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Background
Acquired perforating disorder is a disorder of keratinization that is associated with diabetes,mellitus, and uremia. The perforating disorders of the skin are a group of diseases characterized by trans-epidermal (which is the measurement of how much water passes from the body to the epidermal layer of skin) elimination of material from the upper dermis and are classified histopathologically according to the type of epidermal disruption and the nature of the eliminated material. An acquired perforating dermatosis has been found to be in association with renal failure and is commonly seen where the underlying cause of renal failure is diabetic nephropathy. Perforating disorders of the skin can be obtained from a single pathologic entity. Each of the classic perforating disorders of skin, including elastosis perforans serpiginosa, perforating folliculitis, reactive perforating collagenosis, Kyrle's disease, and perforating disorder of uremia, have been shown to extrude collagen, elastin, and related extracellular matrix components through the epidermis.

Mechanism
Initially described by Kyrle in 1916 as hyperkeratosis follicularis, acquired perforating disorder, the pathogenesis is unknown, acquired perforating collagenosis has been found to be associated with types I and II diabetes mellitus in as many as 90 percent of cases as well as with chronic renal disease. One proposed mechanism involves increased levels of fibronectin, which is an adhesive glycoprotein that forms part of the extracellular matrix, in the sera and skin of patients with predisposing diseases (diabetes mellitus, uremia, and inborn errors of fibroblast synthesis, such as osteogenesis imperfecta and Marfan disease).

Symptoms
Symptoms of the acquired perforating disorders consist of flesh-colored, circular shaped papules  as large as 10 mm in diameter that can also be scaly and yield a coiled hair. They have a keratinous plug. There are lesions that may occur in a linear configuration, exhibiting the Koebner phenomenon. Residual scarring may be seen from previously healed lesions.

In the inherited form, painless 1 to 6 mm diameter keratotic papules develop on the extensor surface of the hands, the elbows, and the knees following superficial trauma. The lesions start off as pin-sized lesions that over 3-5 weeks grow to a papule of about 6mm. These resolve spontaneously in 6-8 weeks leaving residual minor scarring. Lesions recur throughout life into adulthood. In some cases, cold weather conditions can trigger the recurrence of lesions.

In acquired perforating disorders, the lesions  can also develop on the trunk and extremities and are associated with itching. Lesions are often but not necessarily related to superficial trauma.

Diagnosis
To diagnose APD, renal function studies, including urinalysis, serum creatinine, and creatinine clearance, can be performed to assess for  possible underlying renal disease, if affirmed by family history and/or physical findings. Test blood glucose levels to evaluate for possible diabetes mellitus can also be performed as well as a skin biopsy. The biopsy is carried out when uncertainty about the nature of an eruption exists, to single out APD or another disorder. It also helps to decipher perforating folliculitis from other inflammatory disorders of the hair follicle, such as irritant folliculitis, acneiform folliculitis, or infectious folliculitis histopathologic findings. If the perforating folliculitis are focal, they can be missed if a skin biopsy is sectioned incompletely, resulting in a pathology report being returned with a nonspecific diagnosis.This can be avoided by  a small punch biopsy that completely encompasses the lesion.

There are many other disorders characterized by papules or nodules with central keratotic plugs and crusts. The deep penetration of the keratotic plugs, the size and irregularity, the age of onset and the distribution of lesions should aid in the diagnosis. It is also essential to examine and test for any underlying conditions such as diabetes, liver and renal disease.

Causes and Prevention
The underlying cause of reactive perforating collagenosis is unknown, but an abnormal response to superficial trauma such as scratching may be involved. Papules have been reported following scratches, acne spots, insect bites, and scabies. The acquired form of reactive perforating collagenosis may occur in association with chronic renal failure, often in a patient with underlying diabetes. In both the United Kingdom and the United States, the prevalence of this disorder in patients on dialysis is approximately 10%.

The acquired form of reactive perforating collagenosis also can occur in association with other nephropathies without diabetes. Acquired reactive perforating collagenosis has been reported in association with hypothyroidism, hyperparathyroidism, and liver dysfunction, and dermatomyositis.

The childhood form of reactive perforating collagenosis is inherited. The mode of inheritance is unclear but some reports of affected families show autosomal dominant inheritance, autosomal recessive inheritance, and sporadic cases.

Evidence suggests a pathologic role for many coiled hairs being an origin of the disorder. Factors that may promote coiling of hairs include follicular hyperkeratosis or contact dermatitis (eg, resulting from formaldehyde in clothing).

Incidence

Out of the perforating diseases in the United States it is not known precisely, although the disorder is not uncommon. In Detroit, Michigan, 50 cases were reported during a 2-year period in the early 1970s, although this observation was followed by a declining incidence of new cases.

Mortality/Morbidity
Morbidity is associated with the cosmetic appearance of lesions and the pruritus that occasionally accompanies them. Although cutaneous disease is insignificant, substantial morbidity or mortality rates can be seen in association with the primary underlying diseases, such as diabetes mellitus or chronic renal failure.

Sex/ Race
Occurs equally in males and females; no sex predilection has been reported. Although generally no ethnic predilection has been identified, 1 study found a higher incidence of Kyrle disease in chronic renal failure among African American individuals.

Age
More common in the second through fourth decades of life.

Treatment and Prognosis
Since some cases of perforating diseases are associated with systemic disorders (eg, diabetes mellitus, chronic renal failure), direct therapeutic efforts towards the underlying condition in these patients. In a case report of perforating folliculitis in a patient with diabetes mellitus and phrynoderma, the skin lesions resolved with correction of the vitamin A deficiency. Soothing antipruritic lotions may be helpful for patients in whom itching is a significant problem. UV-B irradiation also may be of general benefit in the control or amelioration of pruritus.

Assessing treatments for perforating folliculitis is difficult. Although the condition is not uncommon, controlled therapeutic studies are not available. Unsuccessful treatments have included oral beta-carotene, keratolytics, anti-acne therapies, and topical corticosteroids.

Tretinoin 0.1% cream has cleared some perforating folliculitis lesions but has not prevented the development of others. A case of successful treatment using 13-cis -retinoic acid has been reported.[25]

Further outpatient dermatologic care may be required for ongoing management of the perforating folliculitis when lesions persist, spread, or become resistant to therapy. Follow-up care may be necessary for complications related to therapy. Outpatient internal medicine care may be indicated for management of any underlying medical conditions, such as chronic renal failure, hypertension, diabetes mellitus, or atherosclerotic cardiovascular disease.

Recent Research

 * Acquired Perforating Dermatosis in Patients with Chronic Renal Failure and Diabetes Mellitus This study looked at clinical and histopathological features of APD, and evaluated the role of scratching in its pathogenesis. The purpose of this study was to clarify the clinical and histopathological features of APD, and evaluate role of scratching in the pathogenesis of APD. Some findings were These data showed that scratching appear to play a critical part in the pathogenesis of APD.


 * Kyrle Disease and Acquired Perforating Collagenosis Secondary to Chronic Renal Failure and Diabetes Mellitus This study focuses on discussingthe mechanisms of transepidermal elimination and the classification of perforating disorders.