Dermatology Lecture 9: Parasitic Skin Diseases 2022-2023

# Dermatology ## Lecture 9: Parasitic Skin Diseases ### 2022-2023 By Msaeed & Dr Mohamed saeed # Parasitic Skin Diseases ## Scabies Scabies is a contagious disease caused by a mite. The female Sarcoptes scabiei ; which invade the epidermis and form a burrow. **Def:** * The female Sarcoptes...

# Dermatology ## Lecture 9: Parasitic Skin Diseases ### 2022-2023 By Msaeed & Dr Mohamed saeed # Parasitic Skin Diseases ## Scabies Scabies is a contagious disease caused by a mite. The female Sarcoptes scabiei ; which invade the epidermis and form a burrow. **Def:** * The female Sarcoptes scabiei ; which invade the epidermis and form a burrow **Mode of infection** * **Direct:** Close personal contact with infected patient (sexual or nonsexual). * **Indirect:** infection through fomites as towels, cloths, or beds (especially in severe and/or crusted cases). **I.P:** 2 weeks- 2 months. * The **pathognomonic** lesions of scabies are the burrows which may be present in a few or large numbers. * The lesion: * At the end of the burrow a vesicle or papule is usually seen. * Burrows are seen early in infection. * Later on, repeated itching removes the roof of the burrows, and it may be difficult to find any. * **Severe itching** It is worse at night. * **Allergic sensitivity** to the mite or its products is the cause of itching & development of lesions other than burrows. **Clinical picture:** > Other lesions that are seen in scabies include: > > * Small urticarial papules, scratch marks. > * Eczematous plaques which is prominent on the breast of women. > * Secondary infection as pustules, boils, and impetigo. > * Vesicles may occur independently of burrows especially at the sides of fingers. > * Bullae may be seen in infants particularly on palms & soles. **Distribution** of lesions is very characteristic usually the delicate parts of the skin: * Usually generalized & symmetrical. * The sites affected are: * The finger webs, anterior aspects of the wrists * Ulnar border of hand & forearms * Elbows, axillae * Around the nipples in women * Abdomen, periumbilical region * Male genitalia, natal cleft, lower parts of buttocks, * Medial aspects of thighs, legs, around ankles & dorsa of feet. * Face & interscapular region are usually free. ## Clinical types **Human classic scabies** described above. **The differences from human scabies are:** * **Shorter I.P.** * **Self-limiting** after eliminating the source of infection. * **Sites:** localized or generalized according to the mode of exposure. * Webs & genitalia are free. * **Lesions:** papules, wheals or papulovesicles with **absence** of burrows. * It is **not transmitted** from human to human. **Animal scabies** **Scabies in infants and young children** * has **Atypical distribution** of lesions with involvement of scalp, face, neck, palms and soles. **Nodular scabies** * persistent reddish brown pruritic nodules may occur after treatment of scabies. * The sites of predilection are axillae, male genitalia, groins, umbilicus or anywhere. * These nodules represent **hypersensitivity** reaction to mites. **Scabies incognito** * The lesions and the course are modified by the application of topical or systemic steroids. * Scabies has **unusual extent** and distribution. * This type represents an abnormal host immune response to the mite. * The condition is seen in the following groups. * Mentally retarded. * Patients with poor cutaneous sensation * Patients with **severe systematic diseases** like leukemia and DM. **Crusted (Norwegian)scabies** * Clinically Norwegian scabies is characterized by: * large crusts on the hands and feet with subungual hyperkeratosis. * Erythematous scaly plaques occur on the face, neck, scalp and trunk and may become generalized. * Itching may be absent * The number of the invading mites may reach up to 2 millions, so these patients are **highly contagious** and may initiate epidemics of scabies. **Difficulty** to see the burrows due to **frequent bathing**. * Like classic scabies * but lesion is more **common in the area with contact with bed** * Like classic scabies but MOT maybe **sexually transmitted** (In this case u must search for other venereal diseases) ## Complications: * **Bacterial infections**, e.g., impetigo, cellulitis, lymphangitis, boils and folliculitis . * **Eczema** may follow scratching or application of topical scabicides. * **Acarophobia:** * After successful treatment * The patient continues to itch and believes that he still has scabies * Such patient usually has **psychological disorder**. ## Diagnostic criteria: * **Marked itching** worse by night. * Infection of **more than one member** of the family. * **Classical distribution.** * **Polymorphic eruption.