Answer of Dermatopathology Case 51

Prurigo Nodularis

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Abstract:

Prurigo nodularis: systematic analysis of 58 histological criteria in 136 patients.J Cutan Pathol. 2010 May;37(5):578-86. Epub 2009 Nov 30.
BACKGROUND: To date, there has been no systematic investigation of the detailed histological features of prurigo nodularis (PN) in a large cohort of patients. METHODS: This retrospective study includes skin biopsies of 136 patients (63 males, 73 females; mean age: 58.38 years) with PN. RESULTS: Highly characteristic for PN is the presence of thick compact orthohyperkeratosis; the hairy palm sign (folliculosebaceous units in nonvolar skin in conjunction with a thick and compact cornified layer, like that of volar skin); irregular epidermal hyperplasia or pseudoepitheliomatous hyperplasia; focal parakeratosis; hypergranulosis; fibrosis of the papillary dermis with vertically arranged collagen fibers; increased number of fibroblasts and capillaries; a superficial, perivascular and/or interstitial inflammatory infiltrate of lymphocytes, macrophages and, to a lesser extent, eosinophils and neutrophils. For comparison, histological findings in 45 patients (18 males, 27 females; mean, 55.64 years) with lichen simplex (LS) were studied. PN and LS, both of them scratch-induced, had 50 of 58 (86.2%) histological features in common. CONCLUSIONS: PN revealed a characteristic histological pattern. Absence of pseudoepitheliomatous hyperplasia or nerve fiber thickening, however, does not rule out the histological diagnosis of PN. A correlation of clinical and histological findings is necessary to reliably distinguish between PN and LS.

Prurigo nodularis in a 9-year-old girl.Clin Pediatr (Phila).2009 Jan;48(1):93-5. Epub 2008 Jul 22.
A 9-year-old African-American female with a known history of atopic dermatitis presented for evaluation of an intensely pruritic nodular rash on both upper and lower extremities, buttocks, and lower abdomen for more than 1 year. The patient had been treated with several medium-potency topical steroids and antipruritics without appreciable improvement. After considering and excluding other differential diagnoses, the diagnosis of prurigo nodularis (PN) in association with atopic dermatitis was made. Prurigo nodularis usually occurs in middle-aged and older persons and is rarely seen in the pediatric population. The onset of PN in the case presented is considerably earlier than what has been described in literature. The etiology of the disorder is unknown. The management of prurigo nodularis is usually challenging for both patients and treating physicians. Frequently, combinations of several medications or modalities are used in an attempt to control disease activity. Overall, PN is a benign condition in children, particularly when it is associated with atopic dermatitis. It does not increase mortality; however, it can cause significant morbidity in untreated patients.

Prurigo nodularis: a benign dermatosis derived from a persistent pruritus. Acta Dermatovenerol Croat.2008;16(1):38-44.
Prurigo nodularis (PN) is a benign neurodermatitis of unknown etiology characterized by firm, hyperkeratotic pruritic nodules most commonly localized symmetrically on the bilateral extensor lower extremities. PN represents a primary dermatological condition or a dermatological manifestation of repeated traumatic manipulation secondary to chronic pruritus. One must consider underlying causes of pruritus, which may include psychiatric disorders and internal disease. Given its chronicity and relapsing nature, treatment of PN can be challenging. Interruption of the itch-scratch cycle is difficult; long term prognosis remains guarded.

Prurigo nodularis: a review.Australas J Dermatol.2005 Nov;46(4):211-18; quiz 219-20.
Prurigo nodularis is a chronic condition characterized by a papulonodular pruriginous eruption of unknown aetiology. This condition is a difficult disease to treat and causes frustration to both the patient and the treating doctor. A variety of systemic conditions have been reported to be associated with prurigo nodularis. The mechanism by which these disorders may trigger prurigo nodularis is unknown. Nerve growth factor has been implicated in the pathogenesis of prurigo nodularis. Calcitonin gene-related peptide and substance P immunoreactive nerves are markedly increased in prurigo nodularis when compared with normal skin. These neuropeptides may mediate the cutaneous neurogenic inflammation and pruritus in prurigo nodularis. Topical or intralesional glucocorticoids are the treatment of choice. Other topical treatments such as topical vitamin D3, and topical capsaicin have also been reported to be effective. Oral treatments such as cyclosporin and thalidomide have been shown to improve both appearance of the skin and pruritus. We review the clinical features, associations, pathology, pathogenesis and treatment of prurigo nodularis.