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TREATMENT OF PLANTAR WARTS

By Dr Karen Stapleton, Edited by Dr Victoria Clayton.

These are classified clinically as either deep or superficial.Deep plantar warts (myrmecia) are usually painful and may be erythematous and oedematous. Superficial warts may coalesce into larger plaques called mosaic warts.

Paring with a size 15-scalpel blade helps differentiate plantar warts 1 from calluses and corns.Plantar warts have a peripheral rim of thickened skin, disruption of skin lines (dermatoglyphics) and characteristic red or black dots of thrombosed capillaries. Calluses have smooth surfaces and intact skin lines. Corns are hyperkeratotic conical shaped spikes projecting inwards. Direct pressure over these is extremely painful.

Preventive measures

As skin macerated by sweat is associated with less spontaneous resolution of plantar warts, it is important to control sweating by wearing open shoes, avoiding joggers and using cotton socks. Warts should be covered with waterproof tape in wet environments such as showers and swimming pools to avoid autoinoculation or infection of others.

First-line treatment of plantar warts

As with all warts, treatment choice is affected by the patient's age, pain tolerance, treatment preference and physician preference.

Liquid nitrogen cryotherapy with a hand-held spray unit

This is a painful procedure, not usually tolerated by children. A 30 second freeze is usually given. Sometimes a double-freeze thaw cycle is used, whereby the wart is frozen for another 30 seconds after it has been allowed to thaw.

While increasing the cure rate, this causes increased pain and blistering. After treatment, the area may be uncomfortable for a few hours to several days, and the patient may be unable to bear weight on it. A haemorrhagic blister may occur.

Repeated at three-weekly intervals, cryotherapy has an approximate cure rate of 65% at three months.Treatment can be extended beyond three months if necessary.

Topical commercial preparations

A commercial preparation containing about 17% salicylic acid and 17% lactic acid in collodion ('Duofilm' or 'Dermatech Wart Treatment') is applied daily after showering. The preparation is allowed to dry and the wart covered with waterproof tape, which is removed after the next shower or bath. The wart is pared once a week with a size 15-scalpel blade by the patient or a family member. It may take many months to clear the wart.

Formalin in aqueous solution

A mixture of 20% formalin in aqueous solution (25 mL ordered by script) is applied daily after showering. The wart is pared once a week with a size 15-scalpel blade. It may take many months to clear the wart.

Upton's paste

A piece of thick adhesive tape (eg, 'Leukoplast'), with a hole cut in the middle for the wart, is applied to the sole. Upton's paste is applied to the wart and the whole area occluded with a second piece of tape. This is kept dry and intact for one week. The wart is then pared and the paste reapplied until clearance occurs. Upton's paste consists of six parts salicylic acid and one part trichloroacetic acid in glycerine, mixed to a stiff paste (ordered by script).

Salicylic acid in white soft paraffin

A mixture of 40 to 60% salicylic acid in white soft paraffin is applied daily after showering and covered with waterproof tape. The wait is pared once a week with a size 15-scalpel blade by the patient or a family member.

Formalin soaks

The patient is prescribed formalin BP solution 37% (200 mL, 2 repeats) and instructed to make up a 3% solution on a daily basis. This is done by adding two teaspoons of the solution to one cup of water. The affected area is soaked in a shallow dish for 20 minutes daily. Before treatment, Vaseline is applied to the interdigital areas and the normal skin surrounding the wart. Once a week the wart is pared with a size 15-scalpel blade.

Note: Excision is generally not recommended for plantar warts as it may leave a painful scar and wart recurrence in the scar is common.

COMMON WARTS (VERRUCA VULGARIS)

These occur on any skin surface but most commonly on the hands, peri-ungual areas, fingers and knees. Peri-ungual warts, often found in nail biters, can cause nail dystrophy.

First-line treatment of common warts

Liquid nitrogen with a hand-held spray unit

The wart is frozen for up to 30 seconds. There is no advantage in using a double-freeze thaw cycle for hand warts. Cure rates are related to the number of treatments received, regardless of the interval between treatments (one, two or three weeks). A more rapid cure may be achieved by more frequent treatments.

A tender blister is expected.Liquid nitrogen is best avoided in darker-skinned patients, as permanent hypopigmentation may occur. Rare complications include damage to the nail matrix when treating periungual warts (which can cause permanent nail dystrophy) and nerve damage from overtreatment of warts overlying nerves.

Commercial preparations. See plantar warts.

Formalin in aqueous solution. See plantar warts.

Second-line treatment of common or plantar warts

Oral cimetidine

Some studies have suggested cimetidine is effective for multiple resistant warts, and many dermatologists believe this. However, a recent double-blind controlled study showed no beneficial effect compared with placebo. Supporters of this treatment feel it is more effective in children than adults. The dose is 20 to 40 mg per kg per day to a maximum of 3.5 g per day in adults. A three to four-month trial is usually undertaken.

Hyperthermic treatment

The affected area is immersed in hot water (45-48'C) for 90 minutes daily. It may take many months to clear the wart.

Intralesional bleomyein

Due to the severe pain associated with intralesional bleomycin, the area is usually anaesthetised first. The wart may be painful for two to three days, after which the wart blackens and a haemorrhagic crust develops.Complications include persistent pain after injection, local necrosis, Raynaud's phenomenon and nail dystrophy. After a four week interval, treatment may be repeated if necessary.

