Striae distensae (striae, striae atrophicans, stretch marks) are visible scars that are characterized clinically by linear, smooth bands of atrophic-appearing skin that is reddish at first, then purple, and finally white. The most common sites are the thighs, buttocks, and breasts in girls (1). Histologically they are characterized by thinning of the overlying epidermis, with fine dermal collagen bundles arranged in straight parallel lines (2). In the early stages inflammatory changes are conspicuous. There is also elastolysis accompanied by mast cell degranulation, followed by activated macrophages that envelop fragmented elastic fibers (3). In the later stages the dermal collagen is layered in thin eosinophilic bundles, oriented in straight lines. The pathogenesis is unknown, but probably relates to changes in extracellular matrix components, including fibrillin, elastin, and collagen (4). However, the factors that lead to the development of striae are poorly understood. We report two cases of striae rubrae in 6-year-old monozygotic female twins.The twins were observed because of the sudden occurrence of reddish lesions on both thighs. The patients had been born preterm after 36 weeks of a monocorial twinning pregnancy from nonconsanguineous parents. Obstetric anamnesis was normal. The twins' past medical family history was unremarkable. Clinical examination showed typical striae rubrae on both their thighs and buttocks ( Figs. 1 and 2). The remainder of the skin examination excluded the presence of dysmorphic features, musculoskeletal deformities, including pectus excavatum, and tooth and hair changes. A mild hyperextensibility of distal joints and ligamentous laxity was noted. Both children were healthy and no stimulating factors, including systemic or topical steroid therapy, recent weight increase or loss, rapid growth, sports activities, infections, or trauma were identified.The parents refused permission for a skin biopsy. Hematologic and endocrinologic investigations, including evaluation of adrenocortical function (FSH, LH, prolactin, estradiol, 17-OH progesterone, testosterone, DHEA-S, androstenedione, ACTH, cortisol 8-16, 24-hour urinary cortisol and aldosterone, FT3, FT4, TSH), were normal. Renal, suprarenal, and ovarian ultrasonography were normal. Echocardiography excluded mitral valve prolapse, aortic dilation, and other valvular disorders.
