Introduction
Hidradenitis suppurativa/acne inversa (HS) is a chronic, inflammatory, recurrent, debilitating skin disease of the hair follicle which affects apocrine gland-rich areas of the body. The disease usually presents after puberty, but it can, although uncommonly, also affect adolescents (onset after initiation of puberty, older than 10 to 12 years) and children. Typical clinical symptoms include painful, deep-seated, inflamed lesions (nodules, abscesses), tunnels, and scarring. In this chapter, we present the main aspects of the disease in pediatric populations. The major features of HS in children and adolescents are summarized in Table 29.1 .
| Epidemiology | 2%–8% of HS patients Rare in children (≤ 10 years), uncommon in adolescents (after initiation of puberty > 10–12 years) |
| Predisposing factors | Obesity (50%–70% overweight or obese) Tobacco exposure
Genetic predisposition |
| Clinical features | Axillary and inguinal regions most commonly involved Mostly mild or moderate severity Similar clinical course as adults Female predominance |
| Severe complications (rare) | Infections Fistulas to surrounding organs (e.g., urinary bladder, rectum, etc.) Anemia Lymphedema |
| Comorbid disorders | Obesity/metabolic syndrome Dermatologic conditions Hormonal disorders Down´s syndrome Hypothyroidism Pyoderma gangrenosum Psychiatric disorders |
| Therapy | Topical
|
Pathogenesis
Pathogenetic mechanisms of HS are not yet fully elucidated. In general, genetic susceptibility, obesity/metabolic syndrome, and smoking have been implicated. A positive family history is often observed in patients with early onset of the disease. Familial occurrence varies from 20% to 55% among different studies, whereas a small Danish cohort of obese children reported a positive family history in 80% (4/5) of the patients. Moreover, genetic predisposition may also lead to pediatric HS. Mutations in the γ-secretase genes complex as well as aberrations in the Notch signaling cascade are implicated in the inflammatory process. Data from case reports or small case series show that early-onset HS is also associated with underlying hormonal disorders, such as precocious puberty, premature adrenarche, or adrenal hyperplasia. These conditions are more commonly seen in children than in adults with HS. In the pathogenetic pathway of pediatric HS, the elevated sensitivity of the pilosebaceous unit to circulating sex hormones has also been postulated. Moreover, apocrine glands may also be secondarily involved. Apocrine glands become active during puberty. They empty their content into the follicular canal and not into the skin surface in contrast to eccrine glands. Keratinocytes of the pilosebaceous unit contain androgen receptors, which may promote follicular plugging due to hyperkeratinization, resulting in inflammation, rupture of follicles, abscess, and tunnel (sinus tract) formation.
Another factor propagating HS in adult and pediatric patients is obesity. Recent data suggest that the majority of patients are overweight or obese, with a reported rate varying from about 50% to 80%. Additionally, obesity is likely associated with a more serious disease course as well as precocious puberty. In a recent multicenter study, patients’ body mass index (BMI) were correlated with the average parent BMI, showing that our therapeutic approach and weight counseling strategies should also include the patient’s family.
Despite being a pivotal player in adult HS cases, smoking habits do not seem to play a key role in cases of early-onset HS. According to recent studies, only a small proportion of pediatric HS patients were active smokers. However, bear in mind that children may be subject to passive tobacco exposure.
Epidemiology
Overall, HS has a prevalence of 0.03% (Europe) to 0.053% (USA) and a calculated prevalence of 0.4%. Pediatric HS seems to represent a rather small cluster of the disease. However, the data regarding disease onset shows a wide age range. Although older reports documented an early onset in 2% of HS patients, a recent study from the Netherlands reported that 8% of patients show a disease onset before the age of 13.5 years, whereas according to an Italian study, 90 out of 235 patients (38%) recalled that the first symptoms occurred before the age of 16. On the other hand, a recent US cohort study presented an overall standardized prevalence of 0.02% for pediatric HS patients (0 to 17) and demonstrated that the pediatric age group only represents 1020 of 47620 documented HS cases in the USA (2.2%), affecting pediatric patients of African American or biracial descent significantly more often. A very young disease onset in prepubertal patients (age 10 years or younger), with or without precocious puberty or premature adrenarche, has only been presented in case reports or small case series.
Clinical Features
HS in pediatric patients is also characterized by the presence of inflammatory nodules, abscesses, tunnels, and scarring in the apocrine gland-rich areas of the body. According to recent data, it seems that most subjects suffer from a mild or moderate disease and show a similar clinical course when compared with adult patients. However, it has been suggested that pediatric patients may not have reached their peak severity. Ethnicity may also affect the clinical course and areas of involvement in HS patients. Cases with excessive scarring and numerous abscesses and sinus tracts have been documented. In most patients, the axillary and inguinal regions are involved, although with varying frequency among different studies. Other affected anatomic areas include the buttocks, the submammary area, and the mons pubis. Additionally, most recent studies have demonstrated a female predominance in cases of early-onset HS.
Complications
The clinical course of HS in children and adults may be complicated by a wide variety of sometimes serious clinical conditions, such as anemia, lymphoedema, and fistulae to the surrounding organs (urinary bladder, rectum, etc.). Additionally, various, occasionally life-threatening cutaneous, extracutaneous, and systemic infections may also complicate the course of HS patients. Theoretically, HS patients represent a high-risk group for potential infections due to the dysfunction of the epidermal barrier, treatment with immunomodulators/immunosuppressants, and associated comorbidities, such as diabetes mellitus. However, infections in HS patients are rarely documented.
