herpetic Whitlow  Occupational hazard for health care professionals.  Intense painful infection of the hand involving 1 or more fingers, typically terminal phalanx (60% HSV-1; 40% HSV-2)
    14. 14. Copyright © 2010 Pearson Education, Inc. Measles (Rubeola)  Measles virus  Transmitted by respiratory route  Macular rash and Koplik's spots on oral mucosa.  Complications of measles:  middle ear infections, pneumonia, and secondary bacterial infections.  Encephalitis in 1 in 1,000 cases  Subacute sclerosing panencephalitis in 1 in 1,000,000 cases Fig 21.14
    15. 15. pathognomic of measles ! Typically involve the buccal and labial mucosa. Irregular, patchy erythema with tiny central white specks → 'grains of salt‘ appearance. Koplik Spots
    16. 16. Measles Prevented by attenuated vaccine (MMR) Reported U.S. Cases of Measles, 1960–2007: Clinical Focus, p. 505
    17. 17. Copyright © 2010 Pearson Education, Inc. Rubella - German Measles Caused by rubella virus Typically mild (macular rash, fever), often unrecognized Teratogenic during early pregnancy (congenital rubella syndrome) Attenuated vaccine (MMR)
    18. 18. Copyright © 2010 Pearson Education, Inc. Diseases in Focus: Vesicular and Pustular Rashes p. 589  An 8-year-old boy has a rash consisting of vesicular lesions of 5 days’ duration on his neck and stomach. Within 5 days, 73 students in his elementary school had illness matching the case definition for this disease.  Can you identify infections that could cause these symptoms?
    19. 19. Copyright © 2010 Pearson Education, Inc. Fungal Diseases of Skin and Nails  Cutaneous mycosis  Subcutaneous mycoses  Candidiasis
    20. 20. Copyright © 2010 Pearson Education, Inc. Cutaneous Mycoses – Dermatomycoses Also known as tineas or ringworm Microsporum, Trichophyton, and Epidermophyton colonize the outer layer of the epidermis Metabolize keratin ⇒ grow on keratin-containing epidermis, hair, skin, and nails. Diagnosis based on microscopic examination of skin scrapings or fungal culture. Dermatomycoses usually treated with topical chemicals (e.g.: Miconazole) or oral griseofulvin
    21. 21. Tinea unguium
    22. 22. Copyright © 2010 Pearson Education, Inc. Subcutaneous Mycoses More serious than cutaneous mycoses Sporotrichosis (rose gardener’s disease) results from soil fungus (Sporothrix schenkii ) that penetrates the skin through a wound. The fungi grow and produce subcutaneous nodules along the lymphatic vessels. Treated with potassium iodide (KI) If untreated may persist for years.
    23. 23. Copyright © 2010 Pearson Education, Inc. Candidiasis  Candida albicans (yeast)  May result from suppression of competing bacteria by antibiotics  Occurs in skin; mucous membranes of genitourinary tract and mouth.  Topical treatment with miconazole or nystatin.  Thrush: An infection of mucous membranes of mouth
    24. 24. Copyright © 2010 Pearson Education, Inc. Parasitic Skin Infections Scabies mites  Sarcoptes scabiei burrowing and laying eggs in skin.  Intimate contact transmission  Secondary infections common due to scratching  Treatment with topical insecticides, or oral ivermectin Pediculosis  caused by louse (Pediculus humanus)  Feed on blood.  Lay eggs (nits) on hair.  Treatment with topical insecticides.
    25. 25. Copyright © 2010 Pearson Education, Inc. Bacterial Diseases of the Eye Infection of the Eye Membranes: Conjunctivitis (pinkeye) Various bacteria (e.g.: Haemophilus influenzae, pseudomonas) and viruses (e.g.: adenovirus) Inclusion conjunctivitis: caused by Chlamydia trachomatis. Transmitted to infants during birth and through unchlorinated swimming water. Conjunctivitis also associated with unsanitary contact lenses
    26. 26. Copyright © 2010 Pearson Education, Inc. Neonatal Gonorrheal Ophthalmia Causative agent: Neisseria gonorrhoeae Transmitted to a newborn's eyes during passage through the birth canal. Original preventative treatment with silver nitrate. Now replaced with antibiotics due to common coinfection with Chlamydia.
    27. 27. Copyright © 2010 Pearson Education, Inc. Caused by 4 trachoma serotypes of Chlamydia trachomatis Infections of conjunctiva leads to nodule formation 5-10% of the world's population has been infected (esp. in hot, dry regions) Worldwide leading cause of nontraumatic blindness in children Typically infected during birth or autoinoculation from extra-ocular sites Trachoma
    28. 28. Copyright © 2010 Pearson Education, Inc. Other Infectious Diseses of the Eye Herpetic Keratitis (Inflammation of the cornea)  Herpes simplex virus 1 (HSV-1)  Leading cause of infectious blindness in US  Can recur  Treated with trifluridine Acanthamoeba Keratitis protozoa transmitted via water, contact solutions
    29. 29. Copyright © 2010 Pearson Education, Inc. Diseases in Focus: Microbial Diseases of the Eye p. 604  A 20-year-old man had eye redness with dried mucus crust in the morning. The condition resolved with topical antibiotic treatment.  Can you identify infections that could cause these symptoms? The EndThe End