Dermatology 5th year, 2nd lecture (Dr. Mohammad Yousif)


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The lecture has been given on Dec. 19th, 2010 by Dr. Mohammad Yousif.

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Dermatology 5th year, 2nd lecture (Dr. Mohammad Yousif)

  1. 1. Pruritus “Itching”<br />
  2. 2. Pruritus<br /><ul><li>Itching is an unpleasant sensation that provokes the desire to scratch.
  3. 3. It is the most common symptom of inflammatory skin diseases.
  4. 4. An essential characteristic of itch is that the only peripheral tissue from which it can be evoked is skin, with the single exception of cornea.</li></li></ul><li>Pruritus<br />With primary skin lesions<br />e.g. macules, wheals, papules, plaques, vesicles, etc.<br />Diagnose the skin disease<br />Localized<br />LP, eczemas, scabies, etc.<br />Generalized<br />Urticaria, drug eruptions, erythroderma, xerosis, etc.<br />
  5. 5. Pruritus<br />Without primary skin lesions<br />But with secondary skin lesions, e.g. ulcer, excoriations, lichenification, hyperpigmentation, etc.<br />Generalized pruritus without 1ry skin lesions<br />Manifestations of syst. dis.<br />Generalized idiopathic pruritus<br />
  6. 6. Causes of<br />Pruritus<br />
  7. 7. Causes of pruritus<br />I) Pruritus from skin diseases<br />These diseases often have characteristic lesions and locations. However, rubbing and scratching may conceal the primary lesions.<br />
  8. 8. I) Pruritus from skin diseases (Cont’d)<br />A) Severely pruritic dermatoses<br />Scabies / phthirus pubis<br />DH<br />LP<br />Urticaria<br />Contact dermatitis<br />Atopic dermatitis<br />Drug eruptions<br />PUPP of pregnancy<br />Herpes gestationis<br />Mycosis fungoides<br />No scratch marks<br />10<br />
  9. 9. I) Pruritus from skin diseases (Cont’d)<br />B) Moderately pruritic dermatoses<br />Seb. Dermatitis.<br />Polymorphous light eruption.<br />Urticaria pigmentosa.<br />Fungal infections.<br />Asteatotic eczema (xerosis): aggravated by low humidity during winter (winter itch).<br />5<br />
  10. 10. Causes of pruritus (Cont’d)<br />II) Exogenous causes of pruritus<br />Sunburn.<br />Chilblains.<br />Aquagenic pruritus.<br />Insect bites / animal mites.<br />Detergents / fiberglass.<br />5<br />
  11. 11. Causes of pruritus (Cont’d)<br />III) Systemic causes of pruritus:<br />Systemic causes of pruritus can be summarized by the mnemonic BLINKED.<br />
  12. 12. III) Systemic causes of pruritus (BLINKED) (Cont’d)<br />Blood disorders<br /><ul><li>Iron-deficiency anemia.
  13. 13. Polycythemia vera (50% of patients): classically, it follows a hot bath, with drop in temperature when the patient emerges from the bath, triggering the pruritus. It is pricking in nature and lasts 30-60 minutes.</li></li></ul><li>III) Systemic causes of pruritus (BLINKED) (Cont’d)<br />Liver diseases (cholestasis)<br /><ul><li>Biliary cirrhosis: 1ry or 2ry to carcinoma, chronic hepatitis C, pregnancy or drugs as chlorpropamide, phenothiazines and oral contraceptives. Pruritus may be due to bile salts or opioid peptides.
  14. 14. HCV: in patients with pruritus, 4% may have HCV.</li></li></ul><li>III) Systemic causes of pruritus (BLINKED) (Cont’d)<br />Infections / infestations<br /><ul><li>Parasitic: giardiasis, onchocerciasis, ascariasis.</li></li></ul><li>Pruritus without 1ry skin lesions<br />+<br />Peripheral eosinophilia<br />Drugs, parasites, atopy, lymphomas<br />
  15. 15. Psychogenic pruritus, in contrast to organic pruritus, DOES NOT awaken patients from their sleep<br />
  16. 16. III) Systemic causes of pruritus (BLINKED) (Cont’d)<br />Neoplastic<br /><ul><li>Hodgkin’s lymphoma (35% of patients suffered from pruritus, which may precede by 5 years).