Laser therapy

Carbon dioxide laser is occasionally used for resistant warts. Local anaesthetic is necessary and healing may be prolonged. Complications include scarring, hyperpigmentation and hypopigmentation. Local recurrence of warts may occur.

Oral retinoids

In immunocompromised patients (eg, post-renal transplant) with extensive precancerous skin warts, systemic retinoids may reduce the bulk of the warts and decrease malignant change. Treatment does not generally lead to cure in these patients.

Spontaneous regression of common and plantar warts

Spontaneous regression of common and plantar warts is often heralded by darkening, the presence of thrombosed vessels and the tendency for the wart to desiccate.  Return of normal dermatoglyphies is a sign of resolution whether spontaneous or as a result of treatment.

FACIAL WARTS

These are generally plane (flat) warts or filiform warts.

Plane warts

Plane warts are smooth, flat-topped papules with minimal scale, most commonly found on the face, backs of hands and legs. They frequently occur at sites of trauma (the Koebner phenomenon).

Plane warts on the face occur in all age groups. Men with warts in the beard area and women with warts on the legs should avoid shaving until after treatment, as shaving spreads the virus.Women with facial warts should avoid cosmetics and creams, which may also spread the virus.

Treatment of plane warts

Cryotherapy

Each wart requires only a few seconds of liquid nitrogen cryotherapy with a hand-held spray unit. Care is taken with deeply pigmented patients as permanent hypopigmentation may occur. The treatment may need to be repeated on a number of occasions.

Topical retinoids (eg, tretinoin 0.05 % liquid)

This is applied second daily initially and increased to daily or twice daily as tolerated. Topical retinoids may cause local irritation such as erythema or scale and may take a number of months to become effective. Topical retinoids should be avoided in pregnancy, as they are teratogenic.

Spontaneous regression of plane warts is heralded by itch, erythema and oedema.

Filiform or sessile warts

Filiform warts can be treated either with cryotherapy or with gentle cautery under local anaesthesia. Either of these treatments may leave permanent hypopigmentation and cautery may result in scarring.

ANOGENITAL WARTS

Clinical anogenital warts can be detected with good light and magnification. Subclinical warts may become visible after a three-minute application of 5% acetic acid.

Condylomata acuminata are hyperplastic cauliflower-like lesions occurring on the perineum, genitalia or perianal area. Discrete 1 to 3 mm sessile or filiform warts and lesions resembling common warts also occur in these areas.

Affected females need to have regular pap smears.Female partners of affected male patients also need to be assessed.Other STD investigations should be performed as appropriate.

First-line treatment options of anogenital warts

Imiquimod is an immune response modifier, which stimulates the production of interferon alfa, tumour necrosis factor and other cytokines. The cream is applied at bedtime three times a week, left for six to 10 hours, then washed off. Treatment should be continued until there is total clearance of the warts or for a maximum of 16 weeks. The treatment is usually well tolerated. Its advantages are that it is self-administered and recurrence rates are low (about 13%). The disadvantage is that it is costly. Between one and four months of treatment is usually necessary. Females respond better, about 70% (as opposed to 33% of males) achieving clearance. Overall, 50% of patients treated achieve total clearance. Local reactions include erythema, oedema, induration, vesicles, erosion, ulceration and excoriation.A rest period of several days may be necessary. .

Podophyllotoxin

Podophyllotoxin 0.5% is applied twice daily for three consecutive days followed by a four-day rest period.  The cycle is then repeated.Clearance rates range from 45 to 75% and recurrence rates from 30 to 70 per cent. Application of excessive amounts does not increase cure rates but the frequency and intensity of local side effects. The advantages of podophyllotoxin over podophyllin are that it is self-applied and lacks systemic toxicity. Podophyllotoxin should be avoided in pregnancy and lactation. Local reactions, such as inflammation, burning and superficial erosions, occur in 50% of patients.

Podophyllin solution

Podophyllin solution is prescribed in concentrations of 10 to 25% in tincture benzoin. It is applied weekly by the doctor, left on for four to eight hours, then washed off.

Local reactions include burning and irritation. It is contraindicated in pregnancy, or when treating large areas or bleeding lesions.Rare systemic reactions include intra-utero death, vomiting, bone-marrow suppression, renal and liver toxicity, peripheral neuropathy, coma and death.

Liquid nitrogen cryotherapy

The lesion is frozen until there is a solid disc at the base. The procedure can be uncomfortable. Oedema (and sometimes blistering) occurs within 24 hours, and a small ulcer may appear. The procedure may need to be repeated. Clearance rates range from 50 to 80% and recurrence rates from 20 to 80 per cent.

Second line treatment of anogenital warts

Electro-surgery, electro-cautery and laser therapy

These treatments are indicated for large or recalcitrant lesions.Local or general anaesthesia is usually required. The total cure rate is 20 to 65 per cent.

Intralesional interferon

With new more efficacious treatments such as imiquimod, the use of intralesional interferon in the management of genital warts appears be decreasing. Recombinant interferon alfa-2b is injected three times a week for three weeks. Common side effects include local reactions and a flu-like illness during the first week of therapy.

J Am Acad Dermatol 1996, 34(6):1005-1007. extracted from 11 JUNE 1999 MEDICAL OBSERVER