Hidradenitis suppurativa: identification, symptoms and management

Introduction

Hidradenitis suppurativa (HS) is a chronic skin condition that causes painful inflammatory lesions in the folds of skin in areas of the body such as the armpits and groin, where hair follicles and apocrine sweat glands are present in abundance^​1​.

As well as the pain and discomfort of the growths, patients struggle with the social impact of the disease, with HS patients experiencing an estimated 50% higher risk of depression and double the risk of suicide^​2,3​. The appearance of deep-seated lesions can be unsightly and it can be embarrassing to have exudate leaking from the affected areas into clothing, with the fluid sometimes having an unpleasant odour as a consequence of pathogen infiltration^​4​.

Compared with other follicular disorders, such as acne, HS is less well recognised by healthcare professionals. Prevalence is difficult to pinpoint owing to varied estimation methodologies and patients are often misdiagnosed, waiting years for a firm diagnosis^​5​. Results from a 2018 study suggested that the condition may affect between 0.8–1.2% of the UK population^​2​. 

There is often a long diagnostic delay for patients; the average diagnostic delay for HS is 7.2 years^​5​. Incorrect diagnoses owing to healthcare professionals’ unfamiliarity with HS and patient delay in seeking professional help are theorised as likely reasons^​6​. Raising awareness of the disease among pharmacists and pharmacy technicians is one way in which this delay may be shortened.

Pathophysiology 

The name hidradenitis is a misnomer that derives from an outdated understanding of the pathophysiology of the disease: ‘hidrós’ means sweat, ‘adeno’ means gland and ‘itis’ refers to inflammation^​7​. Despite HS lesions being found in locations that are dense with apocrine sweat glands, it is thought that the pathophysiology of the disease is not directly related to the glands, but instead resulting from inappropriate immune function, as well as blockages in hair follicles and their associated structures^​7​.

Normal structure of the hair follicle can be seen in Figure 1^​8​, a suggested mechanism for the pathophysiology seen in HS can be seen in Figure 2^​9​.

Reproduced with permission from Martel et al.; StatPearls Publishing LLC

Smoking and obesity seem to contribute to disease progression by encouraging a pro-inflammatory environment; obesity can also contribute to increased mechanical stress and friction in the skin folds^​7​. Despite many logical theories, a definitive pathophysiology of HS remains elusive. 

Signs and symptoms 

The clinical presentation of HS can vary, but the characteristic signs are painful inflamed nodules, papules and pustules, double-ended pseudocomedones (blackheads) and cysts that merge together to form draining sinuses^​4​. Lesions can join together, forming tunnels under the skin and leaving scars and painful rope-like tethers of scar tissue^​1​.

The armpits, groin and under the breasts are common locations for lesions to develop; these are areas where friction regularly occurs during movement. Their warmth, plus the combination of high moisture levels and low oxygen permeability, appear to help the proliferation of anaerobic bacteria, the presence of which may trigger the inflammatory response at the start of a HS lesion^​1​.

The affected areas are typically hidden under clothing, which can make it difficult to identify a potential case of HS in a pharmacy setting, unless a patient proactively seeks advice. Pharmacists can help support patients in appropriate use of over-the-counter pain management and the selection of dressings, which will be discussed in more detail later.

Unfortunately, scarring is common and can be just as debilitating as active HS lesions themselves in high-grade disease. Patients develop hypertrophic and bridging scars that rigidly connect skin on the inside of joints, potentially limiting range of motion in the limbs^​4​. Scar tissue can be extensive and can have a significant impact on quality of life^​10​.

Risk factors 

Studies have found that women are three times more likely than men to be diagnosed with HS in Europe and North America^​2,11​. It is more common in people with skin of colour; US studies have shown people from racial and ethnic minority groups have a higher prevalence of HS and greater disease morbidity^​12​. There also appears to be a genetic link; family history is reported in around one-third of patients^​5​. A history of other follicular disorders, such as acne and pilonidal sinus, as well as diseases of immune dysregulation, such as Crohn’s disease, ulcerative colitis and psoriasis, have been found to have an association with HS^​5​.

