Topical and intralesional corticosteroids are the most widely used treatment modalities. A few cases have been reported using oral corticosteroids.12

The study by Callender described the efficacy of high-potency corticosteroids, such as 0.05% clobetasol propionate and 0.12% betamethasone valerate. An 8-week regimen of clobetasol applied every 12h for 2 weeks, alternating with 2 weeks off, resulted in a 60% reduction in papulopustular lesions and decreased symptoms such as burning, itching, or pain. A mild rebound occurred within the first 2-week cycle. No significant difference was observed when using betamethasone every 12h for 4 week.1,3,15,16 However, there is limited literature supporting its use.

Ogunbiyi and Brahe described the use of triamcinolone acetonide at concentrations ranging from 2.5–5mg/mL up to 40mg/mL. Concentrations>20mg/mL are recommended for lesions>3cm. This treatment is indicated for mild-to-moderate lesions, administered every 4 weeks. Dilution reduces the risk of atrophy, and combining it with lidocaine improves patient comfort.1,3,15

Adotama et al. suggested injecting triamcinolone into the active area with a 1cm margin to include subclinical affected areas (0.1mL of triamcinolone at 5–10mg/mL concentrations with 1cm intervals). This technique improved keloid lesions within 7 weeks and may help prevent lesion development compared with intralesional injection alone. However, side effects such as atrophy, telangiectasias, and hypopigmentation need further monitoring.17

Ogunbiyi has described antibiotic use for superinfections, noting their antimicrobial and anti-inflammatory effects.

Topical antibiotics are considered for mild pustular superinfections. Clindamycin 1% is the most widely used, while other options include erythromycin 2%, benzoyl peroxide, and fusidic acid. These can be combined with steroids or topical retinoids, potentially following acne treatment guidelines.1,18

Oral antibiotics have been reported for moderate-to-severe superinfections. Evidence supports the use of tetracycline, doxycycline, minocycline, trimethoprim–sulfamethoxazole, erythromycin, azithromycin, amoxicillin, and cephalexin.

Tetracyclines are considered the first-line therapy for their anti-inflammatory properties, such as doxycycline at doses of 50–100mg/day twice daily for 12–16 weeks.18 Rifampin, clindamycin, and dapsone have also been used to control superinfections.12 These can be combined with topical and intralesional corticosteroids.1,3,15

Retinoid use is likely based on their efficacy in treating acne vulgaris, given their comedolytic (topical), anti-inflammatory, and follicular occlusion-preventing effects.1,3,15

Topical retinoids include tretinoin 0.025–0.1%, adapalene 0.1–0.3%, and tazarotene 0.05%. Their efficacy depends on concentration, with reported success rates ranging from 35% to 80% in treatments lasting 12–16 weeks.1,3,15,18,19

Oral isotretinoin has been used at doses of 0.25mg/kg per day, showing marked improvement at 6 months. It is recommended when there is no response to treatment with tetracyclines and topical or intralesional corticosteroids.3

Isotretinoin is typically initiated at doses of 0.5–1mg/kg per day, depending on patient tolerance during active phases, and maintained at doses of 0.25–0.4mg/kg per day. The total cumulative dose is 120–150mg/kg, with recurrence rates up to 65%. In severe cases, it may be used alongside oral corticosteroids.1,3,15,18,20

The mechanism of action of imiquimod is related to the stimulation of inflammatory cytokines, inhibition of angiogenesis, and activation of apoptosis, leading to the death of fibroblasts.

Figueroa and Lorenz reported cases in which daily use of imiquimod resulted in clinical improvement of fibrotic papular lesions after 8 weeks.21 In another study, Barr et al. demonstrated the efficacy of imiquimod combined with pimecrolimus over 8 weeks, with no subsequent recurrence.22

The mechanism of action of laser therapy involves the destruction of hair follicles within lesions. It is limited to folliculocentric papular lesions, isolated discrete nodules, or plaques with a vertical height of up to 2–3mm, ensuring greater penetration depth corresponding to hair follicle length.

Umar describes the use of pulsed and long-wave lasers, including 755nm alexandrite, 800nm diode, and Nd:YAG. The latter penetrates deeper (5–7mm) compared with others and is less absorbed by melanin, causing less damage in darker phototypes. Hair follicles are a potential source of new AKN lesions, and their treatment reduces disease progression.23

Alopecia is an expected effect of laser therapy in AKN. Umar proposed a severity-based classification system to predict the area of posterior hairline displacement. The classification ranges from Level I up to IV based on the extent of AKN lesion spread in relation to the occipital notch (Table 3).23

Laser therapy has been proposed as effective for long-term disease control and, together with surgery, is considered for cases where conservative treatments fail or as an adjuvant aftersurgery to prevent recurrence. It can be combined with topical corticosteroids in refractory cases. Laser therapies described for AKN include:

• •

  755nm Alexandrite (12–16J/cm2 fluence, 18mm spot size, 3ms): In the study by Tawfik et al., 6 sessions were conducted at monthly intervals, with greater efficacy observed in papular lesions than in keloids.24

• •

  810–819nm diode: Studies by Maranda and Umar reported efficacy in treating inflammatory and fibrotic papules after the 4th session, with sessions every 1–1.5 months and 90–95% lesion improvement.3,15

• •

  1064nm Nd:YAG (25–35J/cm2 fluence, 10–13mm spot size, 35ms): Effective for darker phototypes, it achieves an 82% reduction in lesion number and size between the 3rd and 6th sessions.15,23,25,26

