**5. Infestations of scalp**

### **5.1. Pediculosis capitis**

Pediculosis capitis [PC] [head lice] is a major worldwide infestation caused by *Pediculus humanus capitis* seen in school-aged children of 3–12 years of age. The prevalence of PC is usually higher in girls and women and varies greatly from country to country. It is 0.7–59% in Turkey, 0.48–22.4% in Europe, 37.4% in England, 13% in Australia, up to 58.9% in Africa and 3.6–61.4% in the Americas [67]. There are estimates that 6–12 million children in the United States are infected with PC annually [68]. The prevalence in 5318 elementary school children, aged 8–16 years in Mersin, Turkey, was 6.8% [69]. In another study of 1569 school children, aged 7–14 years, the prevalence of head lice was 16.6% [70]. It tends to be more prevalent in children because they have a high incidence of head-to-head contact with other children. Girls were at a greater risk for head lice because of their tendency to have longer hair than boys and social behaviour [close contact].

The lice are spread by direct head-to-head contact as well as by the sharing of clothing, headgear, hats, combs, hairbrushes, hair barrettes and pillows. PC affects all socioeconomic classes. Although direct contact with an infested individual can cause PC, personal and environmental hygiene are not risk factors for PC [71].

The head louse [plural-lice] is an ectoparasite whose only host is humans for survival. There are three stages that comprise the life cycle of the louse: egg, nymp and adult. Adult female louse lays their eggs [nits] on hair shafts. The nits are usually laid close to scalp for warmth, because they must stay warm in order to hatch. These nits cannot be moved along the hair shaft in contrast to pseudonits. Only in warmer climates, nits can be found 15 cm or more from the scalp, especially favour the nape of the neck. They are of size 0.8 mm × 0.3 mm, oval and usually yellow to white and are located 6 mm from scalp. Nits take about 1 week to hatch [range 6–9 days]. The nit hatches and release a single nymph. Nymph becomes an adult after three molts, about 7–10 days after hatching. Each instar molts every 3–4 days, and after the third molt, it becomes adult louse (**Figure 6**). The first and second instar or nymph forms are relatively immobile. Mobile forms are the third instar forms and adults form. The mature adult louse is approximately the size of a sesame seed [2–3 mm] and is tan to greyish-white [68, 72, 73]. Female lice are larger than males and must take blood before copulation. After copulation she lays between 5 and 10 eggs a day. The adult males usually do not survive after copulation. The adult louse lives only up to 36 hours away from its host. Head lice can travel up to 23 cm/min by crawling. The head lice do not attach firmly to smooth surfaces [e.g., glass, metal, plastic, synthetic leathers] [72, 74].

**Figure 6.** Schematic representation of life cycle of head louse.

According to the patterns of McCarthy made in 1940, secondary SA is classified into two types: symptomatic SA and essential SA. The other cutaneous manifestations of syphilis is not seen in essential SA. Essential SA, characterised by alopecia without any other visible syphilitic lesions on the scalp, may appear as one of three different clinical patterns: 'motheaten' alopecia, diffuse alopecia and mixed pattern of alopecia [58, 60]. The 'moth-eaten' pattern alopecia [alopecia syphilitica] is considered the most common and characteristic form of

The diagnosis of SA is confirmed by both patient's sexual history and positive serological tests for RPR and TPPA. The histopathology findings of SA usually include a normal epidermis with areas of follicular hyperkeratosis. While the number of anagen follicles are reduced markedly, the number of catagen and telogen follicles increase. A perivascular and perifollicular [especially in the peribulbar region] lymphocytic dermal infiltration with scattered

The differential diagnosis of 'moth-eaten' alopecia includes alopecia areata, trichotillomania and tinea capitis except from syphilis [64]. Under trichoscopy black dots, focal atrichia, hypopigmentation of hair shaft and yellow dots are observed in the hair loss region. Alopecia areata, tinea capitis and trichotillomania differ from SA with absence of exclamation hair,

The antisyphilitic treatment with a weekly dose of 2.4 million units of benzathine penicillin for 3 weeks or procaine penicillin 600,000 units i.m. daily for 10 days leads to complete resolution of alopecia. Hair growth is observed about 6–12 weeks after the start of the treatment [57, 65, 66].

Pediculosis capitis [PC] [head lice] is a major worldwide infestation caused by *Pediculus humanus capitis* seen in school-aged children of 3–12 years of age. The prevalence of PC is usually higher in girls and women and varies greatly from country to country. It is 0.7–59% in Turkey, 0.48–22.4% in Europe, 37.4% in England, 13% in Australia, up to 58.9% in Africa and 3.6–61.4% in the Americas [67]. There are estimates that 6–12 million children in the United States are infected with PC annually [68]. The prevalence in 5318 elementary school children, aged 8–16 years in Mersin, Turkey, was 6.8% [69]. In another study of 1569 school children, aged 7–14 years, the prevalence of head lice was 16.6% [70]. It tends to be more prevalent in children because they have a high incidence of head-to-head contact with other children. Girls were at a greater risk for head lice because of their tendency to have longer hair than boys and social

The lice are spread by direct head-to-head contact as well as by the sharing of clothing, headgear, hats, combs, hairbrushes, hair barrettes and pillows. PC affects all socioeconomic classes. Although direct contact with an infested individual can cause PC, personal and environmen-

secondary syphilis [61, 62].

