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There’s a Little Zebra in All of Us

December 2, 2017

Nature has an interesting way of identifying animals in the wild. Lions have their manes, leopards have spots. Tigers and zebras have stripes. And apparently, so do people.

Blaschko Lines are common skin patterns that were first identified in 1901 by a German dermatologist named Alfred Blaschko. Over the course of years of examining thousands of patients, he often observed people who exhibited unusual patterns of stripes and swirls that encompassed their entire bodies. Some patterns were restricted to an arm or a leg. Other patients had stripes that ran from head to toe, beginning on their face, migrating to their chest and wrapping around their backs. He called them Blaschko Lines.

After a while, Blaschko noticed that virtually all of his patients that exhibited Blaschko Lines did so in very predictable manners. Looking like a pair of glasses that were painted on with ink, the lines began on the face, circling eyes and lips, then wrapping around the neck and the back of the head. They ran down both arms, legs and curved around his patients’ sides, much like tiger stripes. Interesting though, the lines never crossed the mid-section of his patients’ bodies. Instead, they met in artistic swirls, meandering in an “S” wave over the abdomen, an inverted “U” shape running from the breast to the upper arm, dipping down into a large “V,” before ending in the small of the back. After examining hundreds of patients with Blaschko Lines, he drew an initial, crude diagram of the patterns:

 

Blaschko noticed that the Lines didn’t follow predictable margins of nerves, arteries, veins, lymphatic vessels or muscles. He also noticed that many different types of skin disorders, rashes and moles followed the same patterns he observed on the body, whether the disorder was inherited or acquired. The patterns were also consistent across all races, ages and gender, resulting in the following patterns:

But, what are Blaschko Lines and how are they formed?

Blaschko Lines are cellular relics as the body reproduces from a single cell to a complete organism. Shortly after conception, the fetus begins growing through a predictable process of single cell divisions in all human systems. Some cells duplicate to become organs or muscles. In the skin, the cells continue to grow and migrate along specific lines or margins, depending on their location in the fetus. The cells begin growing from the fetus’s back, moving upward toward the head, sweeping around to the front. Under normal circumstances, each cell contains similar amounts of pigment, so the intersections between the cells aren’t noticeable. Occasionally, the pigment content of the skin cells differs slightly. Imagine sandwiching one light layer of clay between two darker layers, then giving it a twist. The result would be a curved, artistic pattern of clay, much like a Blaschko Line.

Under normal conditions, Blaschko Lines follow predictable patterns, depending on their location: the scalp produces spiral patterns, the face grows swirls around the eyes moving laterally from the angles of the mouth, and vertical lines along the midline. Lines on the trunk follow V-shaped patterns in the middle of the back. Arms and legs produce linear or spiral patterns along their long axis.

While we all have them, Blaschko Lines are usually invisible to the naked eye. They become noticeable in people suffering from congenital, acquired and genetic skin conditions. They include:

Congenital Skin Disorders

  • Linear Darier’s disease
  • Nevus corniculatus
  • Relapsing linear acantholytic dermatosis
  • Hypomelanosis of Ito
  • Syringocystadenoma papilliferum
  • Bart syndrome
  • Epidermal Nevus
  • Inflammatory linear verrucous epidermal nevus
  • Linear and whorled nevoid hypermelanosis
  • Linear basal cell nevus
  • Unilateral nevoid basal cell carcinoma syndrome
  • Nevus depigmentosus
  • Linear eccrine nevi
  • Linear epidermolytic hyperkeratosis
  • Linear nevus comedonicus
  • Linear porokeratosis of Mibelli
  • Nevus sebaceous of Jadassohn

Acquired Skin Disorders

  • Generalized lichenoid drug eruption
  • Lichen striatus
  • Linear atrophoderma of Moulin
  • Linear psoriasis
  • Linear fixed drug eruption
  • Linear lichen planus
  • Extragenital lichen sclerosus
  • Segmental vitiligo
  • Linear mucinoses and mycosis fungoides
  • Linear scleroderma
  • Lichen striatus
  • Lupus erythematosus

Genetic Skin Disorders

  • CHILD syndrome
  • Menke’s syndrome
  • Incontinentia pigmentii
  • Segmental ash leaf spot
  • Focal dermal hypoplasia
  • Conradi-Hunermann syndrome
  • Familial cutaneous amyloidosis, Partington type
  • Melanotic macules of McCune-Albright syndrome
  • Oro-facial-digital syndrome, type I
  • X-linked hypohidrotic ectodermal dysplasia

You can also see Blaschko Lines using black or ultraviolet lights.

According to Dr. Bav Shergill, a physician with the British Association of Dermatologists, surgeons often cut skin along Blaschko Lines during surgery, then sew it up, mimicking the same pattern. “If you follow the line,” says Dr. Shergill, “you often get a better cosmetic outcome, to give the best result.”

Treating Blaschko Lines

Blaschko Lines are typically harmless, non-life threatening disorders. In most cases, they will run their course over several weeks, then disappear as quickly as they appeared. In rare circumstances, they are associated with hypo or hyper pigmentation. Other times, they are associated with skin dryness and itchiness. Topical steroids and emollients are the most commonly prescribed treatments.

Courtesy: Encontext Media

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