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Dermatology

Essentials of Dermatology for the Primary Care Provider: Part II

Volume 55 - Issue 11 - November 2015

ABSTRACT: Skin diseases are among the most frequently encountered conditions in primary care. This article reviews the etiology, pathophysiology, and clinical characteristics, as well as outlines management approaches for common dermatologic conditions. Part 1 focused on facial dermatitides and common generalized eruptions. This second part of the series focuses on common cutaneous infections and systemic diseases, as well as the use of topical corticosteroids.

KEYWORDS: Dermatology, skin, systemic diseases, cutaneous infections, fungal infections, topical corticosteroids.

Skin concerns, from rashes to bumps, can trouble patients and perplex practitioners. As many as 1 in 3 patients presenting to their primary care doctor have at least one skin problem.1 The first part of the series focused on facial dermatitides (eg, acne vulgaris, rosacea, seborrheic dermatitis, eyelid dermatitis) and common generalized eruptions (eg, eczema, psoriasis)—reviewing common dermatologic diseases, with a focus on differentiating entities and detailing treatment options for multiple conditions to help guide practitioners through the world of cutaneous disease. The second part of this series focuses on the use of topical corticosteroids as well as common cutaneous infections and systemic diseases.

Note: Many of the treatments discussed in the article are not FDA approved for the indication used and represent off-label use.

Common Cutaneous Infections

Table 1 provides an overview of cutaneous infections, with specific entities discussed in greater depth below.  

Bacterial Infections

Bacterial skin infections range from folliculitis to cellulitis and are common complaints in primary care. Bacterial infections may be preceded by trauma or may occur without an obvious inciting event. Staphylococcus aureus and Streptococcus pyogenes are the major causes of cutaneous bacterial infections, with a range of clinical presentations from impetigo—a common, contagious, superficial skin infection—to sepsis and, rarely, toxic shock syndrome. In superficial skin infection, culture of purulent material is helpful in determining the organism and antibacterial sensitivities, which can guide treatment decisions.

Bacterial folliculitis occurs frequently and is a superficial or deep infection of the hair follicle.2 Bacterial folliculitis should be distinguished from Malassezia (Pityrosporum) folliculitis, which generally presents in young adults as pruritic follicular-based papules and occasionally as pustules on the back, chest, and shoulders. The central white-yellow color often represents compact keratin rather than pus, which is seen in bacterial folliculitis. Topical antifungal shampoos and creams can be helpful, and, in resistant cases, oral fluconazole or itraconazole should be administered.

Cellulitis, a soft-tissue infection of the deep dermis and subcutaneous tissue, manifests as areas of erythema, tenderness, warmth, and swelling, often with systemic symptoms of fever, chills, and malaise. The borders are ill-defined; in severe infections, bullae and pustules may develop. The most common causes are group A streptococcus or S aureus. Cellulitis, however, has many mimics, called “pseudocellulitis,” including insect bites, gout, thrombophlebitis, panniculitis, lipodermatosclerosis, and allergic contact dermatitis.

Fungal Infections 

Superficial fungal infections caused by Candida species, dermatophytes, and Malassezia affect many patients, especially those with immunosuppression from metabolic or systemic disease. Candidal infections form in warm, wet areas, such as skin folds and mucosal surfaces. Cutaneous candidiasis appears as macerated, erythematous plaques with satellite pustules in intertriginous areas. Affected mucosal surfaces, which are often erythematous, may be covered with a friable, removable white film. Treatment entails topical antifungals; drying agents such as aluminum acetate soaks; and, if inflammation is significant, a low-potency topical corticosteroid for a short time.