208 Hair and Scalp Disorders

**5. Infestations of scalp**

**5.1. Pediculosis capitis**

behaviour [close contact].

tal hygiene are not risk factors for PC [71].

plasma cells is observed in some cases [63].

coma hair, flame hairs or v-sign, respectively [57].

The head louse takes a blood meal [hematophagia] usually 4–5 times per day. Chronic and heavy lice infestation can rarely lead to anaemia, especially in females. Pruritus is the most common complaint and is believed to be the result of a hypersensitivity reaction to the saliva of lice. On examination, nits are seen that firmly attached to hair shaft within 6 mm from the scalp skin especially in the occipital pit [louse pit] and retro-auricular areas. Scratches on the skin may lead to secondary bacterial infection and impetiginisation. Serous purulent discharge may result in the formation of a plica [plica polonica or plica neuropathica]. There are innumerable nits and live lice in patients with plica polonica. Cervical lymphadenopathy and conjunctivitis may also be seen. Lice infestation can cause allergic reactions within the nasal cavity manifested by nasal obstruction and rhinorrhea [72, 74, 75].

The diagnosis of head lice infestation is made through finding viable eggs [nits], nymphs and live adult lice. For the diagnosis, the use of a louse comb is more efficient than direct visual examination of the scalp [76]. Examining suggestive particles under the microscope may be helpful to confirm the diagnosis. Non-contact dermoscopy is also a useful instrument for differentiate nymph-containing eggs from empty cases or pseudonits [72]. Histology is rarely required for diagnosis. Examination of a louse bite reveals intradermal haemorrhage and a deep, wedge-shaped infiltrate with many eosinophils and lymphocytes.

Differential diagnosis of head lice includes seborrheic scales, hair casts [inner root sheath remnants], pityriasis amiantacea, white piedra, black piedra, impetigo, pili torti and monilethrix. It should kept in mind that, in contrast to nits, hair casts are freely movable along hair shaft [72].

Basically, therapeutic wet combing, topical application of a pediculicide and oral treatment [Trimethoprim-sulfamethoxazole and ivermectin] are used to eliminate head lice. Wet combing is a mechanical removal of the lice. The patients must comb their wet hair with a fine-toothed comb every 3–4 days for a total of 2 weeks. If all young lice are combed out a few days after hatching, the infestation can be eradicated completely. Pediculicides are the most effective treatment for head lice. They can be divided into three types. Pediculisides with neurotoxic mode of action are permetrin [Nix®], pyrethrin [Rid®], malathion [Ovide®], carbaryl, lindan [Kwell®] and spinosad [Natroba®]. Dimeticones [Nyda®, Hedrin®], isopropyl myristate [Resultz®] and 1,2-octanediol are the pediculicides with physical mode of action. The other group of pediculicides is plant-based pediculicides. All topical preparations are used for two or three applications, 1 week apart [68, 71].

Because permetrin and pyretrin are non-ovicidal, they should be reapplied on days 7 and 13–15. Permethrin 1% is a synthetic pyrethroid and is approved for use in children aged 2 months or older. It shows neurotoxic effect by inhibiting the sodium ion flux through nerve cell membrane channels [68]. It should be applied on damp unconditioned hair for 10 min and then rinsed off. Pruritus, erythema and edema are its usual side effects [77]. Pyretrin is used for children aged 2 years and older. Malathion is a cholinesterase inhibitor. It is approved for use in individuals aged 6 years or older. Both malathion and lindan are ovicidal. Spinosad is ovicidal, killing both eggs and lice and also kills permethrin-resistant populations of lice. It is approved in patients aged 4 years and older [78]. Oral ivermectin is administered a single dose of 200 μg/kg and repeated in 10 days. It is restricted to children older than 5 years and weighing at least 15 kg [71].

Resistance of lice to the pediculocides is an important problem. Spinosad, benzyl alcohol 5% or malathion 0.5% may also be used, in case of resistance, for those older than 6 and 24 months, respectively. Another treatment option is manual removal of nits [especially the ones within 1 cm of the scalp]. It is recommended after treatment with any product. Besides these treatments, occlusive agents such as petroleum jelly, vinegar, isopropyl alcohol, olive oil, mayonnaise and melted butter can been used once per week for 3 weeks to suffocate the lice [68, 78].

Patients with head lice should have laundered potential fomites [e.g., towels, pillowcases, sheets, hats, toys] with hot water [at least 130°F/55°C] and then dried in a dryer using the hottest cycle. For items that are not machine washable, dry-cleaning may be an effective alternative or storing for 2 weeks in a plastic bag. Children should also be educated not to share combs, brushes, hair accessories and towels and to avoid head-to-head contact [72, 73, 78].
