Acne vulgaris: Diagnosis and management

ACNE VULGARIS

What is it?

Acne vulgaris is a chronic inflammatory skin condition affecting mainly the face (99% of cases), back (60% of cases) and chest (15% of cases).

Acne is characterised by blockage and inflammation of the pilosebaceous unit (the hair follicle, hair shaft and sebaceous gland). It presents with lesions which can be non-inflammatory, inflammatory or a mixture of both.

Non-inflamed lesions are known as comedones, which may be open (blackheads), closed (whiteheads) or microcomedones (clinically invisible).

Inflammatory acne lesions include papules and pustules (5 mm or less in diameter) – in more severe disease these can develop into larger deeper pustules and nodules.

Most people with acne have a mixture of inflammatory and non-inflammatory lesions.

There is no universally agreed grading system for acne but it is often categorised by lesion type and severity into:

• Mild acne – predominantly non-inflamed lesions (open and closed comedones) with few inflammatory lesions.
• Moderate acne – more widespread with an increased number of inflammatory papules and pustules.
• Severe acne – widespread inflammatory papules, pustules and nodules or cysts. Scarring may be present.

Conglobate acne is a rare and severe form of acne found most often in men. It presents with extensive inflammatory papules, suppurative nodules (which may coalesce to form sinuses) and cysts on the trunk and upper limbs.

Acne fulminans is a sudden severe inflammatory reaction that precipitates deep ulcerations and erosions, sometimes with systemic effects (such as fever and arthralgia).

What causes it?

The pathogenesis of acne is not completely understood but is thought to involve several processes including:

• Altered follicular keratinocyte proliferation leading to formation of follicular plugs (comedones).
• Androgen induced seborrhoea (increased sebum production) within the sebaceous follicles which usually occurs around puberty.
• Proliferation of bacteria (such as Propionibacterium acnes) within sebum in hair follicles.
• Inflammation of the pilosebaceous unit.

Studies have suggested that other factors may contribute to the pathogenesis of acne such as:

• Genetic factors – a high concordance between identical twins and a tendency towards severe acne in people with a positive family history has been identified.
• Racial and ethnic factors – the prevalence, severity, clinical presentation and sequelae of acne varies between different population groups.
• Diet – recent studies suggest there may be a correlation between acne and high glycaemic index diets.

How common is it?

An estimated 650 million people are affected by acne worldwide. Prevalence varies widely in different geographical areas, with Western industrialised countries having much higher rates of acne than some non-industrialised countries. Up to 95% of adolescents in Western industrialised countries are affected by acne to some extent – 20 to 35% develop moderate or severe acne.

Of people with acne, approximately:

• 85% are aged 12–24 years.
• 8% are aged 25–34 years.
• 3% are aged 35–44 years.

Acne is more common in males during adolescence, but in adulthood incidence is higher in women.

Acne is one of the most common skin conditions in the UK, leading to 3.5 million visits to primary care every year.

What are the complications?

• Skin changes:
• Scarring — acne may result in hypertrophic or atrophic scars which can be extensive.
• Post-inflammatory hyperpigmentation or depigmentation can occur.
• Psychosocial effects
• Acne is associated with significant psychological problems including an increased risk of depression, suicide, anxiety, reduced attachment to friends, and low self-esteem.

What is the prognosis?

Acne is a chronic disease that can persist for many years. It tends to affect adolescents and usually resolves after the end of growth, but it may persist into adulthood as a continuation of adolescent acne or due to development of late-onset disease. Females are more likely than males to have acne in adulthood – the predictive factors for persistence into adulthood are not clear.

DIAGNOSIS: WHAT ARE THE CLINICAL FEATURES OF ACNE VULGARIS?

Acne affects areas of the body with a high density of pilosebaceous glands such as the face, chest and back. Clinical features vary widely depending on severity and the person affected.

Comedones must be present for a diagnosis of acne to be made. If they are not present other diagnoses should be considered.

