dermatologic disorders
Parapsoriasis
Diagnosis of Parapsoriasis
Clinical evaluation Sometimes biopsy and genetic and molecular testing to rule out cutaneous T-cell lymphoma (CTCL) Diagnosis of parapsoriasis is based on clinical appearance and distribution. Biopsy can be helpful if there is concern for CTCL (see Diagnosis ), but otherwise the diagnosis of parapsoriasis is clinical. Histologic findings may not be classic for CTCL, but immunophenotyping analysis and T-cell gene rearrangement studies can be done to identify a T-cell clone if it exists. Differential diagnosis of small-plaque parapsoriasisincludes the following: Cutaneous T-cell Lymphomas (CTCL) None Nummular Dermatitis None Pityriasis Rosea None Secondary syphilis None Subtypes of Psoriasis None Pityriasis Lichenoides None It is most important to rule out CTCL because early CTCL can be hard to distinguish clinically from small-plaque parapsoriasis. Biopsy is informative and can be used to distinguish between small- and large-plaque psoriasis. Differential diagnosis of large-plaque parapsoriasisincludes the following: CTCL Psoriasis None Contact Dermatitis None 