• •

  2490nm Er:YAG (5Hz, 3mm spot size, 300ms, 800–980mJ pulse energy, partially overlapping mode): Gamil et al. validated Er:YAG laser as an effective, minimally invasive option for early and late AKN lesions, with superior efficacy in advanced lesions vs Nd:YAG.25

• •

  CO2 Laser (10,600nm): Used for surgical excision of plaques and tumor lesions in AKN under local anesthesia. CO2 laser evaporation using a defocused beam with 130–150J/cm2 fluence has been associated with recurrence in some reported cases.3

Its utility is based on the anti-inflammatory, immunosuppressive, and antifibrotic effects of UVB light (290–320nm). Okoge et al. reported its effectiveness in papular lesions with usage 3 times a week for 8–16 weeks. The initial dose was determined by the minimal erythema dose and increased by 20% per session as tolerated, up to week 8 and maintained until week 16. Lesions decreased by 34% and 49% at weeks 8 and 16, respectively, with improved appearance, though less effective compared to laser treatment.15,27

Surgical treatment is recommended for extensive AKN lesions and cases refractory to other treatments. Effectiveness depends on complete removal of hair follicles to prevent recurrence and excision of lesions down to the subcutaneous tissue.

According to Umar's clinical classification of AKN, the sagittal width of lesions relative to the nuchal area predicts esthetic outcomes post-excision (Fig. 5). Lesions with a sagittal width>3cm are more likely to result in wide or dehiscent scars.14,28 The association with dissecting cellulitis and folliculitis decalvans has been linked to wide scars and dehiscence due to the deterioration of tissue laxity.14

Figure 5.

Lateral and posterior views indicating the anatomical references of the nuchal area—upper line demarcated by the occipital protuberance and lower line by the posterior hairline—delineating treatment areas. Figure adapted from Umar et al.28

(0.22MB).

For lesions with a vertical width<3cm, secondary intention healing is preferred. Lesions>3cm sagittal width, located in the lower nape or extending beyond the nuchal area, require tension sutures. Lesions 2.5–3cm sagittal width in the upper nuchal area are ideal for primary closure. After excision and primary closure, trichophytic closure allows hair growth through the scar, resulting in a camouflaged scar.28 Glenn et al. reported a 35% recurrence rate in patients with primary closure or skin grafts.29

Elliptical excision allows for healing within 3 months (6–8 weeks on average), with better contraction and esthetic results compared with pear or semicircular excisions. Recurrence is linked to inadequate excision of affected follicles.29 Umar et al. propose a bat-shaped excision for esthetically acceptable posterior hairlines, recommended for lesions within the nuchal area. No recurrence was observed during 1.9 years of follow-up (Fig. 6).30

Figure 6.

Lateral and posterior views of the head showing reference points for bat-shaped excision alone (a) and with tension sutures. Adapted from Umar et al.30

(0.2MB).

Extensive excision may be considered in patients with large tumor lesions. Staged removal is preferable, as noted by Galarza et al.31 Using negative-pressure wound therapy and split-thickness skin grafting, Labib et al. observed an 80% faster healing rate compared to healing by secondary intention, with complete healing in less than two months. At the 8-month follow-up, no evidence of new lesions was observed.32 Electrosurgery is an option that allows for excision and hemostasis simultaneously, which is similar to CO2 laser excision (130–150J/cm2). With electrosurgery, no recurrence was observed at 8 months, unlike with CO2 laser therapy.3,33

Treatment involving follicular unit extraction, punch, and healing by secondary intention may be considered for papular lesions<5mm (fibrotic papules), with variable efficacy depending on the removal of intralesional hair. In their case report, Umar and Khanna observed improvement after the first session, with remission maintained for 6–12 months after extraction and acceptable esthetic outcomes.34,35

Postoperative therapies may include the use of intralesional or topical corticosteroids, laser therapy, or radiotherapy to prevent recurrence or the appearance of hypertrophic scars (Fig. 7).

Figure 7.

Proposed treatment algorithm for AKN based on stage at clinical presentation.

(0.51MB).

Cryotherapy may be a useful alternative when primary closure is not feasible. Treatment involves 2 cycles of freeze–thaw for 15s (spot freezing).1,3,35

Local radiotherapy is a treatment modality for successfully managing disease refractory to conservative treatments, particularly when surgery and laser therapy are not viable options. Its use at low doses to eliminate intralesional hair not reachable by laser (broad lesions) reduces signs and symptoms of inflammation, with sessions of 2–3Gy at 6MeV over 10–20 sessions. Millán-Cayetano et al. report that total doses of 30Gy do not reach the threshold to cause permanent alopecia (43Gy). By avoiding high radiation doses, complications such as edema, telangiectasias, and skin cancer are minimized. Additionally, tissue remaining after treatment is more likely to respond well to surgery, with fewer complications related to wound healing. However, potential adverse effects must be considered. The estimated risk of skin cancer development by age 70 is 44 per 10,000 cases with a dose of 40Gy.36–38

Lobato-Berezo et al. reported various treatments previously unmentioned, such as photodynamic therapy, JAK inhibitors (baricitinib or tofacitinib), and biological therapies like infliximab and adalimumab. The response to these treatments was mild in 25.75% of cases, moderate in 18.57%, and complete in 37.14%.12