Intralesional and intramuscular triamcinolone is frequently employed in the treatment of various inflammatory, fibrohistiocytic, and autoimmune skin diseases including keloids, alopecia areata, nodulocystic acne, granuloma annulare, psoriasis, and more [11, 25]. While uncommonly used in outpatient dermatology, ultrasound is a non-invasive, and cost-effective imaging tool that has diagnostic and therapeutic purposes for infundibular cysts, lipomas, pilomatricomas, hemangiomas, systemic sclerosis, morphea, as well as hair and nail disorders [26].

Currently, the recommendation for employing triamcinolone injections in the management of HS is primarily derived from consensus, expert opinion, case studies, or disease-oriented evidence, with patient-oriented evidence of limited quality, corresponding to Level of Evidence II [8]. A previous systematic review conducted by Cuenca-Barrales et al.22 regarding ILTAC in HS found it to be effective for both acute and chronic inflammatory lesions with mild adverse effects. We expanded upon their search and specifically explored the efficacy of triamcinolone injections, encompassing both intralesional and intramuscular administration methods, as well as comparing ultrasound-guided and non-ultrasound-guided injections.

In the setting of acute HS, multiple studies associated with intralesional triamcinolone therapy supported its use [14,15,16]. Garelik et al. [16] showed that the majority of patients were satisfied or very satisfied with high-dose ILTAC-20 or 40, while Riis et al. showed reduced inflammation of lesions with ILTAC-10, regardless of the amount injected and suggested that the dose of triamcinolone could be reduced without sacrificing therapeutic effect. However, it should be noted that this study did not address lesion size, as larger lesions may require a higher dose of triamcinolone and the study was limited by a lack of control group. Cuenca-Barrales et al. [14] described the effectiveness of ILTAC-10, but reported that a type I diabetic patient experienced hyperglycemic decompensation, underscoring the potential, though very unlikely metabolic effect of this treatment.. This study was published as an abstract and insufficient information on the causality between ILTAC-10 administration and glycemic decompensation was provided. From clinical experience, when ILTAC-40 is given for acute HS flares, side effects are rare when administered with proper technique and more significant clinical improvement is observed (Fig. 2).

Female diagnosed with HS in mid-30 s who received 1 mL of triamcinolone (0.25 mL in each quadrant) 40 mg/mL and followed up one month. (a) Three tender, inflammatory nodules on right axilla that was injected with ILTAC-40 (b) One month status-post ILTAC-40 with decreased pain, size, and erythema noted at sites of previous lesions

In contrast, one RCT [12] did not find a statistically significant difference between 0.1 mL of NS, ILTAC-10, and ILTAC-40 for the treatment of acute HS lesions. Fajgenbaum et al.’s [12] study did not entirely address lesion size, with no lesion larger than 2 cm (cm) in size. Despite no statistical significance between the interventions, all were found to be “a little bit helpful” to “moderately helpful,” suggesting that the act of puncturing a lesion or injecting external solution improves symptoms. A sample size of 58 lesions studied from 32 individual subjects limits this study’s generalizability. In Saunte et al.’s [27] response to this study, it was suggested that using one to four mg of triamcinolone was an insufficient dose to treat active lesions. Our study supports this notion as all the reports included in this review besides Fajgenbaum et al. have shown the therapeutic effect of triamcinolone at higher dosages of 20 mg/mL to 40 mg/mL [13,14,15,16,17, 19,20,21,22,23].

When there are multiple HS lesions affecting more than 2 noncontiguous anatomic regions of the body, administration of triamcinolone into each individual lesion is quite impractical. The use of IMTAC and TTI are two off-label alternative treatment strategies that may be utilized for widespread and/or severe HS lesions.

Benesh et al. [13] showed that IMTAC is a safe, effective, and well-tolerated option for treating acute and extensive flares of HS. The study reported a reduction in HS severity, improvement in inflammation and pain scores, and positive patient feedback. The high efficacy of IMTAC may be associated with its prolonged duration of action [28]. One caveat to avoid hypothalamic–pituitary–adrenal (HPA) axis suppression, is restricting the interval between two doses of 40 mg/mL of triamcinolone to 12-weeks. In order to optimize treatment, the dose of triamcinolone should be adjusted according to the patient’s weight [13]. The recommended dosage is 1.1–1.4 mg of triamcinolone per kilogram (Fig. 3).

HS lesion size and corresponding volume of ILTAC-40 to be administered [13, 16]. (Permission to use figure granted from SAGE Publishing)

Similarly, Dautriche et al. [24] demonstrated efficacy of TTI in the treatment of refractory HS after failing multiple standard therapies. The authors postulated that the delivery of triamcinolone into the dermis and superficial fascia forms a long-acting reservoir that passes through fibrous tissue, ultimately distributing to the follicle and the surrounding area. In this case, conscious sedation was required for TTI, precluding its applicability in an outpatient setting lacking an anesthesia specialist. Larger studies utilizing this method in adult patient populations are needed before it can be recommended as a standard treatment option.

All studies of ultrasound-assisted ILTAC reported significant regression of abscesses and fistulous tracts. This is likely due to the fact that high frequency cutaneous ultrasound (HFUS) can detect lesions less than 0.1 mm [20, 21]. Furthermore, the use of ultrasound guided infiltrations aided precise needle placement for delivery of triamcinolone [17, 18, 22].