** * Demonstration of the mite under microscope: * burrow is moistened with KOH 20% and scraped with a blunt scalpel. * The scraping is examined under microscope for mites, eggs and/or fecal pellets. * **Dermoscopy** can prove useful for direct in vivo visualization of mites and eggs. **D.D.:** * Popular urticaria * Eczema * Erythema multiform ## Treatment: **General measures:** * Boiling of cloths, bed linens, towels. * The mites cannot survive at temperature about 50°C for longer than 5min. * It cannot survive at room temperature in blanket or clothing for more than 2w * Treatment of all members of the family except in animal scabies. * Treatment of infested animals. * are applied to the entire trunk and extremities | Drug | Application | Pros & cons | |---|---|---| | **Permethrin 5%** | Applied for 2 successive nights, then washed 24 hours after the second application | **Pros** It is safe in infants and pregnant women | | **Crotamiton 10%** | applied for 2 successive nights, then washed 24 hours after the second application. | --- | | **Benzyl benzoate 25%** | for 2 successive nights | --- | | **Sulphur:** 10% in adults, 3-5% in infants and children | It is applied every night for 4 successive nights. | **Pros** However, it is safe in infants, children, and pregnant women. **Cons** It is less acceptable because of odour, messiness, staining | | **Gamma benzene hexachloride 1%** | one application is left for 12 hours | **Cons** not used in infants, young children, pregnant or lactating women and in patient with seizures| | **Malathion 0.5%** | Applied for 12 h then washed | --- | | **Ivermectin 1% solution** | applied for 12 hours then washed with a second application after a week. | --- | **Topical Scabicides** (cont) **NB:** In pregnant women * The drug of choice is permethrin, with malathion as an alternative. * It is suggested that topical agents should be removed from the nipples before breast feeding, and then reapplied. **Systemic:** * **Oral Ivermectin** * Very effective antiscabetic drug.- 6 mg tablets. * Dose: 6mg/15kgm single dose (0.2-0.4 mg/kg) ; repeated after one or 2weeks. * It is extremely safe, but is not recommended for children who weigh <15 kg, pregnant women and breastfeeding mothers * Antihistamine for itching. * Antibiotic for bacterial infections. ## Treatment of nodular scabies: * Intralesional injection of steroid * Surgical excision. ## Causes of persistent itching after treatment of scabies: * Persistence of hypersensitivity state which will spontaneously subside. * Unsuccessful treatment t. * Irritation of the skin by the antiscabetic topical drugs. * Nodular scabies. * Acarophobia. * Reinfection. # Pediculosis * **Capitis** * **Corporis** * **Pubis** ## Pediculosis capitis **Def:** * Pediculosis is caused by **lice** which are small gray-brown, blood sucking parasites * Each female lays many eggs which appear as **white nits** firmly attached (cemented) to the hair shaft * Each nit hatches within a **week.** **Site:** * Pediculosis Capitis occurs on the hair of the scalp, mainly above the ears and occiput. * Beard and moustache may be infested. **MOI:** * Pediculosis capitis is communicated by **direct contact**, sharing hats, combs & brushes. **Clinical picture:** * **Epidemiology:** Although the disease is more common in children, it may occur in adults * **There is itching** of the scalp * This causes **scratching with impetigo** and **cervical lymphadenopathy.** * The general health may be impaired from **septic absorption.** **TTT** * **Cutting the hair short** and **systemic antibiotic** if there is impetigo. * Co-trimoxazole is the preferred antibacterial because it also has pediculicide effect. * **Pediculicides** are given after control of bacterial infection. * **Topical pediculicide lotion:** Malathion 0.5%, Ivermectin 1%, or Permethrin 5%.,G:B:H1% * It is applied to the dry clean hair for 12 hours then washed. * Any medication must be repeated after one week (to kill the residual nits and to overcome resistance). * **Oral Ivermectin:** 0.2-0.4 mg/kg single dose that must be repeated after 8 d. * **Removal of nits** * is done by application of **white vinegar** diluted with equal amount of water, * Vinegar will dissolve the cement substance that attaches the nits to the hair shaft. → Washing is done after 1 - 2 hours and comb the hair with fine-toothed comb to remove the nits. ## Pediculosis pubis (Crab lice, Pthirus pubis) **Def:** * The pubic louse is **sexually transmitted** and is mostly found in young adults. * Pubic lice infest the **pubic** and **perineal hair** * It may also infect the **eye lashes** **Site:** * Crab lice cause **severe itching** in the pubic region with 2ry eczema and infection. **Lesion:** * The lice **firmly adhere** to the base of hairs * they can be skin-coloured or mimic **haemorrhagic crusts.