Porrigo : have you heard this (If not it's normal !)

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If one looks in old dermatology textbooks which includes Alibert’s (1768-1837) famous atlas; on will surely stumble upon this term. By trying to find the skin condition corresponding to this term, one quickly realizes that there is a great confusion surrounding this word.
Willan and Bateman (first half of the 19th century) show in their atlas a picture which clearly shows alopecia areata (under which porrigo is written)
At the same time, Gruby discovers the fungi responsible for hair tinea infections. By publishing this famous discovery he refers to porrigo (here alopecia areata) as being caused by a fungus but all researchers cannot confirm this fact.

Later on, many conditions of the scalp will be referred as “porrigo”. In Alibert’s atlas, there is another term referring to porrigo – pityriasis amiantacea (tinea amiantacea).
It is known today in French as “fausse teigne amiantacée” (false pityriasis amiantacea); and in English as pityriasis amiantacea
In English the term “false pityriasis amiantacea” doesn’t exist and Pityriasis amiantacea (also known as tinea amiantacea) refers to an eczematous condition of the scalp with thick adherent scales which can result in hair loss. According to Bolognia’s textbook, his condition is most often seen in psoriasis, but may also be seen in secondarily infected atopic dermatitis, seborrheic dermatitis, and tinea capitis.
Nowadays, the term pityriasis amiantacea (tinea amiantacea) is therefore a purely descriptive one. If no cause is found, the term idiopathic pityriasis amiantacea should be used.

To conclude with the term porrigo, it has also been used next to an image of impetigo and labelled porrigo larvalis and this terminates the use of this now forgotten term.

Contributors

Dr Christophe Hsu – dermatologist. Geneva, Switzerland

Source of information: Harms M. Dermatologica Helvetica (The Swiss Journal of Dermatology and Venereology: www.dermatologicahelvetica.com