Certain unique terms are used to describe skin rashes and lesions. Skin lesions may be classified into primary (unaltered) or secondary (altered) skin lesions. Learning about the specific terminology of skin rashes can be advantageous both for the non-dermatologist doctors and the patients.
What is a Primary Skin Rash?
Primary skin lesions are the initial lesions which are unaltered by scratching, rubbing, and application of creams or those which have not undergone natural regression over time. Following are the main primary skin lesions:
- Macule. A macule is a flat, circumscribed skin rash without any elevation or depression and measuring under 1 cm in size. Examples of macules are freckles, small tattoos, vitiligo, Café au lait etc.
- Patch. A macule larger than 1 cm is called a patch. Vitiligo, melasma, certain non-raised birthmarks etc. present as patches of different colors on the skin.
- Papule. A papule is an elevated, solid bump measuring less than 0.5 cm in size. Skin tags, lichen planus, molluscum contagiosum, raised moles are all examples of papules. A combination of macules and papules, a maculopapular rash may appear in certain infections likes measles or scarlet fever and also as an allergic drug eruption following ingestion of certain medications like amoxicillin.
- Plaque. Plaque is an elevated, solid, coalesced papule, more than 0.5 cm in size. Psoriasis, mycosis fungoides, ring worm, eczema, Bowen’s disease are some of the skin diseases presenting with plaques.
- Vesicle. A vesicle is a small blister, less than 0.5 cm in size, and, contains a clear fluid within. Herpes simplex (cold sores), herpes zoster and pompholyx are classical examples of vesicular eruptions.
- Bulla (Pl.Bullae). Bulla is a large vesicle, more than 0.5 cm in size. Bullae or blisters are characteristic skin lesions in diseases like pemphigus vulgaris, bullous pemphigoid and bullous impetigo.
- Pustule. Pustule can be defined as an infected papule or vesicle containing pus inside, the result of inflammation causing destruction of the germs and the tissue cells.
- Comedo. A comedos is the primary lesion seen in acne and it is the result of a collection of sebum and keratin plugging in the hair follicle. Open comedones are popularly known as blackheads and closed comedones, whiteheads.
- Nodule. A nodule is similar to a papule, but with a deep constituent. Most of the nodules are visible as slight elevations on the skin surface, but some can only be felt underneath the skin. Erythema nodosum, rheumatoid nodules, lipoma and metastatic carcinoma are a few examples of nodular swellings.
- Cyst. A cyst is a nodule that contains fluid or semi-liquid material. Severe acne can present as nodules and cysts. Interestingly, acne is one disease in which most of the primary skin lesions can occur at one or the other time: comedones, papules, pustules, nodules and cysts are different manifestations of acne. Sebaceous cysts, epidermoid cysts and pilar cysts are some of the other examples of cystic skin swellings.
- Wheal. Wheals are hives; the transient, firm, itchy elevations on the skin commonly seen in urticaria, dermographism and urticaria pigmentosa.
What is a Secondary Skin Lesion?
Scratching, scrubbing or superadded infection to a primary lesion or normal skin results in secondary skin lesions. Following are the main secondary skin lesions:
- Crust. A vesicle, bulla or pustule becomes dried up to form a crust or a scab. This is a collection of dried serum, blood and cellular remnants of inflammation and infection.
- Erosion. Erosion is caused by small abrasions on the skin, with minimal loss of the surface. These usually heal without any scarring.
- Ulcer. Ulcers are full thickness loss of skin and heal with scarring. These are the result of infected wounds or loss of tissue due to decreased blood flow or injury, as occurs in diabetic patients.
- Fissure. Fissures are painful cracks in the skin with well defined walls.
- Excoriation. These are linear erosions caused by scratching, a common occurrence in teenagers suffering from acne. Constant excoriations could lead to scarring and pigmentation.
- Scar. Scar tissue is a collection of connective tissue which is the aftermath of damage to the deeper layers of the skin.
- Scale. Thickening of the outer layer of the skin results in scales. Usually seen in psoriasis, pityriasis versicolor, pityriasis rosea etc.
The unique terminologies of dermatology are worth a study by everyone. It will come handy when you consult a doctor for a skin problem, describe your skin rash in a skin forum or over phone and while reading articles on skin diseases on the web, textbooks and journals.
What are the Primary and Secondary Skin Rashes: Related Article
Source:
- Fitzpatrick JE & Aeling JL. Dermatology Secrets. Mosby Publishers, 1996.
Hanish Babu - Dr.Hanish Babu, MD is a dermatologist and a feature writer on Suite101.com with more than 200 articles related to skin diseases on the ...
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