Suspect acne in a person presenting with:

• Non-inflammatory lesions (comedones) that may be open (blackheads) or closed (whiteheads).
• Inflammatory lesions such as:
• Papules and pustules – superficial raised lesions (less than 5 mm in diameter).
• Nodules or cysts (larger than 5mm in diameter) – deeper, palpable lesions that are often painful and may be fluctuant. In very severe acne nodules may track together and form sinuses (acne conglobate).
• Scarring – atrophic/ice pick or hypertrophic/keloid scars may be seen.
• Pigmentation – post-inflammatory depigmentation or hyperpigmentation may be present.
• Seborrhoea – commonly present.

There is no universally agreed scoring system for acne severity but categorising into mild, moderate and severe can be helpful in selection of appropriate treatment and monitoring of response:

• Mild acne: predominantly non-inflamed lesions (open and closed comedones) with few inflammatory lesions.
• Moderate acne: more widespread with an increased number of inflammatory papules and pustules.
• Severe acne: widespread inflammatory papules, pustules and nodules or cysts. Scarring may be present.

How should I assess someone with suspected acne vulgaris?

Take a history, asking about:

• Duration, type and distribution of lesions.
• Previous treatment (including over-the-counter medications) and response.
• Exacerbating factors such as flares with menstruation, contraceptives, cosmetics, face creams or hair pomades.
• Systemic features – some rare subtypes of acne (acne fulminans) can present with systemic features including fever, arthralgia, and myalgia.
• Psychosocial impact of acne – ask about psychological problems including anxiety and low mood.
• Family history, including endocrine disorders, polycystic ovarian syndrome, acne and other skin conditions.
• Possible underlying causes:
• Drug history – some medications can cause or exacerbate acneiform rashes including androgens, corticosteroids, isoniazid, ciclosporin and lithium.
• Hyperandrogenism – may present with irregular periods, androgenic alopecia or hirsutism in women.

Examine the person and look for:

• Clinical feature of acne such as non-inflammatory comedones and inflammatory papules, pustules, nodules and scarring.
• Comedones (must be present for a diagnosis of acne to be made. If not present, consider alternative diagnoses). Record the type and distribution of lesions and severity.
• Signs of other disorders than can present with acne such as hyperandrogenism, or [blob]Polycystic ovarian syndrome.

Investigations

Most people with acne do not require any investigations.

Consider appropriate investigations/referral to endocrinology for people presenting with clinical features of polycystic ovary syndrome (such as menstrual irregularity and hirsutism), or other endocrinopathy.

Differential diagnosis – what else could it be?

The differential diagnosis for acne includes:

• Rosacea
• Perioral dermatitis
• Folliculitis and boils
• Drug-induced acne – some drugs can cause or exacerbate acneiform eruptions including dioxins (chloracne), pomades, corticosteroids, anti-epileptics (phenytoin and carbamazepine), lithium, isoniazid, vitamins B1, B6 and B12.
• Keratosis pilaris.

HOW DO I MANAGE SOMEONE WITH ACNE VULGARIS?

Explain the diagnosis, provide patient information and discuss treatment aims.

Advise the person:

• To avoid over cleaning the skin (which may cause dryness and irritation). Acne is not caused by poor hygiene and twice daily washing with a gentle soap and fragrance-free cleanser is adequate.
• If make-up, cleansers and/or emollients are used, non-comedogenic preparations with a pH close to the skin are recommended.
• To avoid picking and squeezing spots which may increase the risk of scarring.
• That treatments are effective but take time to work (usually up to 8 weeks) and may irritate the skin, especially at the start of treatment.
• To maintain a healthy diet.

Patient information is available from:

• NHS Choices – Acne
• British Association of Dermatologists – Acne

For people with mild-to-moderate acne

Consider prescribing a single topical treatment such as:

• A topical retinoid (for example, adapalene [if not contraindicated]) alone or in combination with benzoyl peroxide. Retinoids are contraindicated in pregnancy and breastfeeding
• A topical antibiotic (for example, clindamycin 1%). Antibiotics should always be prescribed in combination with benzoyl peroxide to prevent development of bacterial resistance. Topical benzoyl peroxide and topical erythromycin are usually considered safe in pregnancy if treatment is felt to be necessary.
• Azelaic acid 20%.

