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Soutor 1e- Clinical Dermatology- Lecture 3- Common Skin Infections and Infestations
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Soutor 1e- Clinical Dermatology- Lecture 3- Common Skin Infections and Infestations
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Upload Date:
2022-04-01T00:00:00.0000000
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Language: EN.
Segment:0 .
Segment:1 1. Infections and Infestations of the Skin.
DR. BART: I am Dr. Bruce Bart, Clinical Professor of Dermatology at the University of Minnesota, and Chief of Dermatology at Hennepin County Medical Center.
Segment:2 2. Learning Objectives.
DR. BART: I will be discussing with you selected infections and infestations of the skin, as listed here.
Segment:3 3. Fungal Infections.
DR. BART: Superficial cutaneous fungal infections are caused by dermatophytes or yeasts.
Segment:4 4. KOH (Potassium Hydroxide) Examination and Fungal Cultures.
DR. BART: A simple and quick microscopic test using KOH, potassium hydroxide, may help to identify whether a fungus infection is present.
DR. BART: Skin scales from the eruption are placed on a glass slide, and a 20% KOH solution is applied to this. Examination under the microscope can identify the branching fungal hyphae for dermatophyte infections or pseudohyphae and spores for yeast infections. Dermatophyte hyphae are seen in Figure 1. Cultures can also be taken from skin scrapings. A DTM culture medium, as demonstrated in Figure 2, turns a red color with dermatophyte infection.
Segment:5 5. Dermatophyte Infections.
DR. BART: There are several clinically distinct dermatophyte infections, depending on the location of the infection that is listed below.
Segment:6 6. Tinea Capitis.
DR. BART: Tinea capitis involves the scalp, and mainly occurs in children. It is uncommon after puberty.
Segment:7 7. Tinea Capitis.
DR. BART: The clinical presentation can vary from mild, and fine dandruff-like scales, with no hair loss, to heavier scaling with crusts and pustules, with hair loss.
DR. BART: Trichophyton tonsurans is a common cause of tinea capitis, particularly in African-American children. This is a very contagious infection spread by direct contact, combs, brushes and caps. It is sometimes called black dot tinea, because of the short stubs of broken off hairs, as demonstrated in Figure 3. Tinea capitis may also be associated with a kerion, which presents with erythematous, boggy and often draining painful nodules, as seen in Figure 4.
Segment:8 8. Tinea Corporis (Ring Worm).
DR. BART: Tinea corporis, often called ring worm, typically involves the trunk and extremities. When the face is involved, it is called tinea faciei. Depending on the fungus, this may be spread from human to human, or from animals such as dogs or cats to humans.
Segment:9 9. Tinea Corporis.
DR. BART: Tinea corporis starts as a red scaly papule that spreads outward leaving an annular plaque with peripheral scales and central clearing as demonstrated in this patient.
Segment:10 10. Tinea Manuum.
DR. BART: Tinea manuum is more common in men. It typically presents with a diffuse erythema and fine scaling over the palms, as seen in this patient. One or both palms may be affected.
Segment:11 11. Tinea Cruris (Jock Itch).
DR. BART: Tinea cruris mostly occurs in men and is rare in women and children. It usually involves the upper medial thighs, as seen in this patient.
DR. BART: It may also involve lower abdomen and buttocks, but is not usually seen on the scrotum or penis.
Segment:12 12. Tinea Pedis (Athlete's Foot).
DR. BART: Tinea pedis or athlete's foot is more commonly seen in men, and may be related to wearing occlusive shoes, or exposure from the showers, and swimming pools.
Segment:13 13. Tinea Pedis.
DR. BART: Interdigital involvement with scales or fissures is shown in Figure 8. Figure 9 shows a diffuse moccasin pattern over the soles.
DR. BART: Occasionally vesicles or bullae maybe seen. Fungal toenail infections are commonly seen in chronic infections.
Segment:14 14. Onychomycosis (Tinea Unguium).
DR. BART: Onychomycosis or tinea unguium most frequently affects the toenails, and accounts for 50% of all nail disease. The fingernails may also be affected. It presents as a thickened discolored nail plate with subungual hyperkeratosis or onycholysis, as seen in this patient.
Segment:15 15. Yeast Infections.
DR. BART: Common yeast infections of the skin include tinea versicolor and candida.
Segment:16 16. Tinea Versicolor.
