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Pathology of Prurigo Nodularis                   

Dr Sampurna Roy MD

"Skin lesion characterized by Pseudo-Epitheliomatous Hyperplasia"

Dermatopathology Quiz Case No. 51

Diagnosis: Prurigo Nodularis

March  2016

Dr Sampurna Roy  MD

Consultant  Histopathologist (Kolkata - India)


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Prurigo nodularis is an uncommon lesion that presents as extremely pruritic nodules with a  wide anatomical distribution but particularly on extensor aspects of limbs.

Often lesions are multiple but solitary nodules can occasionally occur.

Lesions tend to be symmetrical and are associated with excoriations.

Females are more often affected than males.

Many authors consider this condition as part of the spectrum of lichen simplex.

Atypical mycobacteria may be a contributing factor in prurigo nodularis.

Microscopic features: 

Histopathology reveals psoriasiform hyperplasia or pseudo-epitheliomatous hyperplasia  ;

Marked hyperkeratosis with hypergranulosis and focal parakeratosis ;

Occasional spongiosis and exocytosis of mononuclear cells;

Scale crust formation in association with changes of excoriation (fibrin deposition and cellular debris) ;

Prominent hyperplasia of hair follicles;

Mild fibosis of papillary and superficial dermis and telangiectasia ;

Mild to moderate perivascular mononuclear inflammatory cell infiltrate composed of lymphocytes, histiocytes and plasma cells ;

Nerve hyperplasia as reported in the past is not usually a feature.


Differential diagnosis: Diagnosis is not difficult if the biopsy is big enough.

In small biopsies differential diagnosis include Keratoacanthoma and other causes of pseudo-epitheliomatous hyperplasia.

Note:   Pseudoepitheliomatous (pseudocarcinomatous) hyperplasia :  This is a benign pathological reaction pattern, histologically  characterized by bulbous thickening of  squamous epithelium (follicular infundibula and acrosyringium).

There is abrupt transition  beween lesion and adjacent epidermis. The cells have abundant often glassy cytoplasm.

Pseudoepitheliomatous hyperplasia is seen in the following conditions:

Chronic irritation ;  skin trauma ;  dermal inflammatory processes like  chromomycosis ; aspergillosis ;  pyoderma, Prurigo nodularis ; Granuloma fissuratum and in associatiation with chondrodermatitis nodularis helicis ; Spitz nevus , melanoma, overlying granular cell tumour and cutaneous T cell tumour .



Further reading:

Prurigo nodularis and dialyzer membrane.

Prurigo nodularis: systematic analysis of 58 histological criteria in 136 patients. 

Prurigo nodularis: a review.

Increased nerve growth factor- and tyrosine kinase A-like immunoreactivities in prurigo nodularis skin -- an exploration of the cause of neurohyperplasia.

Eosinophil cationic protein- and eosinophil-derived neurotoxin/eosinophil protein X-immunoreactive eosinophils in prurigo nodularis.

Light and electron microscopic immunohistochemical observations of p75 nerve growth factor receptor-immunoreactive dermal nerves in prurigo nodularis.

Helicobacter pylori and prurigo nodularis.

Granulomatous Reaction Pattern of the Skin

Granuloma Annulare

Necrobiosis Lipoidica

Necrobiotic Xanthogranuloma   

Rheumatoid Nodule

Lupus Vulgaris

Cutaneous Sarcoidosis

Melkersson Rosenthal Syndrome

Annular Elastolytic Giant Cell Granuloma

Skin lesion in Crohn's Disease

Blastomycosis-like pyoderma

Foreign body granuloma


Interstitial   Granulomatous   Dermatitis

Interstitial   Granulomatous Drug Reaction


Benign sweat gland tumours

Hydrocystoma -Eccrine/Apocrine


Eccrine/Apocrine naevus

Eccrine Angiomatous Hamartoma

Porokeratotic eccrine ostial naevus

Syringocystadenoma Papilliferum

Hidradenoma Papilliferum

Nipple Adenoma




Chondroid  Syringoma



Apocrine adenoma

Papillary eccrine adenoma


Malignant sweat  gland tumour 

Microcystic adnexal carcinoma

Eccrine epithelioma

Adenoid cystic carcinoma

Mucinous carcinoma


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