INTRODUCTION

Perforating dermatosis (PD) constitutes a heterogeneous category of skin diseases featured by a papulonodular rash with transepidermal elimination of the dermal material. They are divided into the primary (or classic) or secondary forms [1]. Primary perforating dermatosis (PPD) encompasses four clinical subtypes: perforating folliculitis (PF), reactive perforating collagenosis (RPC), Kyrle disease (KD), and elastosis perforans serpiginosum (EPS) [1–3].

PD appears all over the world, with no racial selection. The highly rare onset in the childhood form of RPC is frequently familial, and childhood-onset EPS is occasionally familial. Although the exact inheritance pattern for both is incompletely elucidated, an autosomal dominant mode is suspected for some familial EPS cases. EPS affects males more often than females, with a ratio of ~4:1, whereas the sex distribution is nearly equal in RPC and acquired perforating dermatosis (APD). PF is recorded more commonly in females. In patients receiving maintenance hemodialysis, APD is seen in an estimated 4.5% to 11% [4].

Acquired perforating dermatosis is the secondary form of the disease [1]. It was introduced by Rapini in 1989 to describe PD affecting adult patients with chronic kidney disease (CKD), diabetes mellitus (DM), malignancy, hepatic, tuberculosis, neurodermatitis, atopic dermatitis and scabies [5–10].

The exact etiopathogenesis of PD is not well known. It is proposed that the PPD may be due to abnormal substances in the dermis, whether acquired or genetically altered. Alternative theories debate whether PD represents a unique pathologic process or is simply a result of mechanical exposure of the dermal materials [4].

Clinical and histologic manifestations are variable and may resemble any of the four PD subtypes, either alone or in combination [9]. In all PD, there is a plug of crusting or hyperkeratosis, with variable parakeratosis, depending upon the stage of the lesion. At the site of perforation, transepidermal elimination of both collagen and elastic fibers with inflammatory cells [4].

Thus, the aim of this study was to evaluate the clinical and histopathological features of PD that mimic prurigo nodularis, and to identify distinguishing features that help in their accurate diagnosis and differentiation from true prurigo nodularis.

PATIENTS AND METHODS

This was a case-series, descriptive study where thirteen cases with PD were seen during period from April 2021 to October 2025. Full demographic and clinical histories were taken. This work followed the Declaration of Helsinki Principles, and informed consent was taken from every patient.

A full medical record was obtained for every case, including demographic data (name, sex, age, occupation and address), patient’s chief complaint (e.g., itching, pain, or burning), course and duration of disease, age at onset, progression and evolution of the lesions, associated systemic diseases and symptoms, and past medical, surgical, family and medication history.

Physical examination was performed with particular attention to the distribution, sites, color, shape, size, and type of the cutaneous lesions. Biopsies for histopathological examination were taken from all cases using hematoxylin and eosin (H&E) stain. The clinically diagnosed cases with histopathological correlation were reviewed. The final diagnosis was established based on the patient’s history, clinical manifestations of the lesions, and pathological results. Routine laboratory examinations, including liver function tests, renal function tests, and blood glucose, were done.

RESULTS

Thirteen cases with PD were analyzed, their ages ranging from 10–55 years with a median of 32.5 years with 8 (61.53%) females and 5 (38.46%) males. The duration of the disease ranged from 3–15 years, with a mean of 7.66 years. The distribution of rash was nearly generalized but more intense on the limbs (Figs. 1 – 3). One female patient, her sister, had a similar disease. The type of rash was the papulo-nodular, well-defined, umbilicated, and excoriated type. Koebner phenomenon was noticed at the sites of scratching. All patients had severe itching with rash mimicking prurigo nodularis. After histopathological assessment that showed a perforating picture, such as epidermal invagination filled with plug of dermal contents and inflammatory cells (Figs. 1c, 2c, 3b), the diagnosis of PD was established.

	Figure 1: Twenty-year-old male patient with primary PD showing prurigo nodularis like perforating dermatosis affecting the upper limb and lower limb (a and b) and H&E-stained section of the same patient showing epidermal invagination filled with a plug of degenerated material (c) H&E, 10x).
	Figure 2: Forty-five-year-old female patient showing primary perforating dermatosis as multiple ulcerative papules with a central crust affecting the trunk (a and b). H&E-stained section of the same patient showing epidermal invagination filled with a plug of amorphous degenerated keratin, collagen and inflammatory debris with dense dermal infiltrate (c) H&E-stained section, 4x).
	Figure 3: Fifty-six-year-old male patient showing acquired perforating dermatosis with multiple prurigo nodularis like lesions affecting both lower limbs (a) and H&E-stained section of the same patient showing cup-shaped epidermal invagination filled with a plug of amorphous degenerated keratin, surrounded by acanthosis and inflammatory debris with dense dermal infiltrate (b) H&E-stained section, 4x).

