Pure Bullous Pyoderma Gangrenosum, a Challenging Clinico-Pathological Diagnosis: Critical Literature Review with Emphasis on Diagnostic Criteria

Abstract

Pyoderma gangrenosum (PG) is an uncommon, idiopathic, neutrophilic dermatosis characterised by large necrotic ulcers. Occasionally, patients develop atypical presentations, including pustular, bullous, and vegetative lesions. Bullous pyoderma gangrenosum (BPG) is considered an extremely rare form. We describe a case of BPG in a 76-year-old man, with active oncological history, including a recent diagnosis of hairy cell leukemia. Diagnosis of PG was delayed because of atypical clinical presentation that mimicked necrotising fasciitis. The patient was treated with diverse intravenous antibiotics and several surgical procedures. The suspicion of neutrophilic dermatosis arose from the histopathological studies. In the setting of mandatory clinico-pathological correlation, the aim of this report is to point out the morphological characteristics that allow recognition of this uncommon variant of pyoderma gangrenosum.

Keywords: Bullous; haematologic malignancies; neutrophilic dermatosis; pathergy; pyoderma gangrenosum.

Figure 1

(a) Clinical picture of the initial lesion showing a poorly defined, large, edematous, and equimotic plaque, with haemorrhagic bulla, on the dorsum of the left hand. (b) Haemorrhagic bulla that subsequently presented on the right forearm. (c) Details of haemorrhagic bulla, with bright erythematous halo, that appeared on the trunk

Figure 2

Panoramic histological view of large confluent abscesses filling the dermis and hypodermis under the preserved epidermis (H and E × 20)

Figure 3

Medium power showing details of the large collections of neutrophils and haemorrhagic foci in the dermis (H and E × 100)

Figure 4

Panoramic, histological view of superficial erosion, covered by purulent exudate (H and E × 20)

Figure 5

Histological details of haemorrhagic intra-epidermal vesicles (H and E × 100)