Creams or lotions may be preferable for people with dry or sensitive skin and less greasy gels may be preferable for people with oily skin. Concentration or application frequency of topical treatments may need to be reduced or lowered if skin irritation occurs.

Advise the person that frequency of application can be gradually increased from once or twice a week to daily if tolerated.

For people with moderate acne not responding to topical treatment

If response to topical preparations alone is inadequate consider adding an oral antibiotic such as lymecycline or doxycycline (for a maximum of 3 months).

• A topical retinoid (if not contraindicated) or benzoyl peroxide should always be co-prescribed with oral antibiotics to reduce the risk of antibiotic resistance developing.
• Macrolide antibiotics (such as erythromycin) should generally be avoided due to high levels of P. acnes resistance but can be used if tetracyclines are contraindicated (for example, in pregnancy if treatment is felt to be necessary).
• Change to an alternative antibiotic if there is no improvement after 3 months, the person is unable to tolerate side effects or acne worsens while on treatment.
• If the person does not respond to two different courses of antibiotics, or if they are starting to scar, refer to a dermatologist for consideration of treatment with isotretinoin.

Combined oral contraceptives (if not contraindicated) in combination with topical agents can be considered as an alternative to systemic antibiotics in women.

• Oral progesterone only contraceptives or progestin implants with androgenic activity may exacerbate acne, second and third generation combined oral contraceptives are generally preferred.
• Co-cyprindiol (Dianette®) or other ethinylestradiol/cyproterone acetate-containing products may be considered in moderate to severe acne where other treatments have failed but require careful discussion of the risks and benefits with the patient. Use should be discontinued 3 months after acne has been controlled and prescription guided by the UK Medical Eligibility Criteria for Contraceptive Use and the Summary of Product Characteristics for the individual product.

Refer the person to dermatology, with urgency depending on the clinical situation if:

• They have a severe variant of acne such as acne conglobata or acne fulminans (immediate referral is indicated).
• They have severe acne associated with visible scarring or are at risk of scarring or significant hyperpigmentation – primary care treatment should be initiated in the interim.
• Multiple treatments in primary care have failed.
• Significant psychological distress is associated with acne regardless of severity – primary care treatment should be initiated in the interim.
• There is diagnostic uncertainty.

Arrange follow-up

Review each treatment step at 8-12 weeks.

• If there has been an adequate response continue treatment for at least 12 weeks.
• If acne has cleared or almost cleared, consider maintenance therapy with topical retinoids (first line, if not contraindicated) or azelaic acid.
• If there has been no response consider adherence to treatment, adverse effects, progression to more severe acne, or use of comedogenic make up or face creams. Discuss a trial of an alternative formulation or move on to the next step in treatment if appropriate.

Resources

NICE. Clinical Knowledge Summaries; 2018. Acne vulgaris. https://cks.nice.org.uk/acne-vulgaris

NICE.Clinical Knowledge Summaries; 2018. Rosacea. https://cks.nice.org.uk/rosacea-acne

NICE.Clinical Knowledge Summaries; 2017. Boils, carbuncles, and staphylococcal carriage. https://cks.nice.org.uk/boils-carbuncles-and-staphylococcal-carriage

Archer C, Cohen S, Baron S. Guidance on the diagnosis and clinical management of acne. Clin Experiment Dermatol 2012;37(Suppl 1):1-6.

Asai Y, Baibergenova A, Dutil M, et al. Management of acne: Canadian clinical practice guideline. CMAJ 2016;188(2):118-126 BMJ Best Practice Acne vulgaris; updated 2018. https://bestpractice.bmj.com/topics/en-gb/101

Primary Care Dermatological Society. Acne: acne vulgaris; 2018 http://www.pcds.org.uk/clinical-guidance/acne-vulgaris

DermNet NZ Acne vulgaris. https://dermnetnz.org/topics/acne-vulgaris/