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Ростовский Государственный Медицинский Университет

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Fig. 69.2 Net-like erythema ab igne lesions appearing on skin exposed to heat for a long time or repeatedly

69 Erythema Ab Igne

permanent hyperpigmentation occurs. In cases of hyperpigmentation, skin emollients and a combination cream of 5% hydroquinone, 0.1% retinoic acid, and 0.1% dexamethasone can sometimes be helpful, and whitening management including laser toning using the a Q-switched Nd:YAG laser is helpful. There are reports that the application of 5-FU cream is effective for lesions showing dysplasia. After listening to the detailed explanation, Ms. K leaves the treatment room, saying that she needs to remove the heater immediately (Figs.69.11 and 69.12).

Figs. 69.3 and 69.4 Erythema ab igne observed on the abdomen

Figs. 69.5 and 69.6 Erythema ab igne on the leg

69 Erythema Ab Igne

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Fig. 69.7 Erythema ab igne on the back

Figs. 69.9 and 69.10 Net-like hyperpigmentation observed in erythema ab igne

Fig. 69.8 Erythema ab igne and low-temperature burn

Figs. 69.11 and 69.12 No longer being exposed to heat, and after 5 treatments at 1-week intervals with a Q-switched Nd:YAG laser

Scabies, Scabies Mites, Scabies Mite

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Burrows

Find the scabies mites hiding in the child’s skin!

Among the patients who come to our hospital through referrals or internet information, especially those who register as a family unit, when Teacher Kim hands me gloves, I intuitively know, “Ah! They’ve come for a scabies diagnosis!” Usually, diagnosis is made by dropping oil and scraping with a scalpel for microscopic examination or applying ink to nd scabies mite burrows, but I magnify the suspicious area 200 times and directly check for scabies mites and mite burrows with my own eyes. This method (Jeong’s method), which is not even in dermatology textbooks, allows for diagnosis in just a few seconds and it’s a really convenient conrmation method as the existence of scabies burrows and mites can be conrmed live through a monitor (Fig.70.1).

Scabies is a highly contagious skin disease caused by scabies mites parasitizing the skin, causing severe itching that makes it difcult to sleep at night, not only making life uncomfortable but also potentially spreading to everyone living together, posing a public health threat. Especially in vulnerable patients such as children or the elderly, it can cause secondary infections, so its prevention and treatment are very important. Transmission occurs through direct skin-to-

Fig. 70.1 200× magnied photo of a scabies mite burrow

skin contact, including sexual contact, and rarely, it can also occur through contact with heavily infested fomites such as clothing and towels. The human scabies mite (Sarcoptes sca- biei var. hominis) is an absolute parasite of humans, with humans as the primary host, and it has spread gradually to wild animals through livestock. Scabies mites have over 40 species of animals as hosts, and the species reported in Korea are the human scabies mite (Sarcoptes scabiei var. hominis), canine scabies mite (Sarcoptes scabiei var. canis), porcine scabies mite (Sarcoptes scabiei var. suis) of three species, human scabies mite is commonly notated to as Sarcoptes scabiei .

The human scabies mite burrows into the human epidermis, where the female lays eggs that hatch and mature into adults in about 2 weeks. The life cycle is egg → larva → nymph stages → adult, with the larva having six legs and the nymph and adult having eight. It becomes an adult after one (male) or two (female) nymph stages. The eggs are oval and

0.10–0.15 mm in size, and the female can survive for 4–6weeks, laying an average of 40–50 eggs. The eggs differentiate into larvae after 3–5days, and the larvae move to the skin surface and dig almost invisible burrows, which are called molting pouches and are different from the scabies mite burrows made by adults. The larvae become adults after going through the nymph stage for 10–14days, and the adult female moves to the skin surface after mating with a male in the molting pouch, makes a scabies mite burrow in the stratum corneum, and lays 2–3 eggs a day. The male dies within 2days after mating, so the ratio of females to males is about 10:1 (Figs.70.2, 70.3, 70.4 and 70.5).

Scabies is classied into classical scabies, crusted scabies (Norwegian scabies), nodular scabies, scabies incognito, canine scabies, etc., depending on the number of burrows caused by scabies mites, the presence or absence of scaly lesions, the presence or absence of nodular lesions, and the species of the causative scabies mite. In particular, crusted scabies, canine scabies, nodular scabies, scabies incognito, scabies in infants or the elderly, scabies in AIDS patients,

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70 Scabies, Scabies Mites, Scabies Mite Burrows

and scabies in patients living in clean environments show unique clinical features different from classical scabies.

The diagnosis of scabies can be made by observing small punctate lesions scattered in the affected area, characteristic nocturnal itching, the discovery of scabies mite burrows, nodular lesions on the male genitalia, and family history. It can be conrmed by identifying a scabies mite, its eggs, or feces pellets (scybala) using a microscope, dermatoscope, or high-magnication imaging device. In particular, severe itching in the ngers, perianal area, and genitals is helpful in diagnosis.

