Graft-versus-host disease presenting along Blaschko lines: cutaneous mosaicism.

To the Editor: Graft-versus-host disease (GVHD) is a common and serious complication seen most often with bone marrow transplantation and peripheral blood stem cell transplantation. With these therapies, functional lymphoid cells are transferred from an immunocompetent donor into a nongenetically identical recipient, or “host.” Because of the allogeneic nature of these transplants, the transplanted lymphoid cells have a high potential to recognize and treat the host’s cells as foreign, and the resultant clinical and pathologic picture is that of GVHD. The primary organ systems affected in this immune response are the skin, gastrointestinal tract, and hepatobiliary system.1,2 Cutaneous manifestations are by far the most common.3 Although notable gains have been made in elucidating the causes, risk factors, and mechanisms that result in the clinical picture of GVHD, gaps in our knowledge and understanding still exist. Our patient represents a unique case of unilateral GVHD occurring along Blaschko lines, which has important implications for both recognizing and understanding the pathogenesis of GVHD. A 35-year-old woman was diagnosed with stage IV follicular lymphoma and received various chemotherapy regimens over the next 4 years. Unfortunately, her disease progressed despite treatment. At 39 years of age, she underwent a nonmyeloablative allogeneic peripheral blood stem cell transplantation from a single HLA-mismatched sibling. She was placed on prednisone and cyclosporine for immunosuppression. High-dose acyclovir prophylaxis also was initiated given her history of zoster affecting the right C3 dermatome. Successful engraftment was achieved, with molecular studies showing 100% of cells following transplantation were of donor origin. Restaging at 1 and 2 years following transplantation found her to be in complete remission. At 2 years following transplantation, she began a slow taper of immunosuppressive medications. She was successfully weaned off prednisone and continued to gradually reduce the cyclosporine dose. Toward the end of the cyclosporine taper 3 months later, she developed a pruritic eruption on the left proximal arm. She was seen in a bone marrow transplant clinic 4 weeks after the rash developed. On examination, she had multiple, violaceous, lichenoid papules coalescing into linear bandlike plaques. One plaque extended along the left upper arm and 2 others encircled the left hemithorax, respecting the midline. She was treated empirically for zoster with valacyclovir 1 g 3 times daily based on the presumed dermatomal distribution of the eruption. Despite treatment, the rash progressed, and she developed fever. Eight days later, she was admitted with concern for disseminated zoster (Figure). Viral tissue cultures and polymerase chain reaction analysis of the lesions were negative for varicella-zoster virus and herpes simplex viruses 1 and 2. Biopsies of skin lesions on the arm and trunk were both consistent with GVHD. Given the clinical history, characteristic lesion morphology, and distinct linear distribution along with Graft-versus-host Disease Presenting Along Blaschko Lines: Cutaneous Mosaicism