1. Clinical features
Despite being dismissed as just one of the many difficulties of adolescence, acne can have a significant impact on quality of life, sometimes for many years. But there are effective treatments available.
The cause of acne
Acne is the result of a blockage of the pilosebaceous duct, caused by hyperkeratosis at the mouth of the hair follicle. Clinically, this presents as an open comedone or blackhead. Sebum continues to be secreted into the duct from the sebaceous glands at the base of the follicle and this causes distension of the duct, to produce a closed comedone or whitehead. Sebum excretion is hormonally controlled. This is probably related to the follicle’s sensitivity to androgens, rather than to high levels of androgens.
The role of bacteria
The sebum is broken down by Propionibacterium acnes bacteria into triglycerides.
These are highly irritant and leads to an inflammatory response, represented clinically by erythematous papules. In addition, continued distension of the follicle eventually results in its wall breaking down.
The subsequent inflammatory reaction rapidly results in polymorphic leucocyte infiltration, causing erythematous pustules. If the inflammation is more aggressive, it can result in the development of nodules and cysts.
The healing phase of the inflammation can result in the pilosebaceous unit returning to normal, although an area of macular erythema can persist.
Severe inflammation will result in scarring, either ‘ice pick’ or raised hypertrophic scars.
Acne lesions can occur wherever there are sebaceous follicles. The most common sites are the face and trunk. Rarely, they may spread to the buttocks and proximal limbs. Lesions are discrete, as they are derived from individual pilosebaceous units.
When acne develops
Acne usually begins at puberty and most teenagers have it to some degree. In rare cases, it can occur before puberty.
Many patients continue to have acne in their twenties or thirties. Women over 20 can develop acne, especially around the mouth.
2. First-line treatment
These non-inflammatory lesions are best treated with a keratolytic peeling agent that removes the surface keratin and unplugs the follicular openings. Keratolytic agents include benzoyl peroxide, presented as a cream, lotion, aquagel, gel, or in combination (5%) with clindamycin (1%).
The retinoids come in several forms, such as tretinoin 0.01% or 0.025% gel and 0.025% lotion, and isotretinoin 0.05% gel.
Other agents include adapalene 0.1% cream or gel. Azelaic acid 15% gel or 20% cream can be used if inflammatory lesions are present as well as the comedones. Ultraviolet light has a similar effect on this condition as is found with the keratolytic agents.
Inflammatory lesions include papules, pustules or nodules and may need systemic therapy. In mild cases, continue with keratolytic agents that also have antibacterial activity and try a topical antibiotic. If the case is moderately severe, use long-term, low-dose antibiotics, or in female patients, anti-androgens.
Topical antibiotics work well, but can produce resistant bacteria on the skin surface and contact allergic eczema. It is best to use one that contains two antibacterial agents, such as zinc and erythromycin or benzoyl peroxide and clindamycin. These are applied once a day, usually at night in the case of benzoyl peroxide and clindamycin, or twice daily for the other combination. They are particularly useful in pregnancy, because there is negligible systemic absorption.
If an oral and a topical antibiotic are combined, the same agent should be used. It should be noted that there is no evidence that combining topical and systemic antibiotics is beneficial.
Antibiotics work in acne because of their antibacterial activity against acnes. They are also anti-inflammatory and reduce keratin in pilosebaceous ducts. Tetracyclines also scavenge superoxides formed from oxidation products of comedogenic unsaturated fatty acids in the skin.
Oxytetracycline 500mg twice daily is cheap and effective. It must be taken on an empty stomach more than half an hour before a meal.
Improvement in the condition is slow and may not be apparent for the first two or three months of treatment. If the antibiotic is continued, gradual improvement will continue for up to a year. Treatment with antibiotics should be given for at least six months, but if response is poor or relapse occurs after stopping the treatment, consider referring the patient to a dermatologist for oral isotretinoin.
3. Alternative treatments
If there is no response despite good compliance, other treatments must be considered.
Alternative antibiotics include erythromycin 500mg twice daily, which can be taken with food, and minocycline 50mg twice daily or as a 100mg sustained release.
Alternatives to minocycline include doxycycline 100mg once daily and lymecycline 408mg daily.
The anti-androgen cyproterone acetate is usually given at a low dosage of 2mg in Dianette. This formulation contains 35µg oestrogen. It is useful in women if antibiotics have not worked or if they require contraception.
The maximum effect does not occur for two or three months, and treatment needs to be continued in the long-term. It costs more than oxytetracycline or a normal oral contraceptive.
Patients whose acne does not respond to standard treatment, or is severe, should be considered for treatment with the oral retinoid isotretinoin. This has to be prescribed by a dermatologist so hospital referral is necessary.
Any patients with nodules or cysts that are producing scarring should be considered for referral.
Other indications include failure to control acne after six months’ antibiotic use, persistent acne in patients over 25 years-old and where there are associated emotional problems. It should be remembered that teenagers are at a sensitive stage in life and that dismissal of acne as ‘just some spots’ is unfair and inconsiderate.
Isotretinoin is the most effective treatment available for severe acne. It is given with food for four months as a single daily dose of 0.5mg to 1.0mg/kg body weight.
Long-term remission occurs, lasting from several months to being permanent, provided an adequate dose has been given. Patients must be encouraged to complete the course and attend for follow-up.
Isotretinoin is teratogenic, so women should not become pregnant while taking it, or for one month afterwards. This is the main reason for restriction to hospital prescription, although its cost is also a factor.
All patients experience dryness and splitting of the lips and will need to use a lip salve.
Dry eyes can be a problem, but wearing contact lenses is not necessarily a contraindication to treatment. Hypromellose eye drops may be needed.
Epistaxis secondary to dryness of the nasal mucous membranes can occur, as can muscle aches, especially after exercise.Women may experience irregularities or even cessation of their periods.
A temporary rise in serum lipids and liver enzymes occurs and initially there may be marked worsening of the acne, with multiple pyogenic granuloma-like nodules.
Rarely, isotretinoin therapy can induce depression, but this does not seem to be any more likely in those who are suffering from, or prone to, depression.