Ruxolitinib, a Janus kinase (JAK) inhibitor, selectively inhibits JAK1 and JAK2 and corrects aberrant JAK signaling in myelofibrosis. On the other hand, it has a severe immunosuppressive adverse effect, and thus varicella-zoster virus meningoencephalitis, molluscum, cytomegalovirus retinitis and herpes simplex virus 1 infection have been reported.1 Here, we describe our experience with the second reported case in the published work of iatrogenic Kaposi’s sarcoma in a patient with myeloproliferative disease who was treated with the JAK1/ 2 inhibitor ruxolitinib.An 81-year-old man had begun to receive ruxolitinib therapy (10 mg/day) for myelofibrosis 1 year earlier and had begun to develop lower leg edema and nodules 6 months after treatment initiation. At the first visit to our hospital, he presented with marked pigmentation and multiple black-brown papules, nodules and blood blisters (Fig. 1a,b). Initial laboratory studies revealed white blood cell and platelet counts of 29.3 9 103/lL and 87 9 103/lL, respectively, and hemoglobin, blood urea nitrogen, creatinine and lactate dehydrogenase concentrations of 9.6 g/dL, 27 mg/dL, 1.55 mg/dL and 267 U/L, respectively. Anti-HIV antibodies were negative. A histological examination of a left lower leg nodule revealed proliferating spindle-shaped cells in the dermis, with multiple vascular spaces (Fig. 1c). The proliferating tumor cells were positive for CD31, CD34 and human herpesvirus (HHV)8 latency-associated nuclear antigen 1 (Fig. 1d). Positron emission tomography/computed tomography Image-guided biopsy revealed no other lesions beyond the lower leg. The patient was diagnosed with iatrogenic Kaposi’s sarcoma attributed to ruxolitinib use. Ruxolitinib treatment was discontinued thereafter. However, the lesions did not improve, and the patient died 4 months later due to myelofibrosis-related progression of cytopenia and kidney damage.
Figure 1. (a,b) Clinical appearance of cutaneous lesions at the time of the initial visit. (c) Histopathological findings of a nodule from the lower leg. Hematoxylin–eosin staining biologically active building block revealed the proliferation of spindle-shaped cells, as well as many vascular cavities and leaking red blood cells around (original magnification 9400). (d) Immunohistochemistry revealed that the tumor cells were positive for human this website herpesvirus 8 latency-associated nuclear antigen 1 ( 9400).
Kaposi’s sarcoma can be classified as classic, iatrogenic, African endemic or AIDS-related. Iatrogenic cases are often improved by the tapering or withdrawal of immunosuppressant therapy.2 Classic and iatrogenic Kaposi’s sarcoma are generally rare, but arise frequently in some areas of the Mediterranean, Eastern Europe and the Middle East. In Japan, this condition arises frequently in Okinawa Prefecture, where the main island reports an incidence approximately 40-times higher than other areas of Japan, and especially Miyako Island, where the residents have high HHV8 infection rates comparable with those observed in the Mediterranean (15.4%) and an incidence of Kaposi’s sarcoma approximately 600-times higher than that elsewhere in Japan.3 The patient in our case resided on the main island of Okinawa.To our knowledge, ours is only the second reported case of iatrogenic Kaposi’s sarcoma during JAK inhibitor therapy. Both patients were taking ruxolitinib. In the first case, Kaposi’s sarcoma developed in the lower limb 7 years after ruxolitinib initiation for essential thrombocythemia but resolved 10 months after treatment discontinuation.4 In our case, Kaposi’s sarcoma developed 6 months after ruxolitinib initiation but did not improve despite discontinuation.In conclusion, as JAK inhibitors are administrated to treat various skin diseases, it is necessary to monitor patients for the development of Kaposi’s sarcoma, particularly in regions with high frequencies of HHV8 carriers.