Dermatology: Practical and Conceptual Research Letter | Dermatol Pract Concept. 2023;13(4):e2023240 1 Dermoscopy Reveals Pseudopitting of the Nail in Psoriasis Ahu Yorulmaz1 1 Ankara Bilkent City Hospital, Department of Dermatology, Ankara, Turkey Key words: dermoscopy, nail psoriasis, salmon patches, pitting, pseudopitting Citation: Yorulmaz A. Dermoscopy Reveals Pseudopitting of the Nail in Psoriasis. Dermatol Pract Concept. 2023;13(4):e2023240. DOI: https://doi.org/10.5826/dpc.1304a240 Accepted: May 8, 2023; Published: October 2023 Copyright: ©2023 Yorulmaz. 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. Corresponding Author: Ahu Yorulmaz, Ankara Bilkent City Hospital, Department of Dermatology, Ankara, Turkey. Telephone: +90 312 552 60 00 Email: ahuyor©gmail.com Introduction Nail involvement in psoriasis is very common, with a re- ported lifetime incidence of up to 90% in all psoriatic [1]. Despite their high frequencies, nail alterations are usually neglected in psoriasis [2]. However, findings of nail psoriasis (NP) are usually specific, which allows a clinical diagnosis of psoriasis even if cutaneous lesions are absent [3]. Di Chiac- chio et al described a unique manifestation of NP, which they called pseudopitting. They presented a patient with psoria- sis, in whom pits were seen only above salmon patches (SP) [2]. Herein, cases of 3 patients with dermoscopic images of pseudopitting and a description of other features related to pseudopitting are presented. Case Presentation Some descriptive epidemiologic features were observed among the patients, including male predominance and a high frequency of accompanying arthritis (Table 1). One pa- tient (case #2), without arthritis, had a shorter duration of psoriasis. The psoriasis area and severity index scores of the patients were >10, except for one patient (case #4). Three patients had severe NP with a nail psoriasis severity index (NAPSI) score >50, whereas one patient had moderate NP with an NAPSI score >25. Figures 1 and 2 show dermoscopic images of the patients. Conclusions Nail bed-related findings are the characterizing features of NP because a significant component of the pathogenesis of psoriasis is driven through inflammatory angiogenesis [4]. Cases presented here share a similar clinical appearance, in which various nail bed-related findings are accompanied by pseudopitting or pitting. The image of case #4 does not demonstrate pseudopitting but gives an idea about the evolu- tion of pseudopitting. Several pits with salmon-colored cen- ters are located on the distal nail, which implies that these pits and SP represent different stages of a spectrum of the same pathological process, having different presentations based on their location (Figure 2B). SP is the counterpart of a psoriatic plaque in the nail bed, which results from focal nail bed parakeratosis. SP is a pathognomonic sign, whereas 2 Research Letter | Dermatol Pract Concept. 2023;13(4):e2023240 pitting, which occurs due to the foci of parakeratosis in the nail matrix, is a very characteristic but not a specific sign of NP [1]. Di Chiacchio et al demonstrated full-thickness para- keratosis of the nail plate over the nail bed in their patient. They suggested that pseudopitting shares similar pathogen- esis with pitting except for the defect of the location, which causes nail plate depression [2]. Not only the underlying causes but also the implications of pseudopitting are being questioned. Does the presence of pseudopitting signify other Table 1. Demographic and clinical profile of the patients Characteristics Case #1 Case #2 Case #3 Case #4 Age (years) 37 61 25 36 Sex M M M F Family history P A A P Psoriasis duration (years) 20 1 20 30 Accompanying arthritis P A P P Previous treatments Mtx, PhT PhT Mtx, PhT Mtx, biologics PASI 14.7 11.6 15 5.1 Total number of affected nails (F/T)ª 8/6 10/6 8/5 10/4 NAPSI 51 66 35 63 Nail findings DO, SP, RSL, LE, pitting DO, DHC, DBC, LE, SP, MWD, pitting SH, SP, nail bed red spots, DBC, LE, pitting DO, SP, SH, LE, DBC, nail bed red spots, pitting Current treatment Mtx PhT Mtx Biologic A = absent; DBC = dilated nail bed capillaries; DHC = dilated hyponychial capillaries; DO = distal onycholysis; ªF/T =fingernail/toenail; LE = longitudinal erythema of the nail bed; Mtx = methotrexate; MWD =multiple white dots; PASI = Psoriasis Area and Severity Index; PhT = Phototherapy; NAPSI = Nail Psoriasis Severity Index; RSL = red spot lunula; SH = splinter hemorrhages; SP = salmon patches. Figure 1. (A-I) Pits over SP (red lines), note peripheral white halos around some of the pits (A,C,E,F,H,I), SP with peripheral white halo (blue lines); nail bed red spots (green rectangles). (D) A pit over a RSL (purple line). (G): Note three zones of colors in SP (orange in the center, white in the middle and red in the outermost) (A-D, case #1; E-H, case #2, I, case #3). Research Letter | Dermatol Pract Concept. 2023;13(4):e2023240 3 meanings, such as having a more severe NP? Why did the patient of Di Chiacchio et al only manifest with pits over SP and not elsewhere on the nail plate? Why patients do pres- ent herein manifest with both pitting and pseudopitting? Do we fail to notice pseudopitting in everyday practice? These questions are unanswered yet; however, pseudopitting is ob- viously a pathognomonic finding of NP, which we should look for. References 1. Haneke E. Nail psoriasis: clinical features, pathogenesis, differ- ential diagnoses, and management. Psoriasis (Auckl). 2017;7:51- 63. DOI: 10.2147/PTT.S126281. PMID: 29387608. PMCID: PMC5774607. 2. Di Chiacchio N, André J, Haneke E, Di Chiacchio NG, Fonseca Noriega L, Ocampo-Garza J. Pseudo-pitting of the nail in psoria- sis. J Eur Acad Dermatol Venereol. 2017;31(7):e347-e348. DOI: 10.1111/jdv.14141. Epub 2017 Mar 1. PMID: 28129473. 3. Yorulmaz A. Dermoscopy: the ultimate tool for diagnosis of nail psoriasis? A review of the diagnostic utility of dermoscopy in nail psoriasis. Acta Dermatovenerol Alp Pannonica Adriat. 2023;32(1):11-15. PMID: 36945761. 4. Yorulmaz A, Aksoy GG. Dermoscopic Features of Nail Psoria- sis: Revisited. Skin Appendage Disord. 2022;8(5):389-398. DOI: 10.1159/000524109. PMID: 36161089. PMCID: PMC9485950. Figure 2. (A) Case #2: pits over SP (red lines); a white dot with a peripheral white halo (green line); (B) Case#4: multiple pits on ony- cholytic nail plate, note central salmon color and surrounding white rims (yellow triangle); SP (blue line); a wide SP on the lateral region of the nail plate (blue star); DO with peripheral erythema (red star); nail bed red spots with peripheral white halos (green rectangle); white patchy areas without central erythema (turquoise rectangle), note the lesions, which embody the characteristics of both a pit and a SP (turquoise circle).