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
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Viral infections including varicella zoster (shingles) |
Rocky Mountain spotted fever (RMSF) |
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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
• Give consideration to both infectious and noninfectious etiologies.
History
• Perform a complete review of systems to determine if there are any associated symptoms.
• Note the sexual history and immunization history.
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.
| Clinical Entities | Medical Knowledge |
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Varicella Zoster Virus |
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Pφ |
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). |
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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. |