Infections with dermatophytes, especially Trichophyton rubrum and T mentagrophytes, cause tinea infections, further described in Table 1. Typical lesions consist of annular patches with central clearing and a leading edge of scale on the body (Figure 1). Tinea unguium, or onychomycosis, has several subtypes, such as distal lateral subungual (subungual hyperkeratosis and onycholysis, yellow-white in color), white superficial (small, white, powdery patches with roughened, crumbling nails), proximal subungual (areas of white discoloration in the proximal nail that move distally as the nail grows), and candidal onychomycosis (which often develops in patients with immunosuppression and affects several or all digits). Culture of the nail and subungual debris can aid in making the diagnosis and in confirming the underlying organism.3

Oral terbinafine (250 mg daily) taken for 6 weeks for fingernails and 12 weeks for toenails is considered the current systemic treatment of choice for dermatophyte therapy, with complete cure rates of 38% in 12-week studies, and mycologic cure rates of 70%.8 Relapses are common, and monitoring of liver function tests before, during, and after treatment is necessary. A recently FDA-approved topical medication, efinaconazole solution, 10% (the first FDA-approved topical triazole for toenail onychomycosis), administered daily for 52 weeks, also demonstrated success in phase 3 trials, resulting in complete cure rates of 26% and mycologic cure rates of 55%.22 This solution penetrates the nail with fewer adverse effects and requires no blood monitoring; thus, it is an optimal remedy for patients with comorbidities that prevent them from taking oral antifungals.

Cutaneous viral infections can present in myriad ways. Human papillomavirus infections frequently occur as recurrent skin and anogenital warts, which can be disfiguring and can cause a considerable psychological burden to patients. High-risk subtypes of HPV, including HPV 16 and 18, are major causes of cervical cancers and a subset of vaginal, vulvar, penile, anal, oropharyngeal, and digital neoplasms. Recalcitrant warts should be referred to dermatologists for further evaluation and biopsy to rule out other entities.

Because most primary care clinicians are familiar with reactivation of varicella-zoster virus, or shingles/zoster (Figure 2), and herpes simplex virus (HSV), a thorough discussion is unnecessary in this article. It is important to note, however, that recurring shingles in the groin area, including the buttocks, even if unilateral, is often recurrent HSV rather than recurrent shingles; thus, suppressive therapy for HSV-2 in the groin may be beneficial.4 Table 1 describes in more detail common viral diseases frequently encountered in the primary care setting.

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Select Systemic Diseases

Along with the common primary dermatologic diseases already described, many cutaneous stigmata of systemic disease exist.9 Several skin lesions would prompt a practitioner to initiate a systemic evaluation for underlying disease, as delineated in Table 2.

Common Cutaneous Neoplasms

In the course of the routine physical examination, primary care physicians should take the opportunity to examine the skin for neoplasms. Recognition of common benign lesions that do not warrant further evaluation is important, as well as those lesions that may require closer inspection or biopsy. Common growths encountered include melanocytic nevi, seborrheic keratosis, and dermatofibromas.

Melanoyctic Nevi 

Melanocytic nevi, or “moles,” can be divided into compound nevi (both epidermal and dermal component), intradermal nevi (nests of melanocytes in the dermis only), and junctional nevi (at the junction of the dermis and epidermis). Melanocytic lesions can appear across a spectrum: as pink papules to flat, light, or dark brown macules, even to very dark or blue papules and macules. 

Melanocytic lesions that meet the criteria of the mnemonic ABCDE would prompt a biopsy or referral to a dermatologist10: 

• A for asymmetry of the lesion

• B for border irregularity (notched, moth-eaten, scalloped, etc)

• C for color variation within moles (red and white or lighter areas, not just darker areas)

• D for diameter larger than 6 mm

• E for evolving or changing lesions 

Of note, nonmelanocytic lesions can meet the ABCDE criteria; however, they do not need a biopsy unless they have other concerning features.

Seborrheic Keratosis

Seborrheic keratosis, which represents a proliferation of keratinocytes, is the most common benign tumor of older patients. They possess variable appearances, often as stuck-on, pink to light brown to dark, verrucous papules, which can surface anywhere on the body, though most often on the trunk and upper extremity. Their etiology is unknown. Seborrheic keratosis can be irritating or pruritic and raise concerns of malignancy to the untrained eye.

Dermatofibromas

Dermatofibromas, or benign fibrous histiocytomas, are benign papules or nodules that also have a variable appearance, sometimes as a pink to brown firm papule that invaginates when pressure is applied. At times, they can be itchy or symptomatic, though in most patients they are asymptomatic.