Primary cases were established in 9 (69.23%) patients where no associated disease was observed, and these cases were children in 8 (88.88%) cases, their ages ranging from 5–15 years, with a mean of 8 years while one (11.11%) adult male, 45 years old. There were 7 (77.77%) females and 2 (22.22%) males.

Secondary cases with APD were observed in four (30.76%) adult patients with DM (Fig. 3). Their ages ranged from 25 to 55 years, with a mean of 37.5 years, with 3 (75%) males and 1 (25%) female. No association with other systemic diseases such as CKD, was identified, as confirmed by laboratory examinations.

DISCUSSION

PD constitutes a heterogeneous group of cutaneous disorders characterized by the elimination of dermal connective tissue through the epidermis [5].

Although the exact etiology of primary or idiopathic PD is still unclear, it is believed that transepidermal elimination of collagen is due to either genetic or acquired abnormalities of elastic or collagen fibers. Also, chronic rubbing or scratching in pruritic patients may lead to transepidermal elimination of dermal contents and causing PD [4]. The improvement in clinical symptoms after antipruritic treatment supports this thought. All of our patients mentioned itching as a presenting symptom and diagnosed initially as prurigo nodularis. Yet, as these patients did not respond to specific therapies, the diagnosis was reviewed again and perforating dermatosis was raised up as a diagnosis.

To our knowledge, this is the first clinicopathological study of PD that was reported in Iraq.

In this study, the mean of age in PPD in children group was 8 years with female predominance (77.77%), but these results could not be compared with other studies as the subtype of PPD was not determined and also, each subtype has different epidemiology making comparison not fully possible. While in APD the mean of age was 37.5% years with male predominance. This result was in line with the previously published study [11], while it was in contrast to another international study, in which APD was more commonly recorded in female patients, suggesting possible hormonal, demographic, or genetic differences between populations [12].

The distribution of skin lesions in our cases was generalized, but it was more intense on the extremities. The type of rash was the papulonodular, well-defined, umbilicated, and excoriated type. Also, crusts and excoriation were frequent presenting signs. While pruritus was mentioned in 100% of our cases, new cutaneous lesions appeared due to koebnerization following scratching. These findings are comparable with prior international studies on PD regarding patient age, lesion distribution, clinical morphology, concomitant symptoms, and Koebner phenomenon [13–16].

Two sisters in the current work had the same skin lesion, and this result increased the suspicion of the genetic role in the etiopathogenesis of PPD.

In this study, skin biopsy is essential to confirm the diagnosis of PD but sometimes more than one biopsy from different lesions and at several times with multiple serial sectioning are essential to reach a final diagnosis as it happened to one of our patients. However, the clinical and histopathological results of this PPD are not uniform and may resemble any of the four subtypes of PD. Often more than one form appeared in the same patient [12,17]. Therefore, in this study, we preferred to collect all clinical subtypes of PPD under the umbrella term primary perforating dermatoses.

Acquired perforating dermatosis typically manifests in patients with various systemic diseases, with DM and CKD being the most frequently associated diseases. In contrast, the majority of patients in this study with PD (9 cases, 69.23%) were otherwise healthy and demonstrated no systemic disease association, a finding consistent with previous research on PPD [18]. Consequently, further research is warranted to elucidate the pathogenic mechanisms underlying PD in otherwise healthy individuals.

A minority of cases (4 patients, 30.76%) were acquired and correlated with DM, a result comparable to another study where systemic disease associations, predominantly DM or CKD, were documented [13].

Lesions are usually self-limiting, but most of the time, recur with no tendency for spontaneous clearance. Management is mainly aimed at controlling itching. Topical steroids, retinoids, salicylic acid, cryotherapy, electrosurgical destruction, laser ablation, liquid nitrogen, photochemotherapy, UV-B phototherapy, systemic antihistamines, isotretinoin, methotrexate, and allopurinol are all suggested as a mode of therapy but with variable results [l,2].

CONCLUSION

Thirteen patients with PD were evaluated, all demonstrating the clinical features of prurigo nodularis. Nine cases were classified as PPD, while four cases were associated with DM and diagnosed as APD. Clinically, the lesions mimicked prurigo nodularis. It was found not easy to classify the primary forms into specific variants as it was difficult to clarify the type of the eliminated dermal materials, whether collagen, elastic, or follicular material. Consequently, the diagnosis was mostly either RPC or EPS. No spontaneous clearance was revealed in any of the cases; therefore, treatment remains particularly challenging and represents a significant therapeutic difficulty.

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