Lichen striatus is a rare, benign, self-limited linear dermatosis of unknown origin that predominantly affects children. Lichen striatus is clinically diagnosed on the basis of its appearance and characteristic developmental pattern following the lines of Blaschko. 
The etiology of lichen striatus is unknown. Many etiologic or predisposing factors are suggested for lichen striatus. The most commonly accepted hypothesis is the combination of genetic predisposition with environmental stimuli.
Atopy may be a predisposing factor. One group reported that 85% of patients with lichen striatus have a family history of atopic dermatitis, asthma, or allergic rhinitis. However, another report disputes this claim, stating that the incidence of atopy is no greater than that of the general population.
An autoimmune response may also be involved in lichen striatus. A case of lichen striatus has been reported during pregnancy, and it has been postulated that the pregnancy may have triggered an autoimmune response leading to the appearance of the eruption.  Lichen striatus has also been reported concurrently with vitiligo [5, 6] and after adalimumab  and etanercept.  Some reports simply suggest that lichen striatus is an inflammatory skin disease mediated by T cells. It has been reported 17 months after allogenic peripheral blood stem cell transplantation. 
An environmental (infectious or trauma  ) etiology has also been suggested. Familial cases, [11, 12] outbreaks among unrelated children in a shared living environment, and a possible seasonal variation suggest an environmental agent, such as a virus. Support of infectious involvement includes elevations of interleukin 1-beta in lichen striatus biopsy specimens.  However, results of viral testing have not conclusively proven this association. In addition, familial episodes of lichen striatus are not always simultaneous, signifying a possible genetic predisposition as a second explanation. Lichen striatus has been reported to occur shortly following immunization with BCG and hepatitis B vaccination, after UV exposure from a tanning bed,  following a prick from a pineapple leaf, after a bite by a bumblebee,  and after varicella and influenza infection. [16, 17]
One group of authors has suggested that epigenetic mosaicism may be involved. They hypothesize that lichen striatus is triggered by an immunologic reaction to an infection, which triggers methylation or demethylation of a partially silenced genomic element in predisposed patients.  A report of concurrent pityriasis rosea and lichen striatus may lend support to this theory. Human herpes viruses 6 and 7 have been implicated in the etiology of pityriasis rosea. The concurrent lichen striatus eruption may have manifested after being triggered by this viral infection. 
Lesions of lichen striatus follow the lines of Blaschko. [19, 13, 20, 21, 22] Blaschko lines are thought to be embryologic in origin. They are believed to be the result of the segmental growth of clones of cutaneous cells or the mutation-induced mosaicism of cutaneous cells. In lichen striatus, an acquired event (eg, viral infection) may allow an aberrant clone of cutaneous cells to express a new antigen, resulting in the phenotypic skin changes.
No racial predilection is recognized for lichen striatus.
No consensus exists on sex predilection in lichen striatus. Some studies show a 2- to 3-fold increased incidence in girls compared with boys, whereas others show an equal sex distribution.
Lichen striatus is primarily a disease of young children. More than 50% of all lichen striatus cases occur in children aged 5-15 years. Other reports dispute this age range and claim that the median age of onset for lichen striatus is 3 years. Although lichen striatus is rare in both infants and adults, the disease can occur in persons of any age. [23, 24]
The prognosis of patients with lichen striatus is excellent. Recovery is complete. Lichen striatus lesions usually regress spontaneously within 1 year, with a range of 4 weeks to 3 years. Relapses of lichen striatus may occur, but these are uncommon.
Lichen striatus of the nail may take a protracted course, lasting from 6 months to 5 years.  Nail involvement resolves spontaneously without deformity.
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June Kim, MD Mohs Surgeon/Dermatologist, Cascade Eye and Skin Center, PC
Disclosure: Nothing to disclose.
Wingfield Rehmus, MD, MPH Dermatologist, BC Children’s Hospital, Vancouver, British Columbia
Disclosure: Serve(d) as a speaker or a member of a speakers bureau for: Abbvie; Valeant Canada<br/> Received honoraria from Valeant Canada for advisory board; Received honoraria from Pierre Fabre for advisory board; Received honoraria from Mustella for advisory board; Received honoraria from Abbvie for advisory board.
Richard P Vinson, MD Assistant Clinical Professor, Department of Dermatology, Texas Tech University Health Sciences Center, Paul L Foster School of Medicine; Consulting Staff, Mountain View Dermatology, PA
Disclosure: Nothing to disclose.
Paul Krusinski, MD Director of Dermatology, Fletcher Allen Health Care; Professor, Department of Internal Medicine, University of Vermont College of Medicine
Disclosure: Nothing to disclose.
Dirk M Elston, MD Professor and Chairman, Department of Dermatology and Dermatologic Surgery, Medical University of South Carolina College of Medicine
Dirk M Elston, MD is a member of the following medical societies: American Academy of Dermatology
Disclosure: Nothing to disclose.
Daniel J Hogan, MD Clinical Professor of Internal Medicine (Dermatology), Nova Southeastern University College of Osteopathic Medicine; Investigator, Hill Top Research, Florida Research Center
Disclosure: Nothing to disclose.
The authors and editors of Medscape Reference gratefully acknowledge the contributions of previous authors, Nelly Rubeiz, MD, and Amal Mehanna, MD, to the development and writing of this article.
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