Immunosuppressive therapy has been reported to exacerbate or initiate the development of porokeratosis. Recently, with the widespread use of organ transplantation and immunosuppressive treatments, the incidence of porokeratosis has increased to 0.34~10.68% of patients who have undergone organ transplantation2
. The latency period between organ transplantation and the appearance of porokeratosis ranges from 4 months to 14 years2
. Clinically, immunosuppression-associated porokeratosis is more often characterized by multiple rather than single lesions3
. Most lesions are found on the legs, arms, and trunk1
. Although the exact type of porokeratosis has not always been specified, 50% of reported cases have been identified as DSP3
Recently, there have been many cases reported with atypical clinical characteristics of porokeratosis. In 1997, Herranz et al.4
reported that most of the cases were the mixed type of porokeratosis of Mibelli, and that DSP developed in 11 patients following kidney transplantation. In our case, the distribution and number of lesions were similar to those of DSP. However, based on the findings of well-defined keratinized lesions that were several centimeters in size and asymmetrical, a diagnosis of porokeratosis of Mibelli could not be ruled out. Therefore, our case was diagnosed as an atypical mixed type of porokeratosis.
Only 10 cases of porokeratosis after BMT have been reported in the English literature, and they are summarized in 2,5-9
. Most cases of porokeratosis following BMT were associated with leukemia. To date, immunodeficiency disorders associated with porokeratosis have been reported to include AIDS and precancerous blood disorders, as seen in our case3
. MDS is a disorder associated with abnormal B cell, NK cell, and CD4 (+) T cell function; therefore this bone marrow stem cell disorder can result in immunodeficiency.
Cases of porokeratosis following bone marrow transplantation reported in the English literature
It remains unclear whether the development of porokeratosis in our patient was affected by the immunodeficiencies associated with MDS or by the immunosuppressive treatment associated with the BMT. It is assumed, however, that the pathophysiology of porokeratosis is similar in either case3
. To explain this, several hypotheses have been proposed. First, loss of immunosurveillance caused by immunosuppression allows for the proliferation of abnormal keratinocyte clones, which leads to porokeratosis1,3
. To support this, Manganoni et al.10
provided evidence that the number and function of Langerhans cells were decreased and the expression of the HLA-DR antigen was reduced in the lesions. It has also been hypothesized that porokeratosis develops because of the higher rates of mitotic division in abnormal clones than in normal keratinocytes.
In most porokeratosis cases, treatment is not necessary. It has also been reported that lesions have spontaneously healed in immunocompromised patients after the primary malignancy was treated. In approximately 7~11.6% of patients, however, porokeratosis is associated with malignancies such as squamous cell carcinoma, basal cell carcinoma, and Bowen's disease. In particular, linear porokeratosis and porokeratosis of Mibelli are highly associated with these malignancies11
. Therefore, in immunocompromised patients who develop porokeratosis, the possibility of malignant transformation must be considered, and such cases must be followed by close observation. Histopathology is required to confirm malignant transformation in suspicious cases.