HS patients are more than three times more likely than the general population to smoke or have obesity, making these the two biggest modifiable risk factors for the disease^​2​. Smoking cessation and support in weight loss are areas where community pharmacy teams can be of great help, through advanced services, counselling and signposting to other NHS resources. However, expectation management is important. Although positive changes to these risk factors can reduce disease severity in patients, it is not a silver bullet and HS is still found in patients who are non-smokers, and in those of a healthy weight^​4​.

Diagnosis and grading

HS is usually a clinical diagnosis owing to characteristic lesion sites/morphological features, strong links to family history of the disease and association with other follicular or immune function disorders^​13​. Comprehensive history-taking and physical examination are, therefore, critically important. Histological investigation is uncommon, as it is difficult to distinguish the disease from other inflammatory skin conditions under the microscope^​14​. More information on diagnosis can be found in the British Association of Dermatologists’ HS 2018 guideline^​4​.

Once a diagnosis has been made, there are many severity scoring systems available to clinicians; however, the Hurley staging system is most widely used in the UK (see Table 1^​4​). Severity scoring systems are important to monitor disease progression and for effective communication between primary, secondary and tertiary care teams when progressing to more specialist treatment options with complex funding arrangements.

There are various differential diagnoses for HS. What might appear superficially to be HS, could be cutaneous manifestations of Crohn’s disease, staphylococcal infection or cysts^​7​. Prompt signposting of patients to general practice and specialist services is the most suitable approach for pharmacists to take. The intimate location of many HS growths means that axillary lesions are the only common lesion site that would be appropriate to examine in the consultation room of a community pharmacy.

Management

Treatment regimens can be complex and may involve drugs with important counselling points. Patients may need to be reviewed each month or so during the initiation of a treatment, but this can become more infrequent once stabilised (perhaps every three to six months instead)^​4​. In hospital dermatology services, pharmacists can support access to new treatment options, such as monoclonal antibodies^​15,16​. They can also directly engage with and prescribe for patients in clinics and encourage other clinical staff in the department to adhere to step-wise treatment pathways based on national guidance^​4​, supporting patients in finding the best treatment regimen for their disease. 

Treatment success is assessed based upon reduction in pain and lesion count, more infrequent disease flares and by improved scores on quality-of-life questionnaires^​4​.

Conventional therapies

Patients often cycle through a variety of pharmacological interventions in pursuit of relief from HS. Antibiotics feature prominently in the treatment algorithm from the British Association of Dermatologists^​4​. The mechanism by which antibiotics alleviate HS may be as much owing to their anti-inflammatory and immunomodulatory effects as their antimicrobial function^​17​.

The benefit of long courses of antibiotics (i.e. more than 14 days) for the individual patient, combined with the chronic nature of HS, presents a dilemma: while some patients are keen to use an antibiotic on an ongoing basis, antimicrobial stewardship is increasingly important and pharmacists should challenge open-ended use of antibiotics in this patient group. That is not to say that an individual should be limited to a set number of courses in a lifetime, but antibiotic regimens should have a defined endpoint and only be reinitiated in times when symptoms flare^​4​.

There are some notable adverse effects for systemic HS regimens. Pharmacists can counsel patients on the important safety points and ensure suitability. Generally, the least intense and most cost-effective options are tried in the first instance, progressing to more intensive options in later lines of treatment, requiring careful consideration as to the balance of risks versus benefits. This is explored in Table 2^{​4,18–23​}.

