Infections Presenting with Rash (Case 46)

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Chapter 54
Infections Presenting with Rash (Case 46)

Patricia D. Brown MD

Case: A 68-year-old man presents in late August with a complaint of skin rash. Two days earlier, the patient first noticed several red, raised lesions on the left chest wall; the morning of presentation he awoke with a burning pain in that area and noticed multiple lesions, some of which appeared to be filled with fluid. He denies fever or any other specific complaints. His past medical history is remarkable only for hypertension, for which he has taken lisinopril for the past 3 years. He is retired and has no pets. The patient is a resident of Boston who travels frequently to his vacation home on Cape Cod; his last visit there was 6 weeks ago. Three days ago he returned from a family reunion in a rural area of Arkansas. He golfed and fished, spending large amounts of time outdoors, but recalls no insect bites. He is widowed and has not been sexually active for many years. He has no sick contacts. He received the 23-valent pneumococcal polysaccharide vaccine at age 65 years and receives the influenza vaccine yearly; his last tetanus shot was 8 years ago, and he has received no other vaccinations. On physical exam the patient has normal vital signs but appears in mild discomfort secondary to pain. The only abnormal finding is a rash that extends from the midchest to the midback, appearing to follow the T6 dermatome. The rash consists of papular and vesicular lesions on an erythematous base; some lesions are filled with clear fluid, and others appear pustular.

Differential Diagnosis

Viral infections including varicella zoster (shingles)

Rocky Mountain spotted fever (RMSF)

Lyme borreliosis

Disseminated gonococcal infection (DGI) in patients who are sexually active

 

Speaking Intelligently

The differential diagnosis of a rash is extraordinarily broad, including both infectious and noninfectious etiologies. Numerous viral and bacterial infections can manifest as skin lesions; patients presenting with skin lesions may rarely have a disseminated fungal infection. Noninfectious causes of skin rash include drug reactions and contact or photosensitivity dermatitis. The differential diagnosis must take into account the salient points of the history, as well as the clinical appearance of the skin lesions and any other associated abnormal physical findings.

PATIENT CARE

Clinical Thinking

• When approaching a patient with rash, start with a very thorough investigation of the history in relation to the onset, initial appearance, and evolution of the skin lesions, as well as a very detailed history regarding underlying illnesses, associated symptoms, and potential exposures.

• Give consideration to both infectious and noninfectious etiologies.

• Although the examination will focus on the characteristics, location, and distribution of the skin lesions, a complete physical examination should be performed to determine if any other abnormal physical findings are present that could assist in narrowing the differential diagnosis.

• Because the differential diagnosis is initially quite broad, findings from the history and physical examination should be used to narrow the differential diagnosis so that diagnostic testing (if necessary) can be appropriately directed.

History

• Include the details regarding the skin lesions—that is, when and where they were first noticed, the initial appearance of the lesions, and how the skin lesions have spread or changed since they first appeared to the time of the current presentation.

• Perform a complete review of systems to determine if there are any associated symptoms.

• List the current medications and when they were started, as well as any other medications taken in the preceding 4 weeks.

• Review carefully any occupational exposures, recreational exposures, travel (including activities and exposures in addition to destination), pets, and sick contacts.

• Note the sexual history and immunization history.

• The time of year can greatly influence the differential diagnosis of skin lesions, particularly in patients with associated fever.

Physical Examination

• Carefully examine all skin lesions, noting their distribution. The characteristics of the rash (macular, papular, petechial, vesicular, nodular) will assist in narrowing the differential diagnosis.

• Inspect the conjunctivae, the oral mucosa, and the genital region to look for additional lesions.

Tests for Consideration

In some instances a diagnosis can be made presumptively based on clinical findings; in other cases additional testing (e.g., cultures, serologic testing) will be required to confirm the diagnosis or exclude other diagnoses.

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Varicella Zoster Virus

Varicella zoster virus (VZV) is a medium-sized double-stranded DNA (dsDNA) virus that is a member of the herpesvirus group. Primary varicella infection (chickenpox) is acquired via the respiratory route. During the primary infection, the virus enters sensory nerve endings and establishes latent infection in dorsal root ganglia; infection is lifelong. Reactivation of viral infection may occur, and the virus travels centripetally from the dorsal root ganglion to the skin via the peripheral nerves to multiply in the skin, causing the formation of an eruption in a dermatomal distribution. Sensory symptoms (burning, paresthesias) may precede the development of the skin lesions by several days. Occasionally the host immune response will contain the viral reactivation before the skin lesions form, giving a syndrome of acute neuritis without the skin lesions (zoster sine herpete).

TP

Patients with zoster typically present with a skin rash in a dermatomal distribution; several contiguous dermatomes may be involved. When the first branch of the fifth cranial nerve is involved, zoster ophthalmicus must be considered. This is a sight-threatening condition requiring prompt ophthalmologic evaluation. The skin rash consists of vesicular lesions on an erythematous base that appear in groups (crops); lesions are generally in various stages of evolution (vesicles, pustules, and crusted lesions). Pain from the acute neuritis can be quite severe. Patients may develop persistent pain (postherpetic neuralgia [PHN]) that can be very debilitating. Age > 60 years is a risk factor for PHN.

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