Overview

Definition

Hidradenitis suppurativa (HS), also referred to as acne inversa, is a chronic inflammatory skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin condition due to occlusion of apocrine sweat glands and hair follicles.

Epidemiology

• Prevalence of HS is approximately 1%–4% globally.
• 3 times more common in women than men
• Usual age of onset is 12–40 years.
• Rarely seen in children before puberty Puberty Puberty is a complex series of physical, psychosocial, and cognitive transitions usually experienced by adolescents (11-19 years of age). Puberty is marked by a growth in stature and the development of secondary sexual characteristics, achievement of fertility, and changes in most body systems. Puberty
• More common in the African American population

Etiology

Hidradenitis suppurativa develops due to blockage of hair follicles and the ducts of sweat glands in the skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin. Risk factors include:

• Smoking
• Obesity Obesity Obesity is a condition associated with excess body weight, specifically with the deposition of excessive adipose tissue. Obesity is considered a global epidemic. Major influences come from the western diet and sedentary lifestyles, but the exact mechanisms likely include a mixture of genetic and environmental factors. Obesity
• Genetic susceptibility: Approximately 40% of patients have a positive family history.
• Mechanical stress (friction caused by wearing tight clothes)
• Hormonal changes: ↑ severity during the perimenstrual period in women
• Medications:
  • Medroxyprogesterone acetate
  • Levonorgestrel intrauterine device
  • Lithium

Pathophysiology

Normal physiology

The skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin is mainly composed of 3 layers:

• Epidermis (outer layer):
  • Serves as a barrier, protects from infections
  • Helps in tactile sensation
• Dermis (middle layer): contains blood vessels, nerves, hair follicles, and sebaceous and sweat glands
• Hypodermis (inner layer): contains fat and connective tissue Connective tissue Connective tissues originate from embryonic mesenchyme and are present throughout the body except inside the brain and spinal cord. The main function of connective tissues is to provide structural support to organs. Connective tissues consist of cells and an extracellular matrix. Connective Tissue

Pathophysiology of HS

The exact pathogenesis of HS remains unclear; the initial event in the development of HS is follicular occlusion.

• Apocrine exocrine glands secrete sweat into hair follicles in the dermis.
• Ductal keratinocytes proliferate, incited by:
  • Excessive hormonal stimulation 
  • Nicotine/smoke
• Accumulated keratin debris → immune reaction → folliculitis and follicular blockage
• Keratinocytes cause mechanical plugging. 
• Pilosebaceous structures rupture → 
  • Release of keratin fragments, hair, and sebum
  • Inflammatory cells accumulate.
• Repeated acute reactions result in chronic granulomatous inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body's defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation and suppuration secondary to bacterial proliferation.

Clinical Presentation

The primary sites of involvement for HS are the intertriginous skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin areas of the axillary, groin, perianal, perineal, and inframammary regions, though HS can occur in any skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin area that contains FPSUs.

• Symptoms:
  • Painful recurrent skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin lesions present as tender erythematous nodules.
  • Pustules or abscesses
  • Draining skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin sinuses
• Complications:
  • Scarring of the skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin
  • Contractures
  • Fistulas in the anogenital region
  • Rarely, squamous cell carcinoma Squamous cell carcinoma Cutaneous squamous cell carcinoma (cSCC) is caused by malignant proliferation of atypical keratinocytes. This condition is the 2nd most common skin malignancy and usually affects sun-exposed areas of fair-skinned patients. The cancer presents as a firm, erythematous, keratotic plaque or papule. Squamous Cell Carcinoma

Diagnosis

The diagnosis is based on a clinical exam. A history of the pattern of disease with recurrent deep skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin abscesses and poor response to antibiotics is specific for HS.

• Clinical staging Staging Cancer is the 2nd leading cause of death in the US after cardiovascular disease. Many malignancies are treatable or curable, but some may recur. Thus, all malignancies must be assigned a grade and stage in order to guide management and determine prognosis. Grading, Staging, and Metastasis:
  • Stage I: 
    • Abscess formation 
    • No sinus tracts of scarring
  • Stage II: 
    • Recurrent abscesses
    • Single or multiple widely separated lesions with sinus tracts and scarring
  • Stage III: 
    • Diffuse involvement
    • Multiple sinus tracts and abscesses 
• Laboratory studies: 
  • Culture of superficial HS lesions for bacterial superinfection
  • Skin biopsy: only if diagnosis is unclear or to exclude other diseases
• Imaging: not necessary, but MRI can be helpful to diagnose HS of anogenital region specifically

Management

The key to management is early diagnosis and treatment.

