A Case of Adult-Onset Lichen Striatus

AFFILIATIONS:
¹Department of Internal Medicine, College of Medicine, University of Arizona, Phoenix, AZ

A 25-year-old woman with no past medical history presented to the dermatology clinic with abrupt onset of an asymptomatic, reddish, inverted-U-shaped papulosquamous skin eruption that started 3 weeks earlier.

History. There were no clear exposures or precipitating events. Over the course of the 3 weeks, the skin lesion acquired a purple color but remained unchanged in size and distribution. Her family history was significant for atopic dermatitis, and the patient denied the use of any medications before the eruption appearing. She also had no history of recurrent sunburns and was not sexually active at that time.

On clinical examination, she had slightly raised and rough, coalescent, violaceous erythematous papules in an inverted U-shaped disposition on the right lumbar regions, extending to the right flank and umbilical region (Figures 1 & 2).

Figures 1 and 2. Coalescent, violaceous erythematous papules in an inverted U-shaped disposition on the right lumbar regions consistent with a lichen striatus eruption, shown at the time of presentation in various lighting.

Diagnostic testing. Her baseline laboratory values, including a complete blood count, comprehensive metabolic panel, and lipid panel, were all within normal limits. Additional testing for autoimmune serologies, including tests for antibody nuclear antigen (ANA), rheumatoid factor, erythrocyte sedimentation rate, and C-reactive protein, were negative or within normal limits. A punch biopsy was done to further elucidate the etiology of the lesion. Histopathology showed hyperkeratosis, necrotic keratinocytes throughout the epidermis, mild spongiosis with exocytosis of lymphocytes, and focal lymphocytic infiltrate at the dermal-epidermal junction. Based on the clinical presentation and characteristics on histology, the eruption was diagnosed as lichen striatus.

Differential diagnosis. In adults, the differential diagnosis includes Blaschkolinear acquired inflammatory skin eruption (BLAISE). BLAISE is a group of inflammatory skin conditions that follow the lines of Blaschko, which include adult blaschkitis, lichen striatus, linear lichen planus, lichen planus-like keratosis, and lupus erythematosus.^1,2

Adult blaschkitis, an inflammatory dermatitis that resembles lichen striatus and is strongly believed to be part of the same spectrum of disease, shares many similarities with lichen striatus.² Both are spongiotic dermatoses that present as asymptomatic, unilateral, linear rashes that are commonly precipitated by stressors. However, lichen striatus is distinct from adult blaschkitis in that it typically affects younger children, causes postinflammatory pigment changes, and takes much longer for the initial rash to resolve.³ These clinical characteristics can help differentiate between these very similar skin conditions.

The appropriate work-up should be done to assess for BLAISE conditions before electing to defer treatment, including baseline laboratories and autoimmune serologies, such as an ANA to assess for lupus erythematosus, for example. Key features of lichen striatus that help differentiate it from other linear dermatoses are the lack of associated symptoms and unique histopathologic findings, specifically the presence of apoptotic keratinocytes throughout the epidermis in conjunction with extension of the lymphocytic infiltrate to the dermal-epidermal junction.^1,2 If lichen striatus is suspected, referral to a dermatologist to acquire a punch biopsy may be diagnostic.

Treatment and management. The condition is self-limiting, so no therapeutic treatments were recommended. The patient denied bothersome symptoms and deferred treatment for symptom control.

Outcome and follow-up. Two months after the emergence of the rash, spontaneous regression of the lesions was observed, along with mild hyperpigmentation. She is doing well to date.

Discussion. Lichen striatus is an uncommon acquired skin disorder that presents as a unilateral, isolated linear rash that is primarily seen in children.^1,4 Lichen striatus initially appears in the skin as numerous pinkish-red, flat-topped papules that coalesce into a linear pattern following the lines of Blaschko.⁴ Lichen striatus is asymptomatic and self-limiting, and children typically do not require treatment.¹

Lichen striatus is rare in adults, with only a handful of cases being identified in the literature. Many cases of lichen striatus in adults in the literature arise following a precipitating event, such as a new medication regimen, vaccination, or trauma.^5-7 Some studies suggest an association with atopic disease, finding that 60% to 85% of children with lichen striatus have a personal or family history of asthma, atopic dermatitis, or allergic rhinitis.^1,8 However, this association has not been investigated in adults. Despite being uncommon, lichen striatus should remain in the differential diagnosis of adults with asymptomatic, unilateral, linear dermatoses, even in the absence of an inciting event.

Lichen striatus is self-limiting, and treatment is typically not required. Occasionally, patients may experience irritation, pruritus, or both, in which case systemic or topical corticosteroids may be used.^1,4 Corticosteroids can help relieve symptoms, but they do not reduce the duration of the rash or the degree of postinflammatory hypopigmentation.⁸ Calcineurin inhibitors, such as tacrolimus and pimecrolimus, are effective in reducing associated pruritus as well.¹ Resolution of symptoms can take anywhere from several months to years.^8,9 Cases of lichen striatus can also be complicated by postinflammatory hypo- or hyperpigmentation once the initial skin rash has resolved, especially in patients with darker complexions.¹⁰ For patients with residual hypopigmentation following lichen striatus, excimer laser treatment can be proposed as a potential treatment to help induce repigmentation.¹¹ In most instances, the postinflammatory hypo- or hyperpigmentation is transient, although it may take several years to fully resolve.¹

Although it is rarely seen in the adult population, lichen striatus should be considered in the differential diagnosis when isolated linear rashes are encountered on physical examination. The lack of symptoms and unique histopathologic findings are key indicators of lichen striatus. The eruption has been demonstrated to occur following a precipitating event and may be associated with atopic conditions. Lichen striatus is inherently benign and self-limiting, and treatment is not recommended for these eruptions.