Clinicopathological spectrum of pityriasis lichenoides: A case series of 19 patients

Abstract

BACKGROUND

Pityriasis lichenoides (PL) is considered a clinicopathologic continuum ranging from acute PL et varioliformis acuta to chronic PL chronica (PLC). Although histopathologic features are well defined, real-world clinicopathologic correlation and the adjunctive role of dermoscopy remain incompletely characterized.

AIM

To characterize the clinicopathologic spectrum of PL in a real-world adult cohort and to evaluate the adjunctive contribution of dermoscopy to disease assessment.

METHODS

We retrospectively reviewed 19 consecutive patients with biopsy-confirmed PL. Demographic data, clinical characteristics, histopathologic findings, treatment modalities, and outcomes were extracted from medical records. Dermoscopic features were analyzed in a subset of patients using a polarized handheld dermoscope. Descriptive statistical methods were applied.

RESULTS

PLC was the most frequent presentation, while a substantial proportion of patients exhibited overlapping clinicopathologic features, supporting the concept of a disease continuum. Dermoscopy, available in a subset of cases, revealed targetoid vascular patterns in acute and overlapping lesions, corresponding to histologic activity, whereas chronic lesions more commonly showed pigmentary background changes. Topical corticosteroids, narrowband ultraviolet B phototherapy, and low-dose methotrexate were the principal treatment approaches, with favourable clinical responses.

CONCLUSION

This case series highlights the dynamic and overlapping nature of PL. Dermoscopy may serve as a useful non-invasive adjunct to clinicopathologic correlation for assessing disease activity, while histopathologic confirmation remains essential.

Key Words: Pityriasis lichenoides; Pityriasis lichenoides et varioliformis acuta; Pityriasis lichenoides chronica; Dermoscopy; Clinicopathologic spectrum

Core Tip: Pityriasis lichenoides (PL) consists of overlapping clinicopathologic patterns rather than strictly separated PL et varioliformis acuta and PL chronica categories. This 19-patient series highlights the frequency of transitional forms and demonstrates how dermoscopy mirrors underlying histopathologic activity, offering a simple, noninvasive tool to distinguish acute from chronic lesions in routine practice. Recognizing these dynamic features may improve diagnostic accuracy and reduce unnecessary biopsies.

INTRODUCTION

Pityriasis lichenoides (PL) is increasingly regarded as a clinicopathologic continuum linking acute PL et varioliformis acuta (PLEVA) and chronic PL chronica (PLC), rather than as distinct entities[1]. Although its precise etiology remains unclear, histologic and immunologic evidence supports a T-cell-mediated inflammatory response, potentially triggered by infections or medications, with occasional reports of clonal T-cell expansions raising concerns about lymphoproliferative potential[2].

Despite well-established histopathologic criteria, real-world clinicopathologic correlation in adult patients remains limited, particularly in cases with overlapping or transitional features between PLEVA and PLC. Moreover, dermoscopic descriptions of PL are scarce and largely restricted to small case series, leaving the practical role of dermoscopy in routine disease assessment insufficiently defined[3,4].

In this context, we present a single-centre retrospective case series of 19 biopsy-confirmed PL patients, aiming to characterize the clinicopathologic spectrum of the disease and to illustrate the adjunctive contribution of dermoscopy in reflecting disease activity and supporting clinicopathologic correlation in clinical practice.

MATERIALS AND METHODS

Study design and patient selection

This retrospective observational case series included 19 consecutive patients diagnosed with PL at a single secondary dermatology centre between January 2022 and June 2025. Patients were identified through a retrospective review of electronic medical records and institutional pathology databases. All included cases had histopathologically confirmed PL based on punch biopsy and clinicopathologic correlation. No preselection was performed based on disease severity or treatment history.

Patients with clinicopathologic features suggestive of alternative diagnoses, including cutaneous T-cell lymphoma, were excluded following comprehensive clinical assessment and histopathologic evaluation by experienced dermatopathologists. Immunohistochemical staining and T-cell receptor gene rearrangement studies were not routinely performed, which is acknowledged as a limitation of the retrospective design.

Clinicopathologic classification

Cases were classified as PLEVA, PLC, or indeterminate PL spectrum based on combined clinical and histopathologic criteria. PLEVA was characterized by acute clinical presentation with necrotic keratinocytes, prominent erythrocyte extravasation, and dense inflammatory infiltrates. PLC was defined by a more chronic course with parakeratosis, milder interface dermatitis, and less pronounced epidermal necrosis. Cases showing overlapping or transitional clinical and histopathologic features were categorized as indeterminate PL spectrum, reflecting the recognized disease continuum.

Dermoscopic assessment

Clinical photographs and dermoscopic images, when available, were reviewed by a dermatologist. Dermoscopic examination was performed in a subset of patients using a polarized handheld dermoscope (DermLite DL5; × 10 magnification), primarily in contact mode. Dermoscopic findings were interpreted in conjunction with clinical and histopathologic features.

Data collection and statistical analysis

Demographic characteristics, clinical features, treatment modalities, and follow-up outcomes were extracted from electronic medical records. Descriptive statistical methods were used to summarize continuous and categorical variables. No inferential statistical analyses were performed due to the limited sample size and observational study design.

Ethics

The study was conducted in accordance with the ethical principles of the Declaration of Helsinki. As per institutional policy, formal ethics committee approval was not required for retrospective studies using fully anonymized clinical data. Written informed consent for the publication of anonymized clinical information, dermoscopic images, and histopathologic figures was obtained from all patients or their legal guardians.