Cutaneous Malignant Neoplasms 

Cutaneous malignant neoplasms are also frequently encountered first by primary care providers, including melanoma (Figure 3), basal cell carcinoma (Figure 4), and squamous cell carcinoma (Figure 5). The incidence of all types of skin cancer are rising: 1 in 5 Americans develop skin cancer during their lifetime.11 Risk factors include
ultraviolet light exposure, chemical exposure, immunosuppression, genetic predisposition, and lighter skin types as graded on the Fitzpatrick skin type scale: Type I is very pale skin that never tans and always burns, and type VI is the darkest skin type that rarely burns.12

Photoprotection, crucial in preventing both skin cancers and photoaging, includes strategies such as avoiding the sun, seeking shade, wearing protective clothing, and administering sunscreen. Table 3 reviews common cutaneous malignancies, their clinical appearance, and their treatment options. 

Patients frequently present with cutaneous concerns to the primary care practitioner. This series reviewed common problems—including eczema, psoriasis, eyelid dermatitis, skin infections, and cutaneous neoplasms—to increase awareness of and treatment options for myriad skin conditions. Practitioners should feel more comfortable addressing their patient’s skin concerns, initiating treatment for common skin diseases, and understanding when referral to a dermatologist may be warranted.

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Topical Corticosteroidsfor Dermatologic Conditions:Clinical Considerations

Topical corticosteroids are frequently prescribed for a variety of inflammatory dermatologic conditions. Vehicle considerations reviewed in Table 4. Table 5 enumerates skin conditions treatable with topical corticosteroids, which are divided into 7 classes by potency based on the ability to constrict blood vessels. For instance, class 1 agents are 600 to 1000 times stronger than over-the-counter (OTC) hydrocortisone, 1%. The concentration is minimally relevant, while fluorination increases the potency and the potential for adverse effects.

Physicians should familiarize themselves with at least one medication in each class—for example: class 1, clobetasol propionate; class 2, fluocinonide/desoximetasone; class 3 betamethasone valerate/fluocinolone acetonide; class 4, triamcinolone acetonide/mometasone furoate; class 5, hydrocortisone valerate; class 6, desonide; class 7, OTC hydrocortisone.

Several principles exist when treating patients with topical corticosteroids:5,6

• Ultra-high potency topical corticosteroids should not be used continuously for longer than 3 weeks, except in select cases.

• Low-to-high potency topical corticosteroids should not be used continuously for longer than 3 months to avoid adverse effects.

• Combination topical corticosteroids and antifungal agents should generally be avoided to reduce the risk of adverse effects and tinea infections of the skin.

• If the condition is acute, higher-potency corticosteroids may be administered for a short time. Skin that is denuded absorbs more corticosteroid than does intact skin. The degree of the skin’s thickness and hyperkeratosis also determine the amount of product absorbed. 

Evaluating treatment options for a dermatitis with these notions in mind will help a practitioner choose the right potency and vehicle for a particular condition.

Once- or twice-daily application is advisable for most diseases. More frequent application does not result in clinical improvement. The amount of product that should be applied to a particular area can be estimated by the fingertip unit (FTU) method, defined as the amount of product that can be dispensed from the fingertip to the first finger crease from a tube with a 5 mm diameter nozzle.7 One FTU equals 0.5 g, which equals approximately 2 handprints or 2% body surface area. Table 6 gives approximate dosing amounts depending on areas treated. 

Possible side effects of corticosteroids include atrophic changes of the skin, such as easy bruising, increased fragility, thinning, and striae, and worsening of cutaneous infections. Rare systemic effects are possible with ultra-potent corticosteroids over large surface areas, including Cushing disease, hypothalamic-pituitary-adrenal axis suppression, decreased growth rate, and aseptic necrosis of the femoral head.5

Mary P. Maiberger, MD, is the chief of dermatology at the VA Medical Center, assistant professor of dermatology at Howard University School of Medicine, and assistant clinical professor of dermatology at George Washington University School of Medicine, all in Washington, DC.

Julia R. Nunley, MD, is a medical dermatologist and professor in the department of dermatology at Virginia Commonwealth University in Richmond, VA.

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