Comment
Etiology and Presentation
En coup de sabre is a rare subtype of linear morphea that involves the frontoparietal scalp and forehead.7,12,13 It manifests as a solitary, linear, fibrous plaque that involves the skin, underlying muscle, and bone.7 Although most cases present with a single lesion, multiple lesions can occur.8 The exact etiology of this disease remains to be determined but is characterized by thickening and hardening of the skin secondary to increased collagen production.7 The incidence of linear morphea ranges from 0.4 to 2.7 cases per 100,000 individuals and is more prevalent in white patients and women.14 Linear morphea is commonly found in children. Children are more likely to have linear morphea on the face, which can lead to lifelong disfigurement.2 Although the disease peaks in the fourth decade of life for adults, most pediatric cases are diagnosed between 2 and 14 years of age.14-16
Pathogenesis
Clinical and histopathological data suggest that a complex interaction among the vasculature, extracellular matrix, and immune system plays a role in the pathogenesis of the disease. Similar to scleroderma, the CD4 helper T cell may be involved in the fibrotic changes that occur within these lesions.17 Early in the disease process, TH1 and TH17 inflammatory pathways predominate. The late fibrotic changes seen in scleroderma are more associated with a shift to the TH2 inflammatory pathway.17 Infection with Borrelia burgdorferi has been implicated abroad, but a large-scale study confirming Borrelia as a pathologic factor within morphea lesions has not been completed to date.18-20 Some authors believe early lesions of ECDS mimic erythema chronica migrans, with the late lesions resembling acrodermatitis chronica atrophicans.20
Histopathology
Histopathologic findings of morphea tend to vary depending on the stage of the disease. The 2 stages of morphea can be differentiated by the degree of inflammation present histologically.14,21 The early phase of morphea primarily affects the connective and subcutaneous tissue surrounding eccrine sweat glands.14,21 A dense dermal and subcutaneous perivascular lymphocytic infiltrate with a mixture of lymphocytes, plasma cells, and histiocytes is commonly observed.5 Later stages of the disease demonstrate densely packed homogenous collagen with minimal inflammation and loss of eccrine glands and blood vessels.14,21 The adipose tissue is generally replaced by sclerotic collagen, giving the biopsy a squared-off appearance.5,14
Management
En coup de sabre presents a treatment challenge. In active lesions, topical or intralesional corticosteroids are considered treatment of choice.5 Methotrexate has proven useful in the treatment of acute and deep forms of linear morphea. A study examining methotrexate in juvenile localized scleroderma, with the majority of patients having the linear subtype, revealed that methotrexate is both efficacious and well tolerated.22 Other reports in the literature reveal efficacy with the use of intravenous corticosteroids and methotrexate combination therapy for treatment of morphea.23,24 A longitudinal prospective study examining the use of high-dose methotrexate and oral corticosteroids for the treatment of localized scleroderma yielded positive results, with patients showing clinical improvement within 2 months of initiation of combination therapy.25 Other treatments include excimer laser; calcipotriene and tacrolimus; and surgical approaches such as autologous fat grafting, grafting with muscle flaps, and tissue inserts.21,26-31 In addition, patients can choose to forego therapy, as was the case with our patient.
Conclusion
En coup de sabre is a rare subtype of linear scleroderma that is limited to the ipsilateral scalp and face predominately in children and women. Neurologic involvement is common and should prompt a comprehensive neurologic workup in patients suspected to have ECDS or PHA. Current treatment recommendations include topical, intralesional, and oral corticosteroids; methotrexate; and surgical grafts. Although ECDS is a rare entity, more intensive research is needed on the exact pathophysiology and effective treatment options that focus on improving the cosmetic outcome in these patients. Cosmesis is the primary concern in patients with ECDS and should be managed early and appropriately to prevent long-term psychological sequelae.