A herald patch of<unk>  which started before the rest of the lesion and was initially mistaken for a fungal infection Experienced<unk> actitioners may make the diagnosis clinically. Classical symptoms are usually straightforward to recognize, but the wide range of atypical forms may cause difficulty for the clinician in diagnosing some cases. Misdiagnosis by nondermatologists is not uncommon. If the diagnosis is in doubt, tests may be performed to rule out similar conditions such as Lyme disease, ringworm, guttate psoriasis, nummular or discoid eczema, drug eruptions, other viral exanthems. The clinical appearance of<unk>  in some cases is similar to that of secondary syphilis, and rapid plasma reagin testing should be performed if there is any clinical concern for syphilis. A biopsy of the lesions will show extravasated erythrocytes within dermal papillae and dyskeratotic cells within the dermis. A set of validated diagnostic criteria for<unk>  is as follows: A patient is diagnosed as having<unk>  if: # On at least one occasion or clinical encounter, he / she has all the essential clinical features and at least one of the optional clinical features, and # On all occasions or clinical encounters related to the rash, he / she does not have any of the exclusional clinical features. The essential clinical features are the following: # Discrete circular or oval lesions, # Scaling on most lesions, and # Peripheral collarette scaling with central clearance on at least two lesions. The optional clinical features are the following: # Truncal and<unk> oximal limb distribution, with less than 10% of lesions distal to mid-upper-arm and mid-thigh, # Orientation of most lesions along skin cleavage lines, and # A herald patch (not necessarily the largest) appearing at least two days before eruption of other lesions, from history of the patient or from clinical observation. The exclusional clinical features are the following: # Multiple small vesicles at the centre of two or more lesions, # Two or more lesions on palmar or plantar skin surfaces, and # Clinical or serological evidence of secondary syphilis.
Pityriasis rosea
Exanthem
Pityriasis alba
Tinea versicolor
Alopecia mucinosa
Nummular dermatitis
Pityriasis amiantacea
Tinea corporis