Blaschko's lines, also called the lines of Blaschko, are lines of normal cell development in the skin. These lines are only visible in those with a mosaic[1][2][3] skin condition or in chimeras where different cell lines contain different genes. These lines may express different amounts of melanin,[4] or become visible due to a differing susceptibility to disease. In such individuals, they can become apparent as whorls, patches, streaks or lines in a linear or segmental distribution over the skin. They follow a V shape over the back, S-shaped whirls over the chest and sides, and wavy shapes on the head.[5][6] Not all mosaic skin conditions follow Blaschko's lines.[7]

Blaschko's lines
Incontinentia pigmenti forming along Blaschko's lines in a 3-year-old girl

The lines are believed to trace the migration of embryonic cells.[8][9] They do not correspond to nervous, muscular, or lymphatic systems. The lines are not unique to humans and can be observed in other non-human animals with mosaicism.[10][11]

Alfred Blaschko is credited with the first demonstration of these lines in 1901.[12]

Signs and symptoms


The skin lesions that follow Blaschko's lines are varied. They include genetic, congenital and acquired (i.e., non-genetic) conditions.[13] Examples include:



Alfred Blaschko, a private practice dermatologist from Berlin, first described and drew the patterns of the lines of Blaschko in 1901. He obtained his data by studying over 140 patients with various nevoid and acquired skin diseases and transposed the visible patterns the diseases followed onto dolls and statues, then compiled the patterns onto a composite schematic of the human body. He described a system of lines across the surface of the human body that nevi and dermatological diseases tended to follow, unrelated to the dermatomes of the body or any other cutaneous or subcutaneous structure.[14] In the same month of 1901, an American dermatologist named Douglas Montgomery presented his own research paper before the American Dermatological Society, based on his studies of extensive linear nevi in human patients. Similar to Blaschko, he suggested that the linear patterns of nevi followed "streams" of tissue growth that occurred during embryogenesis rather than being related to an epidermal structure.[15]

In 1945, the Journal of Heredity published Russian scientist Moisey Davidovich Zlotnikov's research describing a 24-year-old woman with a unilateral, systematized nevus across the left side of her body, and proposed that the disorder was due to a mutation during the cell cleavage stage of development. Based on this hypothesis, Zlotnikov suggested that the only probable explanation for the sagittal asymmetry of the disease was a genetic mosaicism in the patient.[2] However, this proposal was not widely explored until re-hypothesized by German dermatologist Rudolf Happle in the 1970s[16] due to the state of genetic and medical research in the Soviet Union at the time, and recent end of World War II.[2]

The lines of Blaschko were first referred to as such by the English-speaking medical community after 1976, when Robert Jackson published a review and reconsideration of Blaschko's research. Jackson wished to inspire interaction between dermatologists who saw Blaschko's lines in patients, and developmental biologists studying embryology and chromosomal abnormalities such as mosaicism.[17]

Scientists such as Rudolf Happle and Jean Bolognia have further differentiated Blaschko's lines from other linear phenomena such as Langer's lines and expanded the map of the lines over the human body to include areas of the head, face, and neck, where Blaschko's original maps did not cover.[14] In 1985, Rudolf Happle proposed a link to lyonization and investigated the link to other X-linked skin disorders. Since that year, Scientists have continually explored the developmental hypothesis for the origins of Blaschko's lines, having found biological evidence to support the theory and linking the lines to other mosaicism and genetic-development related conditions and phenomena of the skin.[18][19]