** # Urticaria * Urticaria is an acute skin disorder characterized by formation of **wheals** MCQ * It may be allergic or **non-allergic**. * **Liberation of histamine** and or other substances from the mast cells may result * from Allergic Reaction nearby the mast cells * from Non-Allergic Reaction, i.e., direct action of certain stimuli on mast cells. ## Causes: * **Foods** (fish, egg, strawberries) **Food additives** (e.g., yellow azo dye and benzoate) * **Drugs** e.g., Aspirin, morphine, sulpha, penicillin, blood and blood products. * **Infections:** e.g. * **Bacterial:** tonsillitis, sinusitis, cystitis, prostatitis, cholecystitis, dental abscess. * **Viral:** hepatitis B. * **Fungal:** dermatophytosis, candidiasis. * **Parasitic:** ascaris. * **Protozoal:** trichomonas. * **Inhalants:** dust, pollen, perfumes, feather, tobacco. * **Collagen diseases** e.g., SLE, dermatomyositis and rheumatoid arthritis. * **Neoplasms:** lymphoma, leukaemia & internal malignancy. * **General diseases:** thyrotoxicosis, uraemia, liver diseases, polycythaemia vera. * **Physical factors:** sun, cold, water, heat. * **Psychogenic causes:** emotional stress, anxiety. * **Unknown:** 50% of acute urticaria are idiopathic and about 90% of chronic urticaria are either idiopathic or autoimmune due to histamine releasing autoantibodies. ## Clinical picture: * **Common skin disease** characterized by sudden appearance of itchy wheals that last from few hours up to 48 hours, then fade away (evanescent) and new lesions may appear, a feature distinguishing urticaria from other urticarial like lesions of the skin. * The wheals appear as **erythematous papules, plaques and or streaks.** * The lesions may be **localized or generalized.** * The size is variable from **pinpoint to many inches across.** * The shape of the lesion may be **bizarre, geographic & or annular.** ## Association: * **Angioedema** (diffuse swelling in certain areas of thin skin & loose SC tissue such as eye lids, lips, genitalia) may occur with wheals. * **General symptoms** may indicate involvement of **internal organs** such as * GIT (nausea, vomiting, dysphagia) * respiratory tract (hoarseness, wheezing and dyspnea). ## Course: * **acute urticaria:** the lesions usually disappear within a few hours or days * **chronic urticaria:** the disease persists for more than 6 weeks * **Spontaneous improvement** may occur even in absence of diagnosis or treatment. ## Special types of urticaria: * Angioedema * Dermographism * Cold urticaria * Aquagenic urticaria * Cholinergic * Solar urticaria * Contact urticaria * Serum sickness ## Treatment: * **careful search for the cause and its removal if possible is essential.** * **Antihistamines:** specific treatment * **Systemic steroids:** adjuvant treatment in severe cases resistant to other treatments. * **Adrenaline** * **Ca gluconate** * **Local soothing lotion**, as calamine lotion # Papular Urticaria (Prurigo simplex) **Def:** * **Hypersensitivity** to insect bites such as fleas and mosquitoes. **Clinical picture:** * **Occurs** in infants and children. * **Lesions:** * itchy small red papules 1-5mm. * arise on top of wheals or independently on normal skin. * Vesicles are also rarely seen. * Due to itching the papule becomes excoriated and secondary infection may occur. * **Sites:** * The eruption occurs mainly on the limbs. * The trunk may show few lesions. **Course:** * It is frequently seen in children moving to new areas where mosquitoes prevail. **Resolution** * It usually **subsides spontaneously,** * **even** when exposure to mosquitoes continues. * This **probably results** from a process of **gradual desensitization** to the antigens of mosquitoes. **Maybe** * **Prurigo of Herba (atopic)** * It may **persist indefinitely** with remission & exacerbation in atopic individuals in whom the lesions are numerous & the skin is **lichenified**. * Superficial lymphadenopathy especially of the inguinal and axillary glands is usually present. * The association of * itching, lichenified skin, * excoriated shotty papules * superficial lymphadenopathy * is known as prurigo of Hebra. # Atopic dermatitis: * **4 major criteria:** * Pruritis * Typical morphology and distribution for age group * Chronic or chronically relapsing dermatitis * Personal or family history of atopy ## Treatment: * **General** * Disinfestations. * Change of environment * **Drugs** * Oral antihistamines. * Short course of systemic steroids in extensive cases. * Local soothing lotion or topical steroids. ## Case scenario * A 31 y-old man is complaining of itching that is worse by night of 3 weeks duration. 2 days ago his wife also started to scratch her skin especially during sleep. * **Q1:** What are the classic sites you must examine to search for skin lesions? * **Q2:** enumerate the types of lesions you expect to find. * **Q3:** What is the most probable diagnosis? ## Answers * **Q1:** The webs of fingers, flexure aspects of wrist joints, antecubital fossae, axillae, around the umbilicus, groins, buttocks, medial aspects of thighs and dorsae of feets. * **Q2:** Polymorphic eruption: papules, scratch marks, excoriated papules, impetigo lesions (superficial bacterial infection) in the form of pustules and crusted lesions. * **Q3:** Diagnosis is scabies. ## Questions 58 1. Scabies in infancy can be treated by: * Permethrin 2.5-5%... * Gamma benzene hexachloride 1%. * Benzoyl benzoate 25% * Malathion 0.5% * Ivermectin tablet. 2. Primary lesion of scabies is * Plaque. * Burrow. * Nodule * Papule. * Macule 3. Papular urticaria is caused by: * Drugs * by Emotional stress. * Cold weather. * Insect bites * Liver disease **Ans:** 1-a, 2-b, 3-d