Dermatology: Practical and Conceptual Research Letter | Dermatol Pract Concept. 2022;12(2):e2022088 1 Natalizumab-Induced Pustular Psoriasis of Palms and Soles Bengisu Ozarslan1, Teresa Russo2, Giuseppe Argenziano2, Vincenzo Piccolo2 1 Dermatology Unit, Doku Medical Center, Istanbul, Turkey 2 Dermatology Unit, University of Campania Luigi Vanvitelli, Naples, Italy Key words: natalizumab, psoriasis, pustular, palmo-plantar Citation: Ozarslan B, Russo T, Argenziano G, Piccolo V. Natalizumab-Induced Pustular Psoriasis of Palms and Soles. Dermatol Pract Concept. 2022;12(2):e2022088. DOI: https://doi.org/10.5826/dpc.1202a88 Accepted: September 18, 2021; Published: April 2022 Copyright: ©2022 Ozarslan et al. This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial License (BY-NC-4.0), https://creativecommons.org/licenses/by-nc/4.0/, which permits unrestricted noncommercial use, distribution, and reproduction in any medium, provided the original authors and source are credited. Funding: None. Competing interests: None. Authorship: All authors have contributed significantly to this publication. Corresponding author: Vincenzo Piccolo, MD, c/o II Policlinico, building 9, first floor, via Pansini 5 - 80131 Napoli, Italy. E-mail: piccolo.vincenzo@gmail.com Introduction Psoriasis and multiple sclerosis (MS) are both autoimmune T-cell mediated diseases that share a possible common ge- netic linkage [1]. Natalizumab is a recombinant humanized monoclonal antibody targeting the cell adhesion molecule α4 integrin and is labeled to treat MS. It is known that bi- ological agents induce cutaneous adverse drug reactions. Although there is not a defined link between natalizumab and psoriasis, there are case reports describing a possible re- lationship [2]. Here, we report on a patient with MS who developed pustular psoriasis of palms and soles after natali- zumab treatment. Case Presentation A 50-year-old woman presented with multiple millimetric pustules and scaling sited on erythematous plaques on the palms and soles (Figure 1A). Personal and familiar history for psoriasis was negative. She has been treated with natal- izumab for 6 months for MS. Dermoscopy revealed yellow globules and crusts along with the dotted vessels (Figure 1B). The patient was diagnosed with pustular psoriasis of palms and soles. Discussion Data on whether natalizumab can induce or aggravate psori- asis are limited. In literature, 2 of the cases developed plaque psoriasis while 1 patient had new-onset psoriatic arthritis during natalizumab treatment. Family history of psoriasis was positive in all patients. One patient affected by mild pso- riasis had a severe flare-up after several natalizumab infu- sions [2]. Our patient, on the other hand, differs from those cases due to the absence of family history and the develop- ment of localized pustular psoriasis. Although there are pieces of evidence showing com- mon pathophysiological pathways in psoriasis and MS, it has been observed that treatment of one condition did not provide a parallel improvement in the other one. T helper 17 (Th17) cells are involved in the inflammation stage of both disease [1]. The pathophysiological mechanism between 2 Research Letter | Dermatol Pract Concept. 2022;12(2):e2022088 psoriasis and natalizumab remains unclear but natalizumab has been associated with paradoxical activation of autoim- mune disorders by pathologically stimulating the production of IL17 and increased activation of Th17 cells [2]. Conclusions We highlight that a new onset of palmoplantar pustular pso- riasis may also be a rare side effect of natalizumab. There is not enough data yet to make a recommendation regard- ing the consideration of psoriasis history in the patient or in the family when deciding for natalizumab treatment. More research is needed to understand the relationship between natalizumab and psoriasis. References 1. Kwok T, Loo WJ, Guenther L. Psoriasis and multiple sclerosis: is there a link? J Cutan Med Surg. 2010;14(4):151-155. DOI: 10.2310/7750.2010.09063. PMID: 20642982. 2. Lambrianides S, Kinnis E, Leonidou E, Pantzaris M. Does na- talizumab induce or aggravate psoriasis? A case study and review of the literature. Case Rep Neurol. 201818;10(3): 286-291. DOI: 10.1159/000492891. PMID: 30323758. PMCID: PMC6180259. Figure 1. (A) Multiple pustules and crusting over the palm. (B) Dermoscopic image demon- strates yellow globules and crusts along with the dotted vessels.