Smallpox

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Variola (Smallpox) Mimics: Varicella (Chickenpox) Herpes Zoster (Shingles) Molluscum Contagiosum View Table

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Variola (Smallpox) Back

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Variola (Smallpox) View Table Chart from the Center for Disease Control and Prevention showing the characteristic distribution of smallpox lesions.

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Variola (Smallpox) View Table Smallpox in a child: Notice the characteristic distribution of the lesions, more concentrated on the distal extremities and face and less concentrated on the trunk.

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Variola (Smallpox) View Table Smallpox on the hand: Notice how these lesions have become confluent.

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Variola (Smallpox) View Table Smallpox in a child: Notice the progression and distribution of the lesions from day 1 to day 7.

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Variola (Smallpox) View Table Smallpox in a man: Notice the diffuse and extensive distribution of lesions, with a greater concentration of lesions on his face than on his trunk.

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Variola (Smallpox) View Table Smallpox in a child: Notice that all lesions are in the same stage of development.

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Variola (Smallpox) View Table Smallpox is an acute exanthematous disease caused by infection with the poxvirus variola. The significant clinical features include: Three-day prodromal illness characterized by fever, headache, backache, and vomiting. Generalized centrifugal rash that follows prodrome Begins centrally then spreads to the extremities and face Rapid succession of papules, vesicles, pustules, umbilication, and crusting over a 14-day period. Prior vaccination may alter the clinical presentation of smallpox. The following description applies to the classic presentation in unvaccinated individuals.

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Variola (Smallpox) View Table A macular red rash may precede the appearance of the papules, which are deep and firm to palpation. Papules soon vesiculate, forming a circumscribed, elevated lesion that contains clear fluid. The rash at this point can be very sparse, although individual vesicles can coalesce to form large patches. As the vesicles mature, they turn into pustules. Central umbilication of the pustule is characteristic of smallpox. Eventually, the pustule crusts over and heals with scar formation. A second important distinguishing characteristic of smallpox is that all of the lesions at a given time are in the same stage of development. That is, at any one point in time the lesions are all papules or vesicles or pustules. Bacterial infection of the lesions can occur, producing localized abscesses and cellulitis.

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Varicella (Chickenpox) View Table Chickenpox vesicle behind the ear. Notice the translucent quality of the vesicle on the skin, the classic "dew drop on a rose petal" appearance. Chickenpox on the palate. Notice the glistening, water-drop characteristic of the chickenpox vesicle on the palate.

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Varicella (Chickenpox) View Table Chickenpox on the hand. Notice the simultaneous occurrence of lesions in different stages of development. Chickenpox in an infant. Notice the rose-colored macules, papules, vesicles, pustules, necrotic pustules, and crusted lesions occurring simultaneously.

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Varicella (Chickenpox) View Table Varicella (chickenpox) and herpes zoster (shingles) are distinct clinical entities cause by the varicella-zoster virus (VZV). In young children, prodromal symptoms of chickenpox are uncommon, but in older children and adults, the manifestation of the rash may be preceded by two or three days of fever and chills, malaise, headache, backache, sore throat, and dry cough. The rash begins on the face and scalp and spreads rapidly to the trunk, with relative sparing of the extremities. New lesions arise in crops, usually appearing centrally. Each crop proceeds through a developmental phase, so that at any given time, a patient can have macules, papules, vesicles, pustules, and crusts. In smallpox, by contrast, at any given time, all lesions on the patient's body are in the same phase of development.

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Varicella (Chickenpox) View Table The first sign of chickenpox is rose-colored macules that rapidly progress to papules then to vesicles, then to pustules, and finally to scabbing over with crusts. The typical wall of the vesicle is so thin that it often resembles a drop of water on the reddened surface of the skin (the "dew drop on a rose petal" appearance). As the lesion dries and changes from a vesicle to a pustule, it umbilicates and then crusts over. The crusts fall off in one to two weeks. Scarring is rare unless the lesions become secondarily infected. Vesicles can occur on the mucous membranes, most commonly on the palate; they can also occur in the nose, pharynx, larynx, trachea, gastrointestinal tract, conjunctiva, and vagina.

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Differential Dx - Chickenpox View Table Variola (Smallpox) Begins centrally, then spreads outward to face and extremities All lesions are always in a single stage of development Associated with severe constitutional symptoms Chickenpox Begins on the face and scalp, spreads to the trunk Lesions in various stages of development can simultaneously be present on the patient's skin

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Herpes Zoster (Shingles) View Table Herpes (varicella) zoster on the arm. Notice the characteristic grouping of vesicles Varicella zoster on the face. Notice the dermatomal distribution of the papules, vesicles, and pustules.

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View Table Herpes zoster is a localized disease caused by the varicella-zoster virus (VZV). It is characterized by unilateral radicular pain and a vesicular eruption that is typically limited to one or two dermatomes innervated by a spinal or cranial nerve. The most distinctive characteristics of herpes zoster are its localization and it distribution, which is almost always unilateral. The individual lesions of varicella (chickenpox) and of zoster are identical, but the lesions of zoster evolve more slowly and are characterized by grouped vesicles. The lesions of varicella, by contrast, are more widely distributed. As in varicella, zoster vesicles evolve into pustules, then dry and crust. Herpes Zoster (Shingles)

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Differential Dx – Herpes Zoster View Table Variola (Smallpox) Lesions are widely distributed Lesions at any given time are all at the same stage of development Associated with severe constitutional symptoms Herpes Zoster (Shingles) Lesions are unilaterally distributed along a dermatome Lesions at any given time are in different stages of development (vesicles, pustules, and crusts are in evidence at one time)

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Molluscum Contagiosum View Table Molluscum contagiosum is a common, benign viral infection of the skin and mucous membranes caused by the molluscum contagiosum virus. It typically affects children, but can be transmitted sexually in adults. The mature lesion is an umbilicated papule.

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View Table Lesions begin as small (3 to 6 mm) papules that are smooth, flesh-colored domes with a central dimple. Inside the papule is a white, curd-like core that can be easily expressed. Lesions can occur anywhere on the skin and mucous membranes, but are usually grouped in one or two areas. Occasionally, they may be widely disseminated. Typically fewer than 20 lesions are present, but some individuals may have hundreds. The head, eyelids, trunk, and genitalia are most commonly affected, the genitalia being the predominant site in adults. The lesions are characteristically asymptomatic, but a few patients may complain of itching or may develop an eczematous reaction around the lesions. Molluscum Contagiosum

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Differential Dx – Molluscum Contagiosum View Table Variola (Smallpox) Lesions are widespread Associated with severe clinical symptoms Lesions progress from macules to vesicles to papules to crusts (progression occurs all at the same time in smallpox but at different times in chickenpox) Molluscum Contagiosum Lesions usually grouped in one or two areas Not associated with clinical symptoms Lesions are umbilicated papules only

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