DR. BART: Tinea versicolor is caused by Malassezia. It usually occurs in young adults, in warm and humid climates. It presents with fine, powdery, scaly macules on the trunk and arms, as shown in this patient. It may result in hypo- or hyperpigmentation.
Segment:17 17. Candidiasis.
DR. BART: Candida infections are mostly caused by Candida albicans, and are seen most commonly in infants, and in pregnant, elderly, and immunosuppressed individuals.
DR. BART: Body folds are usually affected, although it can be seen in the mouth causing thrush.
Segment:18 18. Candidiasis.
DR. BART: Candida infections present with a macerated erythematous plaque, with satellite papules shown in the diaper area of this patient.
Segment:19 19. Viral Infections.
DR. BART: I will now discuss four common viral infections affecting the skin.
Segment:20 20. Herpes Simplex.
DR. BART: Herpes simplex virus can cause primary, latent, and recurrent infections.
DR. BART: The primary infection tends to be much more severe. Recurrent infections are common, often in the same location as the primary, and tend to be less severe. Herpes simplex infections begin with erythema, which can be itchy or painful. Within one or two days, small grouped vesicles develop, which enlarge and become eroded after 4 to 5 days. The eruption clears in 7 to 10 days.
DR. BART: Herpes simplex virus one, usually affects the vermilion border of the lip, as seen in this patient, but may involve other areas of the face or within the mouth, and occasionally on the trunk or extremities. Herpes virus two usually affects the anal, genital, and buttock areas. The herpes simplex virus resides within the nerve tissue, and may be induced after skin irritation, sun exposure, and secondary to fever.
DR. BART: It may be much more severe and may spread extensively in patients with atopic dermatitis, or immunocompromised individuals.
Segment:21 21. Herpes Zoster.
DR. BART: Herpes zoster is caused by reactivation of latent varicella or chicken pox infections, in which the virus is residing in the nerve tissue. It develops in the distribution of the affected sensory nerve. Intense pain may develop in this area, usually at the time of the skin eruption, but may precede the eruption by one or a few days.
DR. BART: The eruption resolves after three to five weeks, but pain may persist for months to years, referred to as postherpetic neuralgia. Eruption and pain is more severe with advanced age and in immunocompromised individuals, in which the eruption may become disseminated secondary to viraemia.
Segment:22 22. Herpes Zoster.
DR. BART: Herpes zoster presents with grouped vesicles on an erythematous base.
DR. BART: The trunk is the most commonly affected area, as seen in this patient. The trigeminal nerve is affected in 10 to 15% of cases and may result in severe damage to the eye.
Segment:23 23. Molluscum Contagiosum.
DR. BART: Molluscum contagiosum is a common contagious DNA viral infection, which presents with dome-shaped pearly or pink papules, two to 10 millimeters in size. Often showing central umbilication, as shown in this patient.
DR. BART: The infection typically occurs in children on the face, trunk, and extremities. In adults, it is usually sexually transmitted, occurring in the anal, genital, suprapubic, and thigh areas.
Segment:24 24. Warts (Verrucae Vulgaris).
DR. BART: Warts or verrucae vulgaris are caused by the human papillomavirus, HPV, a DNA virus with over 100 genotypes. It is seen more frequently in children, young adults, and immunocompromised individuals.
DR. BART: Genotypes, such as 16, 18, 31 and 33, may be oncogenic, inducing malignant transformation to squamous cell carcinoma in the anogenital and oropharyngeal areas.
Segment:25 25. Warts on Hands and Feet.
DR. BART: The patient in Figure 16 demonstrates typical verrucous papules on the hand. Figure 17 shows closely set clusters of warts, referred to as mosaic warts. Sometimes brown dots can be seen within the warts caused by thrombosed capillaries.
Segment:26 26. Flat Warts and Genital Warts.
DR. BART: Flat warts, or verrucae planae, as seen in Figure 18, present as flat-topped papules, one to three millimeters in size. Condylomata accuminata also called genital or venereal warts present as smooth-surfaced exophytic papules, which may be skin-colored, brown or white, as seen on the penis in Figure 19. This infection is one of the most commonly sexually transmitted diseases.
Segment:27 27. Bacterial Infections.
DR. BART: Bacterial infections often affect the skin.
Segment:28 28. Impetigo.
