Differentials
Seborrheic dermatitis
SIGNS / SYMPTOMS
Yellow greasy scales on an erythematous base in a seborrheic distribution (periorificial and on the scalp). Usually scaly.
INVESTIGATIONS
Clinical differentiation usually suffices.
Contact dermatitis
SIGNS / SYMPTOMS
Vesicles and pseudovesicles.
INVESTIGATIONS
Patch testing will be positive for specific contact allergens.
Systemic lupus erythematosus
SIGNS / SYMPTOMS
Discoid or malar "butterfly" distribution; rash often associated with photosensitivity; oral ulcers are common. Serositis, renal disorders, neurologic disorders, hematologic disorders, and immunologic disorders may occur.
INVESTIGATIONS
Antinuclear antibody positive; hypocomplementemia; anti-Ro antibodies positive; anti-double-stranded DNA antibodies positive.
Dermatomyositis
SIGNS / SYMPTOMS
Periorbital confluent macular violaceous (heliotrope) erythema, Gottron papules, pruritus and/or burning of the skin, sensitivity to sunlight, muscle weakness, pain, and tenderness.
INVESTIGATIONS
Positive antinuclear antibody (speckled and nucleolar immunofluorescence pattern); anti-Jo-1 antibody positive.
Photodermatitis
SIGNS / SYMPTOMS
General erythema in photodistribution.
INVESTIGATIONS
Clinical differentiation usually suffices.
Carcinoid syndrome
SIGNS / SYMPTOMS
Flushing, diarrhea, bronchoconstriction; right-sided cardiac valve disease.
INVESTIGATIONS
Elevated 24-hour urinary 5-hydroxyindoleacetic acid (5-HIAA) levels.
Mastocytosis
SIGNS / SYMPTOMS
Flushing, pruritus, urtication, abdominal pain, nausea or vomiting, diarrhea, musculoskeletal pain, headache, vascular instability, neuropsychiatric difficulties.
INVESTIGATIONS
Presence of dense infiltrate of mast cells on tissue biopsy.[38]
Polycythemia vera
SIGNS / SYMPTOMS
History of bleeding or thrombosis. Other common clinical features include headache, generalized weakness, splenomegaly, excessive pruritus, plethora, or erythromelalgia (tenderness or painful burning and/or redness of fingers, palms, heels, or toes).
INVESTIGATIONS
Presence of elevated hemoglobin and normal arterial oxygen.
Sarcoidosis
SIGNS / SYMPTOMS
Translucent yellow-red papules that appear as an "apple jelly" when compressed with a glass slide (diascopy).
INVESTIGATIONS
Characteristic granulomatous findings on biopsy of sarcoidal skin lesions, sometimes nonspecific.
Dermatitis due to long-term use of corticosteroids
SIGNS / SYMPTOMS
Generalized redness with atrophy of skin; possible striae.
INVESTIGATIONS
Clinical differentiation usually suffices.
Acne vulgaris
SIGNS / SYMPTOMS
Typically affects younger people and begins with puberty. Presence of whiteheads (closed comedones) and blackheads (open comedones). Lack of flushing and lack of significant erythema.
INVESTIGATIONS
Clinical differentiation usually suffices.
Allergic conjunctivitis
SIGNS / SYMPTOMS
Presence of a watery or ropy mucoid discharge. Itching is the primary symptom. It is most commonly seasonal and often associated with a history of atopic dermatitis, hay fever, and asthma.
INVESTIGATIONS
Clinical differentiation usually suffices.
Inflammatory keratosis pilaris
SIGNS / SYMPTOMS
Most often limited to the extremities, and presents with more distinct papules (as opposed to papules on a background of erythema as seen in rosacea). A more inflammatory form of keratosis pilaris can sometimes be confused with rosacea. While keratosis pilaris is extremely common, making a clinical distinction between rosacea and keratosis pilaris is not often difficult.
INVESTIGATIONS
Clinical differentiation usually suffices.
Demodex folliculitis
SIGNS / SYMPTOMS
Demodex folliculitis on the face and trunk presents with a clinical picture that can be almost identical to rosacea.
INVESTIGATIONS
Skin scraping will demonstrate numerous demodex mites.
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