The monoclonal antibodies adalimumab and secukinumab, which are the last lines of treatment, require centrally commissioned NHS funding^{​15,16,24​}. They can be used only when conventional systemic therapies have failed. Their benefit in HS is mediated through effects on inflammatory pathways (affecting the cytokines tumour necrosis Factor α and Interleukin 17, respectively)^​24​. The treatments are suitable for shared care between secondary and tertiary care^​15,16​. However, the mechanism for ensuring appropriate reimbursement can be confusing for clinical teams. Pharmacists can make use of their expert knowledge on funding pathways to make sure that costs are appropriately reimbursed. By enabling shared care, pharmacists can make it easier and more convenient for patients to be supported by their local dermatology team, rather than having to be managed by a more distant specialist centre.

Pain management

Pain is considered to be the most impactful symptom of HS for many patients^​25​. There is currently no clear consensus on optimal pain management and there is a pressing need for research to understand the causes of HS pain. Pain in HS appears to involve a combination of both neuropathic and nociceptive pathways^​26​. Pharmacists can support patients in finding relief with over-the-counter products, such as oral or topical NSAIDs, given the inflammatory nature of the disease, or with topical methol (a medication that relieves pain by causing the skin to feel cool and then warm), which can be soothing when used on impacted sites^​27​.

Paracetamol can be useful in mild pain; however, refractory pain may require prescription-only medicines, such as gabapentin, tricyclic antidepressants or opioids^​27​. Involvement of specialist pain teams is prudent, given the potential for dependency with these more intensive options. Healthcare professionals should also bear in mind that an individual’s experience of pain does not necessarily correlate with the outward markers of disease severity.

Self-care advice

Patients can also benefit from other treatment modalities and lifestyle adjustments. Some patients find the use of an antiseptic wash such as chlorhexidine 4% solution beneficial as a soap substitute^​4​. Avoiding tight-fitting clothing that could otherwise add to friction and occlusion can help some patients. A system of dressings and custom garments called Hidrawear is available on some formularies in the UK, which has been developed to reduce friction and incorporates dressings that lock into place at common HS lesion sites^​28​. Patients who require additional support with wound care can be signposted to speak with specialist dermatology nurses or members of the local tissue viability team, who are best placed to provide expert individualised advice. As a general guide, the most suitable dressings for HS are usually those that have high absorbance and low friction. Charcoal dressings can also help manage odour^​29​. 

Surgery

Surgery is used to remove chronic lesions that have not responded to medical intervention and to address sequelae, such as scars, contractions of the skin and sinus tracts^​24​. Novel surgical techniques are evolving to suit the morphological characteristics of HS, such as de-roofing, in which the roof of a lesion is excised. This can save tissue and reduce lesion recurrence^​30​. Marsupialisation is another procedure whereby the surgeon crafts a pocket of tissue at a lesion site with an intentional opening that the patient can manually manipulate to easily drain exudate at a convenient time, reducing pain from fluid build-up and minimising the risk of embarrassing leakages in social situations^​10​. Patients can experience complications as a consequence of surgery, with the potential for infection and nerve damage. Scar tissue from the surgery itself might still limit the range of motion of limbs^​7​. There is evidence to suggest that specialist surgical techniques lead to low levels of recurrence for the lesion that has been operated on; however, there is always the risk of new lesions developing in the future^​31​.

Complications and patient prognosis 

HS patients have an elevated risk of squamous cell carcinoma owing to chronic inflammation^​7​. Medical interventions are not without risk, as shown in Table 2. Monitoring for adverse events when using intensive treatments is important. There is significant overlap between the disease and comorbidities, such as cardiovascular problems, atherosclerosis, metabolic syndrome, diabetes mellitus and hyperlipidaemia^​4,7​.

Conclusion

The past 20 years have revolutionised the pharmacological landscape for other inflammatory dermatoses, such as psoriasis and atopic dermatitis, with a wealth of effective, targeted treatment options now on offer^​32​. Unfortunately, the same cannot be said for HS. Although new treatment options, such as monoclonal antibodies, are promising, managing expectation in patients while still being able to elicit the enthusiasm to pursue different treatments is a delicate balancing act. Identification and early treatment of HS can reduce the likelihood of developing severe disease^​6​.