Introduction lso known as Acne inversa or the Verneuil's disease, Hidradenitis suppurtiva is a chronic disease with recurrent abscess formation progressing to sinus tracts and resultant scarring. It was first described by Velpeau in 1839during his study involving the origin of abscess involving the sebaceous follicles in axillae [1] It is commonly seen in females and also incidence involving the axilla in both sexes is nearly equal. Commonly seen in adolescents, it initially presents like a comedo and progresses with mucopurulent discharge eventually leading to scarring. # II. # Epidemiology ? Prevalence: 1 in 300 adults Stage 3: Diffuse or broad involvement across a regional area with multiple inter-connected sinus tracts and abscesses. Significant scarring is seen and fistula formation is present. IV. # Imaging Imaging evaluation is initially indicated to evaluate the extent and the feasibility to obtain image guided aspirate for culture and sensitivity. A simple ultrasound guided aspiration of the involved part can be used to obtain sample for culture and sensitivity if secondary infections are suspected when there is no sinus tract to directly obtain swabs. [3] MRI is the preferred modality for evaluating the extent of disease as well as follow up. V. # MRI Spectrum The protocol The MRI of the involved area is best suited to evaluate the extent of disease and also may help in monitoring treatment response. The MRI findings parallel with the clinical features therefore avoiding any clinical confusion. STIR (Short tau inversion recovery) and T2W sequences are recommended protocol. It may initially just show thickening of the skin and subcutaneous tissue which soon progresses to induration best seen on routine T2W and STIR images as subdermal hyperintense signal extending upto skin. In a few days there is formation of subcutaneous abscesses however the disease is confined to the skin and subcutaneous tissue. Rarely there is fistulous communication with bladder urethra or rectum etc. in patients with highly virulent infection or compromised immune status like diabetes. Reactive inguinal lymph nodes are also seen in conjunction. Post treatment cases demonstrate residual scarring as STIR hypointense tracts. (Refer figure D) VI. # Differential Diagnosis Carbuncles, Lymphadenitis, Infected Bartholin's cyst, sebaceous cysts, Cellulitis/ erysipelas, Lumbosacral epidural abscess are few of the common differential diagnosis which can be easily ruled out combining the imaging and the clinical picture. [4] VII. # Sequelae Various sequel can be strictures, disfiguring edema, arthropathy and chronic cases may undergo metaplasia and even lead to squamous cell carcinoma. # VIII. # Treatment Treatment of HS is directed according to disease severity. Aim is to alleviate symptoms and improve quality of life. Many a times combination therapy is resorted. a) Anti-inflammatory Agent [5] ? Intralesional steroids: Triamcinolone acetonide 2-5mg/ml can be used for few lesions ? Anakinra: An IL-1 inhibitor (100mg SC/day for 12 weeks) showed reduction in severity of disease ? Antibiotics: Many topical and oral antibiotics like clindamycin(1%;300mg BD), tetracycline, rifampicin(300mg BD); have been used alone or in combination for their anti-inflammatory and immunomodulatory properties. [6] A study of hyperbaric oxygen therapy with antibiotic combination showed good improvement in sartorius and DLQI score. [7] Antiandrogens: Although anecdotal in females, a double blinded study in women with Cyproterone acetate(100mg) and Ethinyl estradiol(50 micrograms) as per reversed sequential therapy laid down by Hammerstein and Cupceancu, showed reduced discharge and swelling. [8] Finasteride(5-10 mg/day) used primarily for prostate cancer showed good results in pediatric patients. [9] # b) Retinoids Isotretinoin worked in patients with mild disease when given in low doses 0.5-1.2 mg/kg/day over 4 to 12 months. [10] A study of Acitretin (0.6mg/kg/day) over 6 to 12 in 12 patients with moderate to severe disease showed improvement. [11] The mechanism of action is through the keratolytic action thereby reducing ductal occlusions. # c) Immunosuppresive therapy Cyclosporine (4.5mg/kg/day) showed raid relief in resistant cases to antibiotics and UVB therapy. [12] TNF? inhibitors have been proven to be quite effective in Hurley's II and III stages of the disease. Infliximab 5mg/kg IV at week 0, 2 and 6 were given to 33 patients; drug was well tolerated and showed good improvement in symptoms and severity of the disease. [13] Etanercept showed varied results when administered twice weekly 50mg for 12 weeks. Adalimumab when given weekly instead of fortnightly showed superior results when 4 randomized control trials were analysed. [14,15] Apremilast a selective phosphodiesterase 4 inhibitor (30 mg BD); used primarily for psoriasis; showed moderate results. [16] # d) Miscellaneous Botulinum toxin reduces acetylcholine release and in turn reduces the sympathetic activation of apocrine glands. A dose of 40 to 50 Units per session for 3 to 4 times over 3 years reported remission in 4 cases. [17,18] Metformin helps in decreasing androgen sensitivity by lowering circulating insulin and helps in managing the metabolic syndrome associated with disease. [19] Others: Zinc, Cryotherapy and Photodynamic therapy