Sebaceous glands are present all over the body except on the palms, the soles and dorsal surfaces of the hand and foot. They are particularly large and numerous on the scalp, the face, the back and the front of the chest. Each sebaceous gland is composed of multiple lobules of epithelial cells. The duct of each lobules converge towards the main sebaceous duct which normally opens into hair follicle (pilosebaceous unit). Only a small number of sebaceous glands open directly on the surface of the skin (the prepuce, labia minora, eyelids, nipples and lips).
The gland’s secretion, sebum, is formed by fatty degeneration of the epithelial cells of the gland. The entire sebaceous cells and its contents are then eliminated into the duct (Holocrine process) and is excreted on to the skin surface through the lumen of the hair follicle. Sebaceous gland activity is under hormonal control. Androgens are the most potent stimulants of seburn production while oestrogens suppress sebaceous gland activity. Seburn contains a complex mixture of lipids i.e., triglycerides, wax esters, squalene, cholestrol ester and cholesterol. The sebum acts as a lubricant and controls moisture loss from the epidermis. Another advantage of sebum is protection of skin from fungal and bacterial infection.
Acne vulgaris is a chronic inflammatory disorder of pilosebaceous unit characterized by the development of comedones, papules, nodules and cysts.
Acne predominantly affects adolescents. The peak incidence is between ages 14 and 16 years in girls and 16 and 19 years in boys.
The basic cause of acne is still unknown. It seems to be a multifactorial disease in which interaction of several factors play an important part in the pathogenesis. The primary event may be (a) obstruction of the sebaceous duct due to alteration in the pattern of keratinization within the follicle, (b) abnormal sebum production with excess quantities or altered composition or (c) increased bacterial colonization (proprionibacterium acnes and staphylococcus epidermidis of pilosebaceous follicles which furnish the lipases responsible for hydrolysis of sebum triglycerides into free fatty acids. All three mechanisms may be involved. Obstruction of duct leads to formation of a comedone, the initial lesion of acne. A comedone can be located either in a closed follicle as a ‘white head’ consisting of lipid and keratin, or in an open follicle as ‘black head’ consisting of keratin and lipid with melanin deposition. The continual accumulation of keratin and lipid may lead to rupture of the follicular wall and release of its contents into the surrounding dermis provoking an inflammatory tissue reaction.
Certain factors such as genetic, climate, stress use of drugs and comedogenic chemicals are known to modify acne.
The disease is characterized by a great variety of lesions which vary from patient to patient but most patients have multiple types of lesions. Various types of lesions are comedones (black or white), papules, pustules, nodules and cysts. There may be post inflammatory Hyperpigementation, The common sites are the face, the upper chest, back and the upper arm. In milder form, the comedones predominate the picture and the pustules are relatively infrequent. In severe form, there is preponderance of inflarnmatory papules, pustules, nodules and cystic lesions. Scarring frequently follows severe type of acne.
Most acne patients have an oily skin with patulous follicular openings. The course of the disease is chronic with frequent remissions and relapses. In majority of the cases, disease tends to subside spontaneously about the age of 25, but may persist indefinitely.
Variants of Acne
Infantile acne is mainly seen in infants and children, characterized by : presence of comedones, papules or pustules on the face.
dominate in this type of acne, and is largely due to excessive squeezing and picking of acne lesions. This is mainly seen in adolescent girls under emotional stress.
There is tendency of acne lesions to flare up in the premenstrual phase.
It is a severe supportive form of acne, characterized by presence of comedones, nodules and cysts with burrowing abscesses and irregular scarring. The lesions are situated chiefly on the back, chest, shoulders and buttocks.
Certain drugs particularly iodides, bromides, INH, corticosteroids, ACTH, androgens and oral contraceptives can produce acne form eruptions.
Many insoluble cutting oils. tars, cosmetics and chlorinated aromatic hydrocarbons can induce acne by external contact.
There are several major approaches to treatment of acne vulgaris including general treatment, topical therapy, systemic therapy and physical modalities.
Oiliness of the skin is best controlled by frequent washing of the face with soap and water and to avoid use of greasy cosmetics. No dietary restrictions should be imposed on the patients, Psychiatric counseling may be required in severe cases of acne with emotional upset. Patients should be advised to avoid further squeezing or manipulation of the lesions.
This is designed to produce peeling of the skin, restore normal keratinization and produce a bactericidal action. Common peeling agents are sulphur (3 5%), resorcin (3 5 %), benzyl peroxide (5 10%) and retinoic acid (0.025 0. 1%). Peeling agents should be applied once or twice a day, taking care to avoid excessive irritation.
Topical antibiotics include erythromycin (1 2%) clindamycin (1 2%) and benzyl peroxide (5 10%). Benzyl peroxide has bacterio static properties in addition to its action as a peeling agent. Comedones may be expressed with a comedo extractor and cyst should be drained and injected with corticosteroids.
The antibiotics such as tetracycline, erythromycin, clindarnycin and cotrirpoxazole are most commonly used in the treatment of acne vul¬garis. Tetracycline is the treatment of choice for moderate to severe: acne and is given in the dosage of 250 mg three to four times daily with a gradual reduction to a maintenance dose of 250 mg once a day for several months, Recently, oral retinoid (isotretinoin) has been found to be very effective drug in the management of severe form of acne, especially nodulo cystic acne and conglobata.
Anti androgens like cyproterone acetate and spironolactone are also beneficial in treatment of acne. Females with recalcitrant and severe type of acne usually require oestrogens either in the form of oral contraceptives or in combination with antiandrogens.
Physical measures include exposure to ultraviolet light, irradiation and exfoliation with carbon dioxide snow (cryotherapy). Dermabrasions may be required for treatment of depressed scars.