Garcia-Martinez et al. [20] reported the utility of triamcinolone in treating both acute and recalcitrant HS lesions. Iannone et al. [21] found that ILTAC-20 was optimal for acute lesions. This was corroborated by Garelik et al. [16] in non-ultrasound assisted treatment. Caposiena Caro et al. [19] observed decreased clinical responses in cases with wider sinuses or higher fibrotic scarring, They recommended more frequent injections for these morphologies. Echoing this sentiment, when Sechi et al. [22] utilized ultrasound to assess the degree of fibrosis in draining fistulas, ILTAC therapy resulted in significant reductions of fibrotic scarring and decreased reliance on surgical intervention. Similarly, Salvador-Rodriguez et al. [17] further emphasized the importance of baseline ultrasound evaluations to guide treatments.

Collectively, these studies advocate for the integration of ultrasound evaluation in HS treatment. Ultrasound can accurately assess the size and extent of HS lesions pre-treatment, enabling better identification of subclinical lesions like abscesses and enhancing visualization of needle entry into target tissue compared to delivery via clinical examination alone [29]. Distinctive features can be visualized through ultrasound that cannot be seen clinically such as increased dermal thickness, abnormal hair follicles, and non-fibrotic scarring fistulas, ultimately aiding in both diagnosis and disease monitoring [20, 22, 30]. Nonetheless, it is important to acknowledge the limited training and use of ultrasound in dermatology. One survey reported that 1% of dermatologists used ultrasound in practice [31]. The lack of training, coupled with limitations in ultrasound technology as well as variations in body habitus that affect acoustic properties pose significant barriers to widespread implementation of ultrasound in dermatological practices [32].

The most common side effects reported with intralesional injection of triamcinolone include injection site pain, erythema, irritation, skin atrophy, hypo- and hyperpigmentation. The highest risk of side effects is associated with anatomic location (especially breast and groin) and appears to be dose-dependent [22]. These findings have been reported in multiple studies [13, 19, 20, 23]. Dose-dependent changes in skin pigmentation and atrophy likely result from the antiproliferative action of triamcinolone on keratinocytes, fibroblasts, and melanocytes, causing altered collagen metabolism and melanin synthesis [33]. While systemic absorption is relatively minor with subcutaneous triamcinolone, glycemic effects associated with diabetes mellitus is possible [14, 17]. Additional complications, such as fever, delayed menstrual cycle, and psychiatric symptoms have been reported in a few studies [17, 18].

Intralesional and intramuscular corticosteroid injections have been used to treat many dermatologic and non-dermatologic conditions. In virtually all settings, ILTAC treatments are associated with both local and systemic side effects. Hypo/hyperpigmentation, dermal or subcutaneous atrophy, alopecia, infection, ulceration, and localized dystrophic calcification are uncommon complications [34]. Intramuscular injection of corticosteroids, in particular, has the potential to cause nerve injury, as well as dermal, subcutaneous, and/or muscle atrophy [35]. While rare compared to systemic corticosteroids, intralesional and subcutaneous corticosteroid injections have been associated with systemic side-effects including but not limited to iatrogenic Cushing syndrome, decreased bone density, immunosuppression, hyperglycemia, hormonal changes, mania, and HPA axis suppression [36]. It is noteworthy that a prospective study investigating the systemic effects of 40 to 200 mg of ILTAC for subglottic stenosis revealed HPA axis suppression was short-lived and normalized within a week [37]. This suggests that long-term systemic effects are unlikely. The safety of ILTAC therapy may be inferred from our study of 549 participants examined across 13 studies revealing only 23 patients experienced adverse effects.

A major limitation of all studies reviewed is the absence of uniform volume and concentration adjustments based on lesion size. From clinical experience, it is likely a five cm inflammatory nodule requires a higher volume of triamcinolone than a one cm nodule. Otherwise, many of the prospective studies were limited by small sample sizes, lack of a control group, and short follow-up periods. Most studies failed to address lesion size and anatomic location. By comparison, the retrospective studies were limited by non-standardized therapy, incomplete data, and were more prone to recall and selection bias. Additionally, Fajgenbaum et al. [12] noted in their RCT, the number and volume of injections administered might not accurately represent standard clinical practice, potentially constraining the generalizability of their findings. The inclusion of data from ultrasound-guided studies of ILTAC may have strengthened outcome measures regarding overall efficacy of ILTAC in our review and is not used in daily practice. Several limitations of our review include the heterogeneity of methods and outcomes across all studies (Table 1). This was most problematic when Hurley stage classifications and concurrent treatments were omitted. Nonetheless, the utility ILTAC therapy for HS was supported by the findings of all studies except Fajgenbaum et al. [12].

We outlined general, concise treatment recommendations of triamcinolone injections with the dosages depending on the experience and discretion of the clinician. (Table 2) Recommendations were stratified by International Hidradenitis Suppurativa Severity Score System (IHS4) with one point given for nodules, two points for abscesses, and four points for fistulas/sinus tracts. As most dermatologists do not routinely use ultrasound in their daily practice, the recommendations given are for non-ultrasound guided triamcinolone injections to treat HS flares. The sole study in this systematic review that commented on volume of triamcinolone injections based on lesion size was Benesh et al. [13] (Fig. 3).