Scoring Systems
The most commonly used classification system is Hurley’s classification. Dynamic scoring systems used to assess disease severity in adults are also applied in pediatric patients and include the International Hidradenitis Suppurativa Severity Score System (IHS4), the Sartorius score, and the HS Physician Global Assessment (HS-PGA), whereas Children’s Dermatology Life Quality Index (CDLQI) is used to evaluate the influence of HS on patients’ quality of life.
Comorbid Disorders
Various studies, case series, and case reports have tried to identify the most common comorbid disorders associated with HS. In most cases, a statistically significant difference between early and adult onset could not be documented. The most commonly reported comorbid disorder is acne vulgaris. Furthermore, pediatric HS patients display a wide variety of other dermatological conditions such as atopic dermatitis, hirsutism, pilonidal sinus, seborrheic dermatitis, and acanthosis nigricans. As mentioned before, in some early onset cases, hormonal dysregulation, such as premature adrenarche, precocious puberty, congenital adrenal hyperplasia, and polycystic ovary syndrome, may play a pivotal role in the pathogenetic mechanism and/or propagation of HS. Recently, the association of pediatric HS with metabolic disorders/syndrome, including obesity, diabetes mellitus, hyperlipidemia, and hypertension, has also been highlighted. Additionally, autoimmune/autoinflammatory conditions, such as rheumatoid arthritis, inflammatory bowel disease, and various inflammatory disorders, may also associate with HS. Other conditions, including hypothyroidism, pyoderma gangrenosum, and HIV infection, have also been reported. A small proportion of early-onset HS, about 2% to 5%, coexists with Down syndrome, while a prevalence of 38% was reported in a study from Saudi Arabia. a
a References .
Finally, it must be noted that affected individuals often suffer from psychiatric conditions due to a significant life quality alteration and fear of stigmatization, which further perplex the clinical course and management of HS patients.Treatment
Therapeutic strategies in pediatric HS patients are based on the guidelines for adult patients and depend on the disease severity. Despite being relatively widely used, they are based on extrapolations that highlight the need for specific pediatric HS guidelines. In general, mild cases are treated with topical agents, whereas more severe cases are treated with antibiotics or biologics. Extended or resistant disease may sometimes require a surgical approach. Pain management, weight counseling, and psychological consulting should also be included in the therapeutic arsenal. In the treatment of early-onset HS, the management of comorbid disorders as well as complications such as severe infections are also essential.
Topical
Clindamycin 1% gel applied twice daily for 3 months seems to be the treatment of choice for most mild cases. A recent study suggested the topical use of resorcinol; however, its use should probably be avoided due to lethal cases of resorcinol poisoning in infants and young children. Azelaic acid and chlorhexidine or zinc pyrithione washes have also been used.
Systemic
Systemic therapeutic approaches may be needed for patients who do not respond to first-line topical agents, or in more severe cases. In such cases, antibiotic treatment with tetracyclines or clindamycin alone or in combination with rifampicin, in adapted dosing for children and adolescents, is preferred. Tetracyclines should not be used before the age of 8 years, as they can cause an irreversible discoloration of the permanent teeth. Doxycycline displays the lowest affinity for calcium binding and has the lowest risk of teeth or bone discoloration. Additionally, the use of azithromycin has been proposed to control the flares. However, in severe cases, biologics combined with surgery may be needed. Adalimumab is the only approved biological treatment for HS in adults and children older than 12 years with moderate or severe HS. Infliximab has been administered off-label in non-responders as a second-line therapy, while treatment with Anakinra has been mentioned in small case series. Dapsone, finasteride, oral contraceptives, oral zinc supplementation, photodynamic therapy, and intralesional injection of corticosteroids or botulinum toxin A are also regarded as alternative treatment options. Isotretinoin did not prove to be effective in adults with HS, and its use is not recommended when treating children for HS.
Surgery
Pediatric patients may also need surgical treatment in cases of severe and extensive HS. Surgical management seems to be relatively safe and effective, although there is a risk of recurrence. Deroofing or total excision (local or wide) of the affected area has been used. A simple incisions has been proven ineffective in most cases, although they are sometimes used to manage an acute painful abscess. Recently, an endoscopic approach for the treatment of tunnels has been proposed, following a procedure similar to the treatment of pediatric endoscopic pilonidal sinus. Laser therapy with a fractionated CO 2 laser is another effective treatment option with a relatively good safety profile, especially for the management of scarring. Neodymium-doped yttrium aluminum garnet (Nd:YAG) lasers, as well as intense pulsed light, can be used for hair removal.
Adjuvant Therapeutic Strategies
Apart from the standard treatment of HS, the diagnosis and management of complications such as anemia and infections are of crucial importance. It is also important to notice that endocrine and metabolic disorders should be diagnosed early and treated properly. Weight reduction strategies and nutrition counseling, as well as pain management and psychological support, should also be included in the therapeutic arsenal.
Conclusion
HS in children is rare and uncommon in adolescents with varying prevalence among different studies. The disease shows a similar clinical course to adult patients, with most subjects exhibiting a mild or moderate severity. The majority of pediatric patients are overweight or obese and non-smokers, with a female predominance. Acne vulgaris, accompanying infections, and endocrine, metabolic, or psychological disorders may complicate the clinical course. Treatment is based on guidelines for adult patients and depends on disease severity. Management of mild cases includes topical measures such as clindamycin gel, whereas antibiotic treatment or biologics should be used for more advanced cases. Surgical management should also be considered for more severe or refractory cases. Therapeutic algorithms should also include pain management, treatment of superinfections, weight counseling, and psychological consulting.
References
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