  17. 17. Lymphomas, leukemias.
  18. 18. Internal malignancy.
  19. 19. Multiple myeloma.</li></li></ul><li>III) Systemic causes of pruritus (BLINKED) (Cont’d)<br />Neuropsychiatric<br /><ul><li>Emotional stress.
  20. 20. Delusions of parasitosis.
  21. 21. Neurotic excoriations.
  22. 22. Psychogenic pruritus, either generalized or localized, e.g. psychogenic anogenital pruritus.</li></li></ul><li>III) Systemic causes of pruritus (BLINKED) (Cont’d)<br />Endocrine disorders<br /><ul><li>DM: commonly anogenitalpruritus or pruritus vulvae secondary to candidiasis but rarely generalized.
  23. 23. Hyperthryoidism (4-11% of patients).
  24. 24. Hypothyroidism (2ry to xerosis).
  25. 25. Carcinoid syndrome.</li></li></ul><li>III) Systemic causes of pruritus (BLINKED) (Cont’d)<br />Drug reactions<br /><ul><li>Opiates, phenothiazines, aspirin, PUVA or antimalarias.</li></li></ul><li>Approaching<br />the<br />Pruritic Patient<br />
  26. 26. Approaching the pruritic patient<br />The approach to the patient with generalized pruritus without primary skin lesions is in the same manner as a patient with factitious dermatosis. Both are diagnoses of exclusion, i.e. all organic causes must be excluded within reasonable limits.<br />
  27. 27. 15 points<br />should be discussed<br />in the history<br />
  28. 28. Approaching the pruritic patient<br />1. Is the itching localized or generalized?<br /><ul><li>Duration of pruritus.
  29. 29. Duration of each attack.</li></li></ul><li>Approaching the pruritic patient<br />2. What sensation do you feel in your skin?<br /><ul><li>Itching.
  30. 30. Burning sensation.</li></li></ul><li>Approaching the pruritic patient<br />3. Is anyone else in your family affected? (Cont’d)<br /><ul><li>Only patient’s spouse “genital itching”
  31. 31. Phthirus pubis (after single exposure, > 1/3 patients have another STDs).</li></li></ul><li>Approaching the pruritic patient<br />4. Is therea relationship with occupation?<br /><ul><li>Chronic hand dermatitis or latex allergy
  32. 32. Healthcare workers.</li></li></ul><li>Approaching the pruritic patient<br />5. Is there any recent history of travel or sexual relations?<br />
  33. 33. Approaching the pruritic patient<br />6. Have you been exposed to any animal?<br /><ul><li>Domestic pets.
  34. 34. Animal mites.</li></li></ul><li>Approaching the pruritic patient<br />7. Any history of exposure to irritating chemicals, e.g. solvents or plants?<br />
  35. 35. Approaching the pruritic patient<br />8. How do you bath?<br /><ul><li>Excessive bathing dermatitis.
  36. 36. Hot water, harsh soap dryness dermatitis.
  37. 37. Bathing aquagenic itch.</li></li></ul><li>Approaching the pruritic patient<br />9. What cosmetics or fragrances do you use and have these changed recently?<br /><ul><li>Irritant or allergic dermatitis.</li></li></ul><li>Approaching the pruritic patient<br />10. What are you using on your skin to treat this condition?<br />
  38. 38. Approaching the pruritic patient<br />11. Have you started any new drugs in the past few months?<br /><ul><li>Adverse drug reactions.</li></li></ul><li>Approaching the pruritic patient<br />12. Do you scratch at night or wake-up scratching?<br /><ul><li>Nocturnal itching: systemic disease, scabies.
