Poliosis circumscripta, commonly referred to as a "whiteforelock", is a condition characterized by localized patches of white hair due to a reduction or absence ofmelanin in hair follicles. Although traditionally associated with the scalp, poliosis can affect any hairy area on the body, including eyebrows, eyelashes, and beards. Microscopically, poliosis is marked by the lack of melanin ormelanocytes in thehair bulbs, thoughepidermal melanocytes typically remain unaffected unless associated with conditions likevitiligo.[1]
Poliosis can be congenital and often occurs in the context of various genetic syndromes. These disorders are typically linked to other systemic manifestations.
Tuberous Sclerosis Complex (TSC): TSC is a genetic condition that leads to the formation of benign tumors in multiple organs. Dermatological signs such as hypomelanotic macules and facialangiofibromas are common, and poliosis can occasionally be an early indicator of TSC.[2]
Piebaldism: This rare genetic disorder is characterized by a congenital absence of melanocytes in certain areas of the skin and hair, leading to white patches or forelocks. It results from mutations in theKIT gene, which affects the migration ofmelanoblasts during development.[3]
Waardenburg Syndrome: Thisneural crest disorder is associated withsensorineural hearing loss and pigmentary anomalies, including white forelocks and patches of depigmentation on the skin. Poliosis is a common manifestation.[4]
In addition to genetic factors, poliosis can develop due to various inflammatory, autoimmune, orneoplastic conditions, or as a side effect of medication.
Vitiligo: This autoimmune disorder leads to the destruction of melanocytes, resulting in depigmented skin patches. Poliosis is present in half of patients with segmental vitiligo.[5]
Vogt-Koyanagi-Harada Syndrome (VKH): VKH is a systemic autoimmune disorder affecting melanin-containing tissues, leading touveitis,meningitis, and poliosis, which often involves the eyebrows and eyelashes.[6]
Alopecia Areata (AA): Poliosis may emerge in patients with AA as pigmented hair selectively falls out or during hair regrowth.[7]
Sarcoidosis: This systemic inflammatory disease can affect the eyes and skin, leading to poliosis, particularly in patients with uveitis.[8]
Neoplasms and medication-induced poliosis: Poliosis has been associated with melanocytic lesions such as congenital or acquirednevi andmelanoma. Additionally, poliosis is a rare side effect of certain medications, including topicalprostaglandin analogs (used inglaucoma treatment) and systemic drugs likechloroquine andacitretin.[9][10]
It is sometimes called aMallen streak, after a fictional family with hereditary poliosis. The Mallen family featured in a sequence of novels byCatherine Cookson, of whichThe Mallen Streak was the first. She later adapted them into a TV series calledThe Mallens.
The character ofLily Munster in the American sitcomThe Munsters has two prominent Mallen streaks.
During his tenure as the host ofTalk Soup, hostJohn Henson repeatedly referred to his own poliosis as a "skunk spot".
Cruella De Vil has the appearance of this condition with her half-black/half-white hair.
^Willacy H. (2010)."Tuberous Sclerosis".PatientPlus. Patient.info. RetrievedMay 2, 2011.
^Sleiman R, Kurban M, Succaria F, Abbas O (2013). "Poliosis circumscripta: overview and underlying causes".J Am Acad Dermatol.69 (4):625–33.doi:10.1016/j.jaad.2013.05.022.PMID23850259.
