Track

Case Reports

Abstract

We report a case of a CD30 positive cutaneous lymphoproliferative disorder presenting with
sterile pustules mimicking pustular psoriasis. A 79-year-old man without a history of malignancy
or immunosuppression had a two-year history of erythematous plaques and nodules on the trunk,
axillae, and groin studded with pustules and unresponsive to Risankizumab. Punch biopsy
showed intraepidermal pustules, scattered epidermotropism and folliculotropism, and a brisk
band-like lichenoid and perivascular atypical lymphohistiocytic infiltrate. Immunohistochemistry
demonstrated diffuse strong CD3, CD7 and CD30 positivity with a largely unaltered CD4 to CD8
ratio. CD5 was retained. ALK was negative. Ki67 highlighted 20-30% of the infiltrate.
Microorganisms were not identified on Gram, GMS, and PAS. The findings supported a CD30
positive lymphoproliferative disorder within the spectrum of mycosis fungoides, ALK-negative
anaplastic large cell lymphoma (ALCL), or lymphomatoid papulosis. Pustular mycosis fungoides
and anaplastic large cell lymphoma are rare, but may represent a more aggressive course or in
the case ALCL may represent potential aggressive systemic disease. These must be differentiated
from lymphomatoid papulosis, which can also manifest with pustular lesions composed of CD30
positive atypical lymphocytes. This case underscores that prominent pustulation in CD30
positive disease warrants early biopsy with immunophenotyping, exclusion of infection and acute
generalized exanthematous pustulosis, and consideration of lymphoma directed therapy, as
pustulation may signal a higher risk of systemic involvement or transformation and necessitates
close surveillance.