Hypopigmented parapsoriasis en plaque, a new, overlooked member of the parapsoriasis family: a report of 34 patients and a 7-year experience.

Abstract

In the past 7 years we have extensively studied an uncommon hypopigmented disorder that, apart from hypopigmentation, showed many common features with parapsoriasis en plaque (PSEP), both clinically and histopathologically. We sought to verify whether this disorder should be considered a hypopigmented variant of PSEP and thus be referred to as hypopigmented PSEP. A total of 34 patients presenting with this peculiar hypopigmented disorder were included (2003-2010). Patients were subjected to a predesigned algorithm excluding all possible differential diagnoses of hypopigmented lesions. Our findings indicated that this disorder can be diagnosed as hypopigmented PSEP. These findings included: (1) exclusion of all other disorders causing similar hypopigmented lesions; (2) shape and size of the lesions being very similar to those of classic small PSEP (small-plaque parapsoriasis [SPP]); (3) similar distribution of the lesions (trunk, proximal upper and lower limbs) to the classic PSEP; (4) digitiform extensions of most the lesions (70.5% of our patients) as in SPP; (5) absence of itching as in PSEP (SPP type); (6) good response to narrowband ultraviolet B in 76.4% of the patients (n = 26); and (7) during follow-up 5 patients (14.7%) converted into hypopigmentd mycosis fungoides. A limitation in our study is that we did not perform clonal T-cell receptor gene rearrangement because of limited resources. Based on our findings we believe that this hypopigmented disorder is a well-defined new variant of the PSEP family that shows, apart from the hypopigmentation, all the features of PSEP, particularly the SPP variant, and accordingly could be referred to as hypopigmented PSEP.