Table 2. Proposed new classification of pityriasis rosea.*.

Axis 1 – Prodromal symptoms and herald patch Prodromal symptoms – Present (Coryza, fever, generalized muscle pain, fatigue, malaise, arthralgias, gastrointestinal symptoms), Transient/barely noticeable, Absent or unreliable history from patient. Herald patch – Absent, obscure, single, multiple, gigantic, lonely (herald plaque only as manifestation; the disease does not progress beyond the herald plaque).

Axis 2 – Number and distribution of lesions Number – Few lesions (less than five, oligo-lesional), many lesions, sub-erythrodermic, erythroderma due to PR. Distribution – Relatively unilateral, absolutely unilateral, localized, regional, mucosal (mainly oral and genital), acral, PR inversus (PR mainly involving many flexures), shoulders and hips (limb-girdle PR), fewer but larger lesions localized to axillae and groins (pityriasis circinata et marginata of Vidal)**, actinic (photo-distributed), photo-spared.

Axis 3 – Size, morphology, and orientation of lesions Size – Gigantic (PR gigantea of Darier) vs miniature. Morphology – Papular, papulo-squamous, papulo-vesicular, vesicular, lichenoid, urticarial, EM-like, punctuate/ purpuric/ hemorrhagic, follicular.*** Orientation – Typical i.e. along the lines of skin creases (Lines of Langer), – Atypical i.e. not along lines of skin creases: Scattered, Blaschkoid (along lines of Blaschko), Segmental (along a dermatome).

Axis 4 – Symptoms and clinical course Symptoms – Severely pruritic (PR irritata), slightly pruritic, moderately pruritic                   Non-pruritic/asymptomatic Clinical course – Too short (less than two weeks), too long (more than six months) Recurrent PR

Axis 5: Seasonal morphological variations psoriasiform in summer, crusted/haemalis form in winter

* ICD-10, pityriasis rosea is coded L42X00. Pityriasis rosea due to drug is coded L44X01, signifying that PR-like rash related to drugs is now considered a distinct condition. This classification scheme therefore excludes PR or PR-like rashes likely to be related to drugs. ** In ICD-9-CM, pityriasis circinata et maculata was listed as a synonym of PR. In ICD-10, pityriasis circinata, pityriasis circinata et marginata of Vidal, and Gibert’s disease are all listed as synonyms of PR. Some of the variants described in the literature as PR inversus might actually be PR of Vidal. *** Follicular PR is the topic of discussion in the current manuscript.