Acquired reactive perforating dermatosis within poikiloderma of Civatte elicited by narrow-band UVB therapy for psoriasis

Primary perforating dermatosis group of skin diseases encompasses hyperkeratosis follicularis et parafollicularis in cutem penetrans (Kyrle's diseases), elastosis perforans serpiginosa and reactive perforating dermatoses (syn. collagenosis) with hereditary and acquired forms.¹ Histopathologically are characterized by the elimination of collagen or elastin fibers through the epidermis.²

A 64-year Caucasian female with a Fitzpatrick type III skin type received treatment for an acute onset of guttate psoriasis with 311 nm NB-UVB therapy (Medisun 2800, Schulze & Bohm, Germany) three times per week and topical betamethasone/calcipotriol foam once daily. She reported phototherapy treatment for psoriasis twenty years earlier. Her medical history was otherwise unremarkable.

After nine sessions of NB-UVB therapy (cumulative dose 5800 mJ/cm²) the psoriatic lesions were remitting (Figure 1a). Yet, multiple intensely itchy partly coalescing crusted papulopustules up to 7 mm diameter with a keratotic center appeared on poikilodermatous background covering the V-area and the intermammary cleft (Figure 1b). Subsequently, the affected area was light-protected during UV irradiations and fusidic acid 2% cream was applied twice daily under the provisional diagnosis of staphylococcal impetigo. Bacterial swab results were negative while the concurrent laboratory work up showed only hyperlipidemia without diabetes or impaired renal function. A lesional skin biopsy from the V-area revealed a cup-shaped epidermal erosion filled with a basophilic plug of keratin, inflammatory debris, and expelled collagen and elastic fibers, findings compatible with ARPD (Figure 2). The differential diagnosis also included erosions secondary to the intense itching, yet ARPD is typical characterized by a dense central keratotic plaque rich of debris and expelled dermal fibers as seen here. The PAS stain showed a missing basement membrane (BM) at the site of the erosion without any hyphae, spores or gram-positive bacteria.

The constellation of the clinical, laboratory and pathology findings support the diagnosis of an ARPD associated with guttate psoriasis on a chronic solar poikiloderma background (Civatte). Four weeks later the symptoms and clinical signs for both the ARPD and psoriasis had subsided (Figure 1c) and the patient opted to discontinue all therapeutic interventions.

ARPD arose unexpectedly within a psoriatic background, a combination that has been sparsely reported in literature. Actually, a PubMed search (23 September 2024) up to 1980 under the terms ‘perforating dermatosis’ OR ‘perforating collagenosis’ AND ‘psoriasis’ returned 32 articles in which only three patients are reported with the combination of ARPD and psoriasis.^{3, 4} Two of the patients were of dark skin phototype (Philipino and Indian)^{3, 4} with one receiving hydrochlorothiazide for hypertension, an established photosensitizer that can accumulate in the BM. None of the aforementioned cases reported chronic sun damaged or received phototherapy. Therefore, the present case stands out because NB-UVB is also a proposed therapeutic option in perforating dermatoses.^{3, 5}

In perforating dermatoses, damage to the BM is the inciting event leading to altered composition of BM-associated laminins⁶ and UV can further impact the integrity of both.⁷ Furthermore, the milieu of cytokines in both UV-radiated skin⁸ and ARPD⁹ is characterized by increased production of transforming growth factor isoforms and matrix metalloproteases, suggesting a combined BM-damaging mechanism. These findings support the idea that in this case the psoriatic lesions and NB-UVB could have jointly triggered ARPD.^{9, 10} However, this suggestion does not adequately explain the negligible number of reported cases of psoriasis and ARPD. We suggest that in our case the underlying poikiloderma of Civatte and an associated BM damage could have acted as predisposing factors, which assisted the synergistic action of UV-light and psoriasis to co-trigger ARPD as previously.^{3, 4}

In conclusion, the presented case expands the clinical setting of this condition and underscores the possible existence of an ARPD subgroup triggered by therapy in conjunction to underlying predisposing diseases.

G. Gaitanis: Conceptualization; writing of the original draft. L. Feldmeyer: Writing—review and editing. R. Wolf: Writing—review and editing.

The authors declare no conflict of interest.

All patients in this manuscript have given written informed consent for participation in the study and the use of their deidentified, anonymized, aggregated data and their case details (including photographs) for publication. Ethical approval: Not applicable.