Piebaldism: rare but all dermatologists have heard this strange term during residency
- It comes from Latin:
- Tinea = insect (mite)
- The term tinea was used by our predecessors to name diseases of the scalp.
- One can imagine that certain conditions of the scalp had an appearance like being “eaten by mites”; that is probably what inspired them to use this term.
- Since Dr Alphonse Devergie (1798-1879), this term is limited to affections caused by a fungus.
- Tinea Amiantacea named by Dr Alibert (1814) was later renamed “false Tinea Amiantacea” ((f)TA; fausse teigne amiantacée in French) by Dr Raymond Sabouraud (1864-1938). It is not actually due to a fungus (nor a dermatophyte)
- Dr Sabouraud based himself on the works of Dr David Gruby (1810-1898) and was able to determine different species of dermatophytes with the aid of a culture medium which bear his name (Sabouraud agar medium). In (f)TA, he was unable to demonstrate the presence of a dermatophyte.
- (F)TA is nowadays considered a form of extreme seborrheic dermatitis of the scalp. It can be localized to certain parts of the scalp or diffuse.
- It is often seen in children.
- It is characterized by thick, greyish and shiny scales which look like asbestos (“amiante” in French).
- The hair shafts go through the scales.
- One can lift the scales and make them slide on hair shafts without breaking them.
- Although impressive in appearance, (f)TA is easy to treat with a salicylic-based formulation is enough to make the scales fall off without damaging the hair. If however the hair falls, it will grow back.
- 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, this condition is most often seen in psoriasis, but may also be seen in secondarily infected atopic dermatitis, seborrheic dermatitis, and tinea capitis. Nowadays, this defines the term pityriasis amiantacea (tinea amiantacea) as a purely descriptive one. If no cause is found, the term idiopathic Tinea Amiantacea should be used.
Contributors
Dr Christophe Hsu – dermatologist. Geneva, Switzerland
Source of information: Harms M. Dermatologica Helvetica (The Swiss Journal of Dermatology and Venereology)
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