The presence of very small tunnels, papules, or vesicles due to larvae or nymphs necessitates careful observation using a magnifying device. It is particularly important to look for mite burrows on the palms of the hands and soles of the feet in infants, children, or elderly patients. However, in cases of Norwegian scabies or scabies incognito, itching

Fig. 70.2 Scabies mite burrow found on the sole of an 8-month-old baby

may be mild or absent, and burrows are not found in canine scabies. Dropping India ink or gentian violet solution on a suspected mite burrow and wiping it off with alcohol after a while can help in diagnosis as the ink or GV seeps into the burrow and stains it darker than the surrounding area. The mineral oil method proposed by Muller etal. involves dropping a drop of mineral oil on a mite burrow, scraping it 6–7 times in the direction of the burrow with a scalpel, collecting the mineral oil containing corneocytes fragments, placing it on a slide glass, covering it with a cover glass, and observing it under a light microscope. When scraping the skin with a scalpel, it is best to do it with enough force to mix a little red blood cell. This mineral oil method is a convenient test for nding mites, as the viscosity of the mineral oil allows all the contents of the burrow to be collected without loss, and it can detect living mites and oval brown scybala of 20–30μm size that can help in diagnosis. If there is no mineral oil, glycerin or cedar oil used for high-magnication observation under a microscope can also be used. Clinically, observing mites under a light microscope through the skin scraping technique using mineral oil is an essential test for the diagnosis of scabies, but there are many cases where it is difcult to observe depending on the specic situation, such as atypical lesions or nodular scabies (Fig.70.6).

Recently, dermoscopy, commonly used for differential diagnosis of pigmented skin diseases, is being used for the diagnosis of scabies. By conrming the triangular shape of the front part of the mite showing brown deposition in the skin (“hang glider sign”) or the triangular jet structure representing the mouth part and two pairs of front legs of the mite and the jet and ight cloud shape formed by the burrow made of air bubbles and excreta (“jet with condensation trails”), the positive rate of the skin scraping test can be increased. Dermoscopy is considered a useful test method with signicance in the diagnostic means of scabies or setting the site of

Figs. 70.3 and 70.4 Scabies mite burrows observable to the naked eye on an infant’s hands and feet

70 Scabies, Scabies Mites, Scabies Mite Burrows

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Fig. 70.5 Nodular scabies in an Infant

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Fig. 70.7 Diagnosis of mites using a dermatoscope

Fig. 70.6 Scabies mite burrow observed on the hand

the scraping test, especially in the elderly, immunocompromised, cases with unclear clinical symptoms, or infants who are difcult to cooperate with the skin scraping test. However, this test method is inuenced by the prociency of the performer, so even if evidence of scabies cannot be found in the test, scabies infestation cannot be completely ruled out. In addition, using a 3–7× magnifying glass in the clinic or using a digital magnication imaging device to magnify 10×, 30×, 60×, 200×, or 500× to nd scabies mite burrows is also helpful in diagnosis (Figs.70.7, 70.8, 70.9, 70.10, 70.11–70.14,

70.15, 70.16, 70.17, 70.18, 70.19, 70.20, 70.21–70.89,

70.90–70.92, 70.93, 70.94, 70.95, 70.96, 70.97, 70.98, 70.99,

70.100, 70.101, 70.102, 70.103, 70.104, 70.105 and 70.106).

Fig. 70.8 Diagnosis using a digital magnication device that magnies 10 times, 30 times, 60 times, 200 times, 500 times

However, in cases where it is not easy to diagnose because characteristic symptoms and lesions of scabies, such as vesicular scabies, do not appear together, diagnosis is often possible through histological examination. Scabies mite can be observed in the stratum corneum pathologically, and the gnathosoma is usually in contact with the upper part of the granular layer. Hyperkeratosis and localized spongiosis, and inltration of neutrophils and eosinophils within intercellular edema can also be found, and inltration of lymphocytes, histiocytes, eosinophils, and neutrophils can be observed around the vessels of the dermis. In Norwegian scabies, all stages of mite development can be seen in the tunnels formed layer by layer like a honeycomb inside the thickened stratum corneum due to hyperkeratosis. In elderly care facilities, it can be transmitted through caregivers, staff, visitors, etc., so it is necessary to strictly observe hygiene rules such as wearing gloves and washing hands before and after patient contact. In elderly patients, typical lesions showing mite burrows on ngers or between ngers are rare, and there are many cases showing atypical clinical symptoms such as papular dermatitis or eczematous lesions, so it is easy to fail in initial diagnosis.

Recently, much research has been conducted on scabies mite antigens that react with antibodies in the serum of laboratory animals infested with scabies mites. Some of them show homology to the house dust mite Dermatophagoides pteronyssinus, and research on scabies mite antigens and

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Figs. 70.9 and 70.10 Scabies mite burrow—10 times magnied image

70 Scabies, Scabies Mites, Scabies Mite Burrows

Figs. 70.11–70.14 Scabies mite burrow—60 times magnied image

genes is being conducted with the goal of not only diagnosing scabies but also immunotherapy. However, there is still no standardized laboratory test that can be used for mite diagnosis. Several candidate antigens and antibody immunoassays have been evaluated, but they are not optimal, and none has been widely adopted yet. Rapid tests with high sensitivity and specicity are urgently needed in this eld, and

the molecular biological tests should be a top priority in the scabies research agenda as they will provide a solution. A conventional polymerase chain reaction (PCR) test targeting the mitochondrial cytochrome c oxidase subunit 1 (cox1) gene of S. scabiei has been previously used for the diagnosis of scabies infestation, but the positive diagnosis rate was too low. Therefore, satisfactory results were not obtained.

70 Scabies, Scabies Mites, Scabies Mite Burrows

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Figs. 70.15 and 70.16 Scabies mite burrow—200 times magnied image

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Figs. 70.17 and 70.18 Scabies mite burrow—200 times magnied image

Figs. 70.19 and 70.20 Scabies mite burrow—200 times magnied image

Recently, Hahm etal. reported that the use of nested PCR based on the cox1 gene provides improved sensitivity in mite diagnosis. In this study, all cases proven by microscopy showed positive results in PCR tests and also showed an

improvement in detection rate by showing positive in 26% of those who showed negative under the microscope. It is thought that applying such new molecular biological techniques to mite diagnosis will be of great help in various clini-