What is poliosis?
Poliosis is a condition wherein a patch of hair is depigmented.
Melanoblasts, melanocytes and follicular melanogenesisTo understand poliosis we must know the process of pigmentation of hair. Melanin pigments, eumelanin and pheomelanin, give color to hair. Pheomelanin contributes orange and yellow colors and eumelanin subtypes contribute to black or brown hair color. The proportion and combination of these pigments give various hues of human hair color. Melanin pigment is synthesized by melanin producing cells known as melanocytes.
The precursor cells of melanocytes are formed from neural crest cells during embryonic development. The development of neural crest cells, their migration for the formation melanoblasts and the transformation of melanoblasts to melanocytes is brought about by cell protein signaling. Protein signalling is controlled by many genes. Any mutation or deletion in the concerned genes and any disturbances in these processes can manifest as congenetic or genetic poliosis disorders.
Follicular melanocytes synthesize the skin pigment. The melanin granules are transferred into cortical and medulla keratinocyte cells. Finally pigmented hair shafts are formed. Any local disturbance to these processes, either physically or chemically can cause loss of hair and/or poliosis. In autoimmune conditions the follicular melanocytes may be targeted by antibodies and neutralized.
Congenital poliosisPoliosis may be congenital and associated with several genetic disorders and conditions such as Waardenburg syndrome, piebaldism, tuberous sclerosis and giant congenital nevus.
Waardenburg syndrome is a group of genetic disorders characterized by hearing loss and hypopigmentation of skin and hair.
Piebaldism is an autosomal dominant congenital disorder characterized by white forelock and patches of depigmented skin. White patches of hair on the head, eyebrows and eyelashes may be found in persons affected by piebaldism. Mutations in the KIT gene or SNAI2 are causes of this genetic disorder.
Tuberous sclerosis is a rare genetic disease causing benign tumors to grow in many parts of the body including the skin. It is caused by the mutations in TSC1 and TSC2 genes. Patients affected by tuberous sclerosis may develop skin manifestations like white depigmented patches of hair on the head and body.
Giant congenital nevus is sometimes associated with poliosis. G.Yosipovitch et al have reported the occurrence of this disorder in associated with a giant congenital nevus. WJ.Lee et al have described white patch of hair in association with a giant congenital melanocytic nevus on the scalp.
Acquired poliosisAcquired poliosis is reported in conjunction with many benign conditions.
Poliosis may be associated with diseases and disorders like sarcoidosis, GAPO syndrome, idiopathic uveitis, Vogt–Koyanagi–Harada syndrome, vitiligo, Marfan's syndrome, alopecia areata and herpes zoster. In Ho Kwon et al reported a case of poliosis circumscripta associated with neurofibroma.
Marfan syndrome is an inherited autosomal dominant multisystem disorder of the connective tissue. In Marfan syndrome normal body growth is affected with characteristic overgrowth of long bones, abnormalities in skeletal bones, skin and internal organs. Skin manifestations are usually limited to striae distensae. KL. Herman et al had reported a Marfan syndrome case with acquired poliosis and white forelock.
Poliosis and autoimmune diseasesIn autoimmune diseases, the body's immune system mistakenly attacks the body cells. In certain disorders melanocytes may be destroyed by the immune system.
Vogt–Koyanagi–Harada syndrome is an autoimmune disease characterized by progressive uveitis with dermatologic, neurologic and auditory involvement. Poliosis of the eyelashes and eyebrows is often accompanied.
|vitiligo and poliosis|
Vitiligo is an autoimmune disease wherein the body's immune system attacks and destroys the melanocytes.
Alopecia areata is considered to be an autoimmune disorder wherein the hair follicles are destroyed causing hairless patches. White hair patches is also associated with alopecia areata.
Sarcoidosis is inflammatory disease with abnormal collection of granulomas. It can affect multiple organs. Manifestations of sarcoidosis in the eye include uveitis and retinal inflammation. K S Lett et al reported a case of eyelash poliosis in association with sarcoidosis of anterior uvea. The researchers postulated that the depigmentation is the result of an autoimmune mechanism.
Association with malignancy and melanomaAlejandra G. de Alba Campomanes et al reported a case of conjunctival melanoma with eyelid poliosis. Dunn CL et al reported a case of melanoma of the scalp with white hair manifestations. Adel H. Alsuhaibani et al reported a case of primary orbital melanoma With white hair manifestations.
Treatment for poliosisFor treating this disorder, the causative factor has to diagnosed. Treating the cause may resolve the condition in some cases. However, if the causative factors are congenital the treatment becomes impossible. Cosmetic camouflage can help in some poliosis cases.
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1.Sleiman R, Kurban M, Succaria F, Abbas O. Poliosis circumscripta: overview and underlying causes. J Am Acad Dermatol. 2013 Oct;69(4):625-33.
Image author: Klaus D. Peter, Gummersbach, Germany | License: Cc-by-3.0-de
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