• Conservative treatment:
  • Lifestyle modification: 
    • Weight loss
    • Smoking cessation
  • Warm compresses for painful skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin lesions (dry better than wet)
• Medical management:
  • Antibiotics:
    • Clindamycin (both oral and topical)
    • Tetracyclines Tetracyclines Tetracyclines are a class of broad-spectrum antibiotics indicated for a wide variety of bacterial infections. These medications bind the 30S ribosomal subunit to inhibit protein synthesis of bacteria. Tetracyclines cover gram-positive and gram-negative organisms, as well as atypical bacteria such as chlamydia, mycoplasma, spirochetes, and even protozoa. Tetracyclines (doxycycline)
    • Amoxicillin/clavulanate
  • Retinoids: Isotretinoin is helpful.
  • Immunosuppressants Immunosuppressants Immunosuppressants are a class of drugs widely used in the management of autoimmune conditions and organ transplant rejection. The general effect is dampening of the immune response. Immunosuppressants/ tumor necrosis factor Tumor necrosis factor Tumor necrosis factor (TNF) is a major cytokine, released primarily by macrophages in response to stimuli. The presence of microbial products and dead cells and injury are among the stimulating factors. This protein belongs to the TNF superfamily, a group of ligands and receptors performing functions in inflammatory response, morphogenesis, and cell proliferation. Tumor Necrosis Factor (TNF) alpha (TNFα) blockers:
    • Adalimumab
    • Infliximab 
    • Cyclosporine
• Surgical management for resistant disease:
  • Incision and drainage
  • Laying open of sinus tracts
  • Radial excision

Differential Diagnosis

• Carbuncles: a deeper skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin infection involving hair follicles. Lesions present as painful, pus-filled, inflamed nodules on the skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin. Carbuncles are commonly present in the back of the neck, shoulders, hips, and thighs due to higher friction and sweat production. Staphylococcus Staphylococcus Staphylococcus is a medically important genera of Gram-positive, aerobic cocci. These bacteria form clusters resembling grapes on culture plates. Staphylococci are ubiquitous for humans, and many strains compose the normal skin flora. Staphylococcus aureus is the main bacteria Bacteria Bacteria are prokaryotic single-celled microorganisms that are metabolically active and divide by binary fission. Some of these organisms play a significant role in the pathogenesis of diseases. Bacteriology: Overview causing infection. Patients may have a fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever. An infected carbuncle may resolve on its own with warm compresses or may require antibiotics.
• Lymphadenitis: an infection of lymph nodes presenting as tender, enlarged nodes that may be acute or chronic. Causes include bacterial and viral infection. The diagnosis requires a detailed history and examination. The most common cause of bilateral cervical adenitis is viral upper respiratory tract infection; tuberculosis Tuberculosis Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis complex bacteria. The bacteria usually attack the lungs but can also damage other parts of the body. Approximately 30% of people around the world are infected with this pathogen, with the majority harboring a latent infection. Tuberculosis spreads through the air when a person with active pulmonary infection coughs or sneezes. Tuberculosis is a consideration as well. For chronic cases, lab testing with CBC, erythrocyte sedimentation rate (ESR), culture, and serologic testing is recommended. Management is based on the underlying cause.
• Acne vulgaris Acne vulgaris Acne vulgaris, also known as acne, is a common disorder of the pilosebaceous units in adolescents and young adults. The condition occurs due to follicular hyperkeratinization, excess sebum production, follicular colonization by Cutibacterium acnes, and inflammation. Acne Vulgaris: a common skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin disorder characterized by the formation of papules, pustules, nodules, and/or cysts due to the inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body's defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation of pilosebaceous units. Acne vulgaris Acne vulgaris Acne vulgaris, also known as acne, is a common disorder of the pilosebaceous units in adolescents and young adults. The condition occurs due to follicular hyperkeratinization, excess sebum production, follicular colonization by Cutibacterium acnes, and inflammation. Acne Vulgaris can be mild or moderate-to-severe in presentation. The disorder may result in depression and anxiety in patients. The treatment includes counseling of patients along with antibiotics, retinoids (oral and topical), oral contraceptives, benzoyl peroxide, salicylic acid, and dapsone.
• Pilonidal disease: a suppurative condition of the skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin and subcutaneous tissue resulting in intermittent bloody pus-filled discharge. Pilonidal disease can present as an abscess or draining sinus tracts. Diagnosis is mainly clinical. Excision is the standard definitive treatment of choice, and the recurrence rate is high. Risk factors include trauma, obesity, deep natal cleft, and positive family history. Antibiotics can be used in the presence of cellulitis Cellulitis Cellulitis is a common infection caused by bacteria that affects the dermis and subcutaneous tissue of the skin. It is frequently caused by Staphylococcus aureus and Streptococcus pyogenes. The skin infection presents as an erythematous and edematous area with warmth and tenderness. Cellulitis, and surgery may be needed later for recurrent complicated lesions.