e) Surgical Intervention This is the last resort to unresponsive cases. Deroofing is most effective in combination with antibiotics and anti-inflammatory. [20] f) Laser therapy Nd: YAG laser in 22 patients showed significant improvement in all (65%), axilla (62%), Inguinal (53%), Inframammary (51%). [21] Carbon dioxide laser for lesions to heal by secondary intention has also been tried. [ ![MRI will show loculated T2W and STIR hyperintense pockets of collection with mild post contrast rim enhancement. This correlates to Stage 1 of clinical classification. (Refer figure A) This may either heal by mild scarring or progress towards chronic skin involvement in the form of multiple raised subdermal pockets of pus which ultimately rupture to form sinus tract. (Refer figure B) This correlates to Stage 2 of clinical classification. The stage 3 of clinical classification is includes extensive local involvement in terms of area as well as severity and often includes refractory cases with multiple interconnecting sinus tracts. The chronicity can be identified by thick walls of the sinus tract appearing hypointense on STIR due to scarring.(Refer figure C)](image-2.png "") ![Figures and Legends](image-3.png "") B![Figure B: Hurley Stage 2 MRI of the perineum: Coronal STIR image shows evolution of the abscess into a linear hyperintense tract/ sinus formation.](image-4.png "Figure B :") 3D![Figure C: Hurley Stage 3.MRI of the perineum:Coronal STIR image from the selected slices shows evolution of the abscess into a linear hyperintense tract/ sinus formation. Due to chronicity of the sinus, the tract appears more fibrosed and hypointense.](image-5.png "Figure C: Hurley Stage 3 .Figure D :") Clinical Classification: Hurley stages-3 well delineatedstages have been described by Hurley emphasizing theclinical diagnosis.Stage 1:? Sex predilection: Females > Males? Onset: Adolescent to middle age? Family history: Positive family history with anautosomal-dominant mode of inheritance? Associations: Crohn's disease, Dowling Dego's,Arthropathy (SAPHO), Smoking, Obesity, Hormonalinfluence [2]III.pathophysiology Hidradenitis Suppurativa-The Imaging Spectrum © 2020 Global Journals * Hidradenitis suppurativa: a review MCWiseman Dermatol Ther 17 2004 * Hidradenitis suppurativa: pathogenesis and management DESlade BWPowell PSMortimer Br J Plast Surg 56 2003 * MRI features of hidradenitis suppurativa and review of the literature AMKelly PCronin AJR Am J Roentgenol 185 5 2005 * The differential diagnosis and comorbidity of hidradenitis suppurativa and perianal Crohn's disease JMChurch VWFazio ICLavery JROakley JWMilsom * Hidradenitis suppurativa: A systematic review and meta-analysis of therapeautic interventions HTchero CHerlin FBekara SFluieraru Indian J Dermatol Venerol Leprol 85 2019 * Topical treatment of hidradenitis suppurativa with clindamycin OJClemmensen Int J Dermatol 22 1983 * Karabudak Abuaf O. A prospective randomized controlled trial assessing the efficacy of adjunctive hyperbaric oxygen therapy in treatment of hidradenitis suppurativa HYildiz LSenol EErcan MEBilgili Int J Dermatol 55 2016 * Control of Hidradenitis suppurativa in women with combined antiandrogen and oestrogen therapy RSSawers VARandall FJEbling Br J Dermatol 115 1986 * Finasteride for the treatment of hidradenitis suppurativa in children and adolescents HKRandhawa JHamilton EPope JAMA Dermatology 149 6 2013 * Long-term results of isotretinoin in the treatment of 68 patients with hidradenitis suppurativa JBoer MJVan Gemert J Am Acad Dermatol 40 1999 * Long term results of acitretin therapy for Hidradenitis suppurativa. Is Acne-inversa a misnomer? JBoer MNazari Br J Dermatol 164 1 2011 * Cyclosporin-responsive hidradenitis suppurativa DABuckley SRogers J R Soc Med 88 1995 * Treatment of hidradenitis suppurativa with etarnacept injection DRAdams JAYankura ACFogelberg AndersonBe Arch Dermatol 146 2010 * Adalimumab treatment in women with moderate to severe hidradenitis suupurativa from the placebo-controlled portion of a phase 2, randomized, doble-blind study AGottlieb AMenter AArmstrong COcampo YGu HDTeixeira J Drugs Dermatol 15 2016 * Two phase 3 trials of adalimumab for hidradenitis ssupurativa ABKimball MMOkun DAWilliams ABGottlieb KAPapp CCZouboulis N Eng J Med 375 2016 * Apremilast in the treatment of moderate to severe hidradenitis suppurativa: A case series of 9 patients PWeber SeyedJafari SMYawalkar NHunger RE J Am Acad Dermatol 76 2017 * Prepubertal hidradenitis suppurativa successfully treated with botulinum toxin A MFieto-Rodriguez ESendagorta-Cudos PHerranz-Pinto RDe Lucas-Laguna Dermatol Surg 35 2009 * Hidradenitis suppurativa treated with clostridium botulinum toxin A ABKhoo EPBurova Clin Exp Dermatol 39 2014 * Longstanding Hidradenitis suppurativa treated effectively with metformin BArun ALoffeld Clinical and Exp Dermatology 34 8 2009 * Deroofing: A tissue saving surgical technique for the treatment of mild to moderate hidradenitis suppurativa lesions HHVan Der Zee EPPrens JBoer J Am Acad Dermatol 63 2010 * Radomized control trial for the treatment of hidradenitis suppurativa with Nd YAG laser ETierney BHMahmoud CHexsel DOzog IHamzavi Dermatol Surg 35 2009 * Treatment of hidradenitis suppurativa withcarbon dioxide laser excision and second intention healing EMFinley JLRatz J Am Acad Dermatol 34 1996