Inherited reactive perforating collagenosis – A rare entity

INTRODUCTION

Perforating dermatoses are a group of disorders in which there is an elimination of dermal connective tissue through the epidermis. There are four known primary disorders based on the content eliminated – Kyrle’s disease (keratin), reactive perforation collagenosis (collagen), elastosis perforans serpiginosum (elastin), and perforating folliculitis (follicle).^[1,2] There are two distinct forms of reactive perforating collagenosis (RPC): Inherited form and acquired form. Skin biopsy confirms the diagnosis. Treatment includes management of the underlying disease, maintenance of pruritus, and keratolytic agents.

CASE REPORT

A 36-year-old man presented to our outpatient department with intense itchy papules and crusted nodules for the past 30 years over the face, bilateral elbows, and lower limbs. These lesions initially started as papules and then progressed to form crusted nodules [Figures 1-3]. For these complaints, he consulted a local physician and was given multiple courses of oral antibiotics, antihistaminics, topical antibiotics, and topical steroids with partial relief and had a relapsing and remitting course. There were episodes of intense itching followed by exacerbation of lesions for the past 6–8 months. He did not have any other known comorbidities. Based on clinical presentation, our differential diagnosis was perforating dermatoses and pustular pyoderma gangrenosum. His laboratory investigations and serological profile were within normal limits. To confirm the diagnosis, a skin biopsy was taken from the crusted nodule, and histopathology on lower magnification revealed inflammatory cell debris surrounded by acanthosis in epidermis [Figure 4]. On higher magnification, vertically oriented collagen fibers going into the epidermis are seen [Figure 5]. These findings were confirmed by Masson’s trichrome staining, which showed blue colored vertically oriented collagen fibers extending through the epidermis [Figure 6].

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Figure 1:

A 36-year-old man with papules and crusted nodules over the elbows.

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Figure 2:

Multiple well-defined crusted nodules and plaques over the legs.

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Figure 3:

Similar multiple well-defined crusted nodules and plaques over the thighs.

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Figure 4:

Histopathological examination of biopsy specimen from crusted plaque in low-power view showing inflammatory cell debris surrounded by acanthosis in epidermis as pointed by the black arrow (hematoxylin and eosin ×100).

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Figure 5:

Higher magnification demonstrating vertically oriented collagen fibers going into epidermis pointed by the black arrow (hematoxylin and eosin ×400).

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Figure 6:

Masson’s trichrome stain demonstrating vertically oriented collagen fibers going into the epidermis as pointed by black arrow (Masson’s trichrome stain ×400).

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Hence, the final diagnosis of inherited RPC was made. The patient was started on oral acitretin with topical keratolytics and showed significant improvement.

DISCUSSION

RPC is a rare skin disorder characterized by transepidermal elimination of altered collagen through the epidermis. Two patterns of RPC exist – the rare inherited form seen in children and the common acquired form seen in adults.^[3] Classic RPC is a genodermatosis that is inherited as an autosomal dominant or recessive trait. Fewer than 50 case reports of the inherited form of RPC exist in the world literature.^[4] The acquired form is more common and is often referred to as acquired perforating dermatosis, mostly associated with diabetes, hemodialysis, and internal neoplasia.^[5] Our patients did not have any systemic disease, indicating that systemic disease plays no role in the etiology of familial variety of RPC. Overexpression of transforming growth factor-beta 3 and extracellular matrix proteins may be seen.^[5] The basic defect seems to be a genetic abnormality of the collagen leading to its focal damage, which is then extruded as a result of necrolysis of the overlying epidermis. Trauma and cold induce the degeneration of collagen with thinning of epidermis in genetically predisposed individuals.

The lesions of inherited RPC usually begin in early childhood, and the lesions may become giant with increasing age.^[6] Our patients also developed lesions in early childhood, and the lesions became larger and more pruritic with increasing age.

Histopathologically, focal disruptions of the epidermis expelling collagen bundles and degenerated inflammatory cells occur in RPC.^[7] Our patients showed features that are consistent with RPC on histopathological examination, and Masson’s trichrome stain for collagen confirmed vertical bundles of collagen.

Lesions are usually self-healing without any treatment, but often recur. Treatment is mainly aimed at controlling the pruritus. Topical corticosteroids under occlusion, emollients, keratolytics, retinoids, systemic antihistamines, photochemotherapy, ultraviolet B phototherapy, liquid nitrogen cryotherapy, allopurinol, oral isotretinoin, methotrexate, and electrical nerve stimulation have been tried with varying success. Most lesions regress spontaneously in 6–8 weeks with hypopigmentation, scarring, or post-inflammatory hyperpigmentation. However, patients have a relapsing and remitting course of lesions throughout their lives.

Key messages: This is a rare case of inherited reactive perforating collagenosis without any systemic involvement, where histopathology aided in diagnosis.

CONCLUSION

Inherited variant of RPC is a rare skin disorder. Early diagnosis is essential to differentiate it from acquired form and other perforating dermatoses. Histopathology and special staining can help in confirming the diagnosis and aiding in management.