Pathology of Reactive Perforating Collagenosis

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Dermpath-India

Dr Sampurna Roy MD 2022

Dermatopathology Quiz Case: 209

Answer - Reactive Perforating Collagenosis

Perforating disorders of the skin are rare and it is often difficult to discriminate these conditions.

Reactive perforating collagenosis is a rare skin disease that is has a characteristic transepidermal elimination of altered collagen through the epidermis.

It occurs in two forms: an inherited form in childhood that is very rare and an acquired form in adulthood, more commonly found in patients with diabetes mellitus and end-stage renal disease.

Patterson proposed the following classification system:

(i) Perforation as an incidental histological finding;

(ii) Secondary perforation (Example: In granuloma annulare, pseudoxanthoma elasticum, and chondrodermatitis nodularis chronica helicis), and

(iii)Primary perforating dermatoses

Primary perforating dermatosis is a heterogeneous group of disorders characterized by transepidermal elimination of dermal components such as collagen, elastin, or fibrin.

There are 4 main subtypes based on both clinical and histologic factors:

1) Reactive perforating collagenosis (transepidermal elimination of collagen) ,

2) Elastosis perforans serpiginosa (transepidermal elimination of thickened elastic fibers),

3) Perforating folliculitis and

4) Kyrle disease (3 and 4 transepidermal elimination of keratin)

In 1989, Rapini et al coined the term acquired perforating dermatosis (APD) as a distinct entity. This disease usually develops in adulthood.

Acquired perforating dermatosis has been reported to occur in association with various diseases, but is most commonly associated with dialysis-dependent chronic renal failure or diabetes mellitus.

It may also be associated with hypertension, hepatitis, hypothyroidism, and chronic obstructive pulmonary disease.

Clinical and histological features of the disease are not uniform, and may resemble any of the four classic perforating disorders: elastosis perforans serpiginosa, reactive perforating collagenosis, perforating folliculitis or Kyrle's disease.

Clinically, acquired perforating dermatosis presents as local or generalized 1 to 10 mm papules with a central keratotic crater. Although lesions may present anywhere on the body, there is a slight predilection for the lower extremities.

The mean age of presentation is at the fourth to fifth decade of life, although any age may be affected with no gender predilection.

The duration of disease varies from a few weeks to 8 years.

The inherited form begins in infancy as papules located on the extensor surfaces of the hands, elbows, and knees, most likely after superficial trauma to the area. Reactive perforating collagenosis lesions then grow into larger, umbilicated papulonodules with central adherent keratin plugging. The lesions will most commonly resolve spontaneously in six to eight weeks, leaving behind a hypopigmented area or scar.The patient will most likely complain of pruritus of the lesions.

Histopathological features of reactive perforating collagenosis : Vertically oriented, cupping, or invagination of the epidermis most commonly is seen. Vertically oriented perforating bundles of basophilic collagen are present at the bases of the invagination of the epidermis with focal extrusions. A keratin plug most likely is found in the cupping of the epidermis. Histology is variable depending on the stage of the lesion. New lesions will show epidermal hyperplasia, degenerated basophilic collagen fibers with later lesions showing invagination of the epidermis with a keratin plug. The vertically oriented basophilic collagen fibers are highlighted with Verhoeff-Van Gieson staining, which stains the collagen fibers red.

The pathogenesis of reactive perforating collagenosis is still somewhat unclear, but it has been reported that trauma resulting from scratching may induce damage to the epidermis or dermal collagen.