  39. 39. Psychogenic itching does not interfere with sleep.</li></li></ul><li>Approaching the pruritic patient<br />13. Have you been under a great deal of stress lately?<br />
  40. 40. Approaching the pruritic patient<br />14. Do you have a prior history of this type of itching? Is it recurrent?<br /><ul><li>Solar pruritus in summer.</li></li></ul><li>Approaching the pruritic patient<br />15. What exacerbates or alleviates?<br /><ul><li>Exacerbation by bathing, heat, dryness, physical exertion, …etc.
  41. 41. Alleviation by cooling.</li></li></ul><li>Approaching the pruritic patient<br />Physical examination<br /><ul><li>General condition.
  42. 42. Enlargement of LN, spleen, liver  lymphoma.
  43. 43. Rectal examination and pelvic examination (female)  malignancy.
  44. 44. Oral candidiasis  LN++  HIV.
  45. 45. Examine for excoriations and lichenification.</li></li></ul><li>Approaching the pruritic patient<br />Laboratory tests<br /><ul><li>Complete and differential blood count.
  46. 46. Renal function tests: urea, creatinine.
  47. 47. Liver function tests: alkaline phosphatase (best screening test), bilirubin. Serum antimitochondrial antibody test is highly sensitive and specific for diagnosis of primary biliary cirrhosis (PBC).
  48. 48. Thyroxine and TSH.
  49. 49. Feces for: parasites, occult blood (> 40 years).
  50. 50. Chest X-ray.
  51. 51. Fasting glucose.</li></li></ul><li>Pathophysiology<br />
  52. 52. Pathophysiology<br /><ul><li>Chemical and physical stimuli that cause itching appear to trigger free unmyelinated nerve endings that terminate at or near the dermoepidermal junction.
  53. 53. From there, the impulse is transmitted to the dorsal horn of the spinal column via unmyelinated C fibers and thin myelinated (A delta) fibers, across the midline and then in the lateral spinothalamic tract to the thalamus and finally to the sensory cortex.</li></li></ul><li>Pathophysiology<br />Although itching and pain travel along the same neural pathway, they are currently believed to be separate and distinct sensations for the following:<br /><ul><li>Itch elicits scratching; pain elicits a withdrawal.
  54. 54. Morphine relieves pain but can produce itching. Its antagonist “Naloxone” inhibits itch but lowers pain threshold.
  55. 55. Pruritic stimuli exert their action near or at the DEJ, while pain from deeper nerve endings in the skin.</li></li></ul><li>Mediators of itching<br />Histamine, proteases as trypsin, chymotrypsin & fibrinolysin & neuropeptides as substance P and vasoactive intestinal peptide (VIP), interleukin-2, opioid receptor, serotonin.<br />
  56. 56. Mediators of itching<br /><ul><li>Capsaicin: It is the spicy component present in the fruits and seeds of various species of capsicum (red pepper)  depletion of various neuropeptides especially substance P from the A-delta and C-nerve fibers  reversible suppression of axon reflexes in the skin (reducing pruritus).
  57. 57. Prostaglandin E1: they modulate pruritus rather than mediate it through lowering the threshold for histamine induced itch and potentiating the effect of other mediators.</li></li></ul><li>Types of itching<br />Application of a stimulus that causes itching results in 2 distinct responses:<br /><ul><li>“Spontaneous itch”: an itch that is well localized to the site of the stimulus and persists only briefly after the stimulus has been removed.
  58. 58. “Itchy skin”: a subsequent diffuse, poorly localized area surrounding the site of the stimulus that does not itch spontaneously but responds by intense itching when subjected to a light touch or other minor stimulus.</li></li></ul><li>Types of itching<br />The development of an urticarial wheal is associated with well-defined localized spontaneous itching, but a surrounding area of skin that responds with itching to any mild mechanical stimulus persists for hours, or even days after the wheal has subsided.<br />
  59. 59. Therapeutic approach<br />I) General recommendations<br />Diagnosis and treatment of underlying cause.<br />Prevention of scratching to stop the vicious cycle: the more the patient scratches, the greater the secretion of mediators  exacerbates pruritus.<br />
  60. 60. I) General recommendations (cont’d)<br />3. Practical recommendations for the pruritic patient:<br /><ul><li>Application of ointments and moisturizing creams having a fatty basis (as propylene glycol and wax esters) to preserve skin moisture and protect it from injury.