See also



  1. ^ Fitzpatrick JE, High WA (2017). "17, Linear and Serpiginous Lesions". In Kyle WL (ed.). Urgent Care Dermatology: Symptom-Based Diagnosis. Elsevier. pp. 289–300. ISBN 978-0-323-49709-1.
  2. ^ a b c Happle R, Haneke E (August 2021). "More about Zlotnikov, the Man Who Explained Blaschko's Lines to be a Mosaic". Acta Dermato-Venereologica. 101 (8): adv00521. doi:10.2340/00015555-3880. PMC 9413650. PMID 34263329. S2CID 235907280.
  3. ^ Roach ES (2004). Neurocutaneous Disorders. Cambridge University Press. p. 98. ISBN 978-0-521-78153-4.
  4. ^ Madan, Kamlesh (2020-09-01). "Natural human chimeras: A review". European Journal of Medical Genetics. 63 (9): 103971. doi:10.1016/j.ejmg.2020.103971. ISSN 1769-7212. PMID 32565253.
  5. ^ Brown PM (2002). Transcription. CRC Press. p. 38. ISBN 978-0-415-27200-1.
  6. ^ Tenea D (2016-12-22). "The Puzzle of the Skin Patterns". Integrative Medicine International. 4 (1–2): 1–12. doi:10.1159/000452949. ISSN 2296-7362.
  7. ^ Molho-Pessach, Vered; Schaffer, Julie V. (2011-03-01). "Blaschko lines and other patterns of cutaneous mosaicism". Clinics in Dermatology. Advances in Dermatologic Diagnosis: Part I. 29 (2): 205–225. doi:10.1016/j.clindermatol.2010.09.012. ISSN 0738-081X. PMID 21396561.
  8. ^ Harper J. Textbook of Pediatric Dermatology. p. 691. ISBN 0-86542-939-1.
  9. ^ Ruggieri M (2008). Neurocutaneous Disorders: Phakomatoses & Hamartoneoplastic Syndromes. Springer. p. 569. ISBN 978-3-211-21396-4.
  10. ^ Muller G, Kirk R (2001). Muller & Kirk's Small Animal Dermatology. Elsevier Health Sciences. p. 9. ISBN 978-0-7216-7618-0.
  11. ^ Gross TL (2004). Veterinary Dermatopathology. Wiley-Blackwell. p. 156. ISBN 978-0-632-06452-6.
  12. ^ Blaschko A (1901). Die Nervenverteilung in der Haut in ihre Beziehung zu den Erkrankungen der Haut [The distribution of nerves in the skin in their relation to diseases of the skin] (in German). Vienna, Austria & Leipzig, Germany: Wilhelm Braumüller. From p. 41: "Ganz ohne meinen Willen … das ich Ihnen bieten kann." (Quite without my intending it, these stripe-form naevi [i.e., skin lesions] and dermatoses have become the main object of my work: in part this is perhaps because much material was collected especially about this disorder. I don't want to repeat myself, but I would like to refer you, above all, to Plate XVI on p. 93, [figures] 1 and 2, the diagram of naevus lines, which, if I may say so, represent the quintessence of my work and perhaps is the one essentially new [thing] that I can offer you.) Kim is wrong See also p. 15.
  13. ^ Bolognia JL, Orlow SJ, Glick SA (August 1994). "Lines of Blaschko". Journal of the American Academy of Dermatology. 31 (2 Pt 1): 157–190. doi:10.1016/S0190-9622(94)70143-1. PMID 8040398.
  14. ^ a b Tagra S, Talwar AK, Walia RL (January 2005). "Lines of Blaschko". Indian Journal of Dermatology, Venereology and Leprology. 71 (1): 57–59. doi:10.4103/0378-6323.13796. PMID 16394371.
  15. ^ Montgomery DW (1901). "The cause of the streaks in naevus linearis". Journal of Cutaneous and Genito-Urinary Diseases. 19: 455–464.; Montgomery DW (October 2001). "The cause of the streaks in naevus linearis". Archives of Dermatology. 137 (10): 1291. ISSN 0003-987X.
  16. ^ Molho-Pessach V, Schaffer JV (2011-03-01). "Blaschko lines and other patterns of cutaneous mosaicism". Clinics in Dermatology. Advances in Dermatologic Diagnosis: Part I. 29 (2): 205–225. doi:10.1016/j.clindermatol.2010.09.012. PMID 21396561.
  17. ^ Jackson R (October 1976). "The lines of Blaschko: a review and reconsideration: Observations of the cause of certain unusual linear conditions of the skin". The British Journal of Dermatology. 95 (4): 349–360. doi:10.1111/j.1365-2133.1976.tb00835.x. PMID 788770. S2CID 20554924.
  18. ^ Moss C, Larkins S, Stacey M, Blight A, Farndon PA, Davison EV (September 1993). "Epidermal mosaicism and Blaschko's lines". Journal of Medical Genetics. 30 (9): 752–755. doi:10.1136/jmg.30.9.752. PMC 1016532. PMID 8411070.
  19. ^ Happle R (July 1985). "Lyonization and the lines of Blaschko". Human Genetics. 70 (3): 200–206. doi:10.1007/BF00273442. PMID 3894210. S2CID 6702466.