RESULTS

Nineteen patients (14 women and 5 men; mean age 58 years, range 25-84) were identified during the study period. The lower limbs and trunk were the most frequently involved anatomical sites. Histopathologic examination commonly demonstrated parakeratosis, interface dermatitis, perivascular lymphocytic infiltrates, and erythrocyte extravasation, with necrotic keratinocytes predominantly observed in acute presentations.

Based on combined clinicopathologic assessment, 11 patients were classified as PLC, 2 as PLEVA, and 6 as indeterminate PL spectrum, reflecting overlapping clinical and histopathologic features. Dermoscopic evaluation was performed in a proportion of patients representing acute, chronic, and indeterminate spectrum presentations. Acute and overlapping lesions most frequently exhibited targetoid vascular patterns, whereas chronic PLC-like lesions were characterized by pigmentary background changes with fewer vascular structures.

Most patients were treated with topical corticosteroids, with or without oral antihistamines. Narrowband ultraviolet B phototherapy was administered in four patients, and low-dose methotrexate was used in six patients, occasionally in combination with other treatment modalities. Representative clinical and dermoscopic findings are illustrated in Figure 1.

Figure 1 Clinicodermoscopic spectrum of pityriasis lichenoides. A: Acute-spectrum presentation with multiple erythematous-brown papules, several showing central crusts at different evolutionary stages on the extremity; B: Dermoscopy of an acute-spectrum lesion showing a central reddish-brown amorphous/crusted area with a peripheral white collarette of scale and dotted/glomerular vessels; C: Chronic papular presentation pityriasis lichenoides chronica C-like (PLC-like) with fine scaling on the back; D: Dermoscopy of a PLC-like lesion showing a central brown-crusted plug over a yellow-brown structureless background with peripheral fine scale and sparse vessels. These findings align with recent dermoscopic descriptions and may aid recognition without biopsy.

The median disease duration at presentation was 3 years (range, 1 month-12 years), with longer disease courses observed in patients classified as PLC and indeterminate PL spectrum compared with those with PLEVA (Table 1).

Table 1 Demographic and clinicopathological features of 19 patients with pityriasis lichenoides.

Classification	n (%)	Mean age (years)	Female (%)	Disease duration, median (range)
PLC	11 (58)	56	82	3 years (1-12 years)
PLEVA	2 (11)	79	50	0.5 year (1 month-1 year)
PL spectrum (indeterminate)	6 (32)	53	67	3.5 years (6 months-9 years)
Total	19	57.6 (25-84)	74	3 years (1 month-12 years)

Data are presented as n (%) unless otherwise indicated. Disease duration at presentation is reported as median (range). Pityriasis lichenoides spectrum, indeterminate clinicopathological cases not classifiable as pityriasis lichenoides chronica or pityriasis lichenoides et varioliformis acuta. PL: Pityriasis lichenoides; PLC: Pityriasis lichenoides chronica; PLEVA: Pityriasis lichenoides et varioliformis acuta.

DISCUSSION

This single-centre cohort underscores the clinicopathologic continuum of PL, encompassing both PLEVA and PLC[5]. Approximately one-third of patients in our series exhibited overlapping or indeterminate features, supporting previous observations that PL represents a dynamic spectrum rather than discrete clinicopathologic entities[6].

Dermoscopy provided a useful, non-invasive reflection of histopathologic activity. In acute and overlapping lesions, central reddish-brown crusts surrounded by a white collarette and a peripheral vascular ring composed of dotted, linear-irregular, or glomerular vessels corresponded to the polymorphous “targetoid” pattern described in recent reports[7,8]. These vascular features likely reflect papillary dermal capillary dilation and microhemorrhage associated with active inflammation. In contrast, chronic PLC-like lesions demonstrated brown-crusted plugs, yellow-brown structureless areas, and sparse dotted vessels, consistent with residual or post-inflammatory changes.

Recognition of these dermoscopic patterns may support disease staging and assist clinicopathologic correlation in routine practice, while histopathologic confirmation remains essential. From a therapeutic perspective, the use of topical corticosteroids, narrowband UVB phototherapy, and low-dose methotrexate in our cohort is consistent with existing literature, highlighting their efficacy and tolerability across the PL spectrum[9,10].

Overall, integrating dermoscopy with clinical and histopathologic assessment may enhance diagnostic confidence and facilitate individualized, stepwise management strategies for this chronic relapsing disorder.

CONCLUSION

This study highlights the overlapping and transitional features of PL across its acute and chronic forms, supporting the concept of a clinicopathologic disease continuum. Dermoscopy may serve as a practical, non-invasive adjunct to clinicopathologic correlation for assessing disease activity, particularly in acute and overlapping presentations.

Limitations of this study include its retrospective design, the relatively small sample size, and the absence of dermoscopic documentation in all patients. In addition, the lack of routine immunohistochemical or molecular studies represents an inherent limitation of the study design. Future prospective studies with standardized dermoscopic assessment and ancillary investigations are warranted to further validate these findings.

ACKNOWLEDGEMENTS

The author would like to thank the staff of the Dermatology Clinic at Gaziantep Nizip State Hospital and the dermatopathologists at Gaziantep 25 Aralık State Hospital for their contributions to both the diagnostic evaluation and clinical management of the cases.