  61. 61. Avoid contact with pruritus-enhancing substances, e.g. very hot water   histamine secretion. Bathing should be in luke warm or cold water.
  62. 62. Avoid exposure to heat & excessive persipiration  stimulates C fibers which transmit pruritus.
  63. 63. Avoid alkaline soaps and irritative clothing as wool.</li></li></ul><li>Therapeutic approach<br />II) Topical treatment<br />1. Coolants:<br /><ul><li>Menthol 2%, affects delta-A fibers that transmit the sensation of cold.
  64. 64. Alcohol, phenol & camphor  local anesthetic effects.
  65. 65. Calamine lotion.</li></ul>2. Anesthetics: EMLA ointment, pramoxine.<br />3. Doxepin 5% cream in atopic dermatitis.<br />4. Steroids and liquid aspirin.<br />5. Capsaicin: it depletes neuropeptide substance P from unmyelinated C sensory neurons.<br />6. Crotamiton (Eurax).<br />
  66. 66. Therapeutic approach<br />III) Physical treatment<br />1. UVB is effective in uremic or hepatic pruritus.<br />2. Narrow-band UVB is effective in pruritus of atopic patients.<br />3. PUVA is effective in treatment of pruritus due to aquagenic pruritus and atopic dermatitis.<br />Phototherapy stabilizes mast cells preventing release of lymphokines from lymphocytes.<br />
  67. 67. Therapeutic approach<br />IV) Systemic treatment<br />1. Oral antihistamines<br />
  68. 68. Systemic ttt (oral antihistamines) (Cont’d)<br /><ul><li>H1-antihistamines are probably the most commonly prescribed antipruritic agents. Much of their activity stems from sedation, but some newer agents (e.g. cetirizine, loratidine or the 3rd class antihistamines as fexofenadine “Telfast” 180mg) may display anti-inflammatory activity that complements their histamine receptor blockade.</li></ul>To relieve itching, they may be used alone as in urticaria, or with other medications, e.g. topical steroids in atopic dermatitis, antiscabitics in scabies or antifungals in tineacruris.<br />
  69. 69. Systemic ttt (oral antihistamines) (Cont’d)<br /><ul><li>H2-antagonists, e.g. cimetidine in polycythemia vera.
  70. 70. Combinations of H1 and H2-antagonists in chronic urticaria.</li></li></ul><li>IV) Systemic ttt (Cont’d)<br />2. Aspirin in polycythemiavera.<br />3. Danazol: in pruritus with myeloproliferative disorders.<br />4. Systemic steroids: are excellent anti-inflammatory agents but do not provide itch relief in non-inflammatory itching conditions, e.g. renal or hepatic diseases.<br />5. Antidepressivetricyclic:Doxepin.<br />6. Opiate antagonists:Naltrexone.<br />7. Serotonin receptor antagonists:Ondansetron (antiemetic), cholestyramine.<br />8. IV propofol (new hypnotic).<br />
  71. 71. Therapeutic approach<br />V) Special conditions<br />1. Hepatobiliary pruritus<br /><ul><li>Rifampin.
  72. 72. Cholestyramine (Questran).
  73. 73. Naloxone (opiate antagonist – Naxone).
  74. 74. Propofol (Diprivan).</li></li></ul><li>Therapeutic approach<br />V) Special conditions (Cont’d)<br />2. Uremic pruritus<br /><ul><li>Oral activated charcoal.
  75. 75. Oral cholestyramine.
  76. 76. Heparin.
  77. 77. Thalidomide.
  78. 78. Erythropoietin.
  79. 79. UVB.
  80. 80. Renal transplant.</li>