Differentials
Impetigo
SIGNS / SYMPTOMS
Most frequently occurs in early childhood.
Macules, which develop into vesicles and form golden-yellow crusts.
Most often affects exposed areas on the face, hands, and extremities.
Xerotic dermatitis
SIGNS / SYMPTOMS
Symmetric areas of xerosis with diffuse scale.
Worsens in severity distally (forearms >proximal arms).
Linear burrows not seen.
INVESTIGATIONS
No differentiating tests.
Folliculitis
SIGNS / SYMPTOMS
Multiple follicular-based erythematous papules or pustules on chest and back.
No burrows seen on physical exam.
Allergic contact dermatitis
SIGNS / SYMPTOMS
May have a suspected exposure.
Characteristic distribution depending on location of contact with allergen.
Usually characterized by scaly patches without burrows.
Pruritus tends not to be increased at night.
INVESTIGATIONS
No differentiating tests.
Dermatitis herpetiformis
SIGNS / SYMPTOMS
Chronic relapsing eruptions of grouped symmetrical, pruritic papulovesicles on scalp, neck, extensors, and buttocks.
May have gastrointestinal symptoms consistent with celiac disease.[24]
INVESTIGATIONS
Biopsy of dermatitis herpetiformis will show neutrophils in the dermal papillae on hematoxylin and eosin stain sections and granular foci of IgA in the dermal papillary tips on direct immunofluorescence.[24]
Bullous pemphigoid
SIGNS / SYMPTOMS
Tense bullae on torso and/or extremities.
Scabies prep, biopsy for hematoxylin and eosin (H&E), and immunofluorescence are helpful in distinguishing these conditions.
INVESTIGATIONS
Biopsy of bullous pemphigoid will show a subepidermal bulla with a predominantly eosinophilic infiltrate on H&E stain, and direct immunofluorescence of perilesional skin will show linear IgG and C3 at the dermal-epidermal junction.[25]
Pruritic urticarial papules and plaques of pregnancy
SIGNS / SYMPTOMS
Urticarial and papular lesions seen in pregnant women in the third trimester.
Associated with greater than average weight gain and abdominal distention.
Begins in abdominal striae and spares the umbilicus.[26]
INVESTIGATIONS
No differentiating tests.
Flea bites
SIGNS / SYMPTOMS
Exposure to a pet or other animal with flea infestation is common. Presents as pruritic papulovesicles more commonly confined to the lower extremities. Linear burrows are not seen.
INVESTIGATIONS
No differentiating tests.
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