DR. BART: Impetigo is most frequently caused by Staphylococcus aureus, but it may also be caused by group A hemolytic streptococci, including the nephritogenic strains. It presents with vesicles, which quickly erode and develop honey-colored crusting. This is often seen on the face, as demonstrated in this patient.
Segment:29 29. Boils.
DR. BART: Furuncle or boils are caused by infection with Staphylococcus aureus, which may be methicillin sensitive, or methicillin resistant. It presents as deep-seated, inflamed, tender, fluctuant cystic nodules, originating within a hair follicle, as seen in this patient.
Segment:30 30. Cellulitis.
DR. BART: Cellulitis is usually caused by Staphylococcus aureus, or group A Streptococcus.
DR. BART: Risk factors include trauma, fissured skin, vascular insufficiency, surgery, diabetes, and intravenous drug use. It presents as an acute onset of localized erythema with an advancing ill-defined border, as seen on the leg of this patient.
Segment:31 31. Syphilis.
DR. BART: Syphilis is a sexually transmitted disease caused by Treponema pallidum, a spirochetal bacterium. It is now most frequently seen in Black and Hispanic populations and in men who have sex with men.
DR. BART: The secondary form may mimic many other cutaneous disorders. Thus it is called "the great masquerader."
Segment:32 32. Primary and Secondary Syphilis.
DR. BART: The primary stage begins about three weeks after infection, presenting with a nontender, indurated, firm ulcer, with raised borders called a chancre, as demonstrated in Figure 23. The secondary stage begins four to 10 weeks after onset of the infection, and presents with macules and papules.
DR. BART: Typically on the trunk, as seen in Figure 24, and on the palms and soles. Shallow erosions may occur in the mouth and on the lips, and moist wart-like papules, condyloma lata may occur in the anogenital area.
Segment:33 33. Infestations and Bites.
DR. BART: Skin manifestations of arthropod infestations and bites are frequently seen.
Segment:34 34. Scabies.
DR. BART: Scabies is caused by a microscopic mite, Sarcoptes scabiei, and spread by direct person to person contact.
DR. BART: The adult female burrows into the skin, resulting in short, wavy lines, inflamed papules and vesicles, which are intensely pruritic, as seen on the wrist of this patient. It affects the hands, particularly the finger web areas, the ventral wrists, as well as the arms, trunk, and genitalia.
Segment:35 35. Lice (Pediculosis).
DR. BART: Pediculosis or lice infestation is caused by human lice, blood sucking, wingless insects.
DR. BART: On the scalp, head lice attach their eggs called nits, at the base of the hair, as seen in this patient. This is more frequently seen in children, and causes pruritus, erythematous, papules, and excoriations.
Segment:36 36. Body and Crab Lice Infestations.
DR. BART: Body lice live and deposit their nits in the clothing, particularly along seams, and manifest as severely pruritic papules and excoriations on the trunk and proximal extremities.
DR. BART: Crab lice as seen in this slide, live in the hairy areas of the pubic region, lower abdomen, and thighs. The nits are deposited at the base of the hairs. Severe pruritus and excoriations may result in pyoderma, and regional lymphadenopathy. Lice are spread primarily by person to person contact.
Segment:37 37. Lyme Disease.
DR. BART: Lyme disease is caused by Borrelia, a spirochete transmitted by the ixodes tick, as seen in Figure 28.
DR. BART: A great majority of cases occur in the Northeast U.S. and in Minnesota and Wisconsin. It begins with a papule which expands peripherally into an annular plaque, as seen on the trunk of patient in Figure 29. Multiple skin lesions may then develop. The organism may infect multiple organ systems, and can cause significant morbidity and death.
Segment:38 38. Bed Bugs.
DR. BART: Bed bugs, Cimex lectularius are blood sucking, wingless insects, shown in Figure 30.
DR. BART: They feed on humans at night. The bites present as very pruritic urticarial papules, and sometimes bullae. Often in clusters of three or four bites, as seen on the back of the patient in Figure 31. They live in protected areas such as in and around mattresses, behind picture frames and wallpaper, and in cracks on the floor.
DR. BART: They can be found at nighttime in the bedding, but can be very elusive and difficult to eradicate.
Segment:39 39. Summary.
DR. BART: In summary, cutaneous infections and infestations may have various clinical manifestations on the skin. It is important to confirm the diagnosis with scrapings, cultures, skin biopsy, and in the case of Lyme disease and syphilis, with serologic examinations.
Segment:40 40. Contributors.