Pathergy in atypical eosinophilic pustular folliculitis
Authors: Hsu Pai‐Jui , Huang Chien‐Jen , Wu Meng‐Tse 
Published: March 2005

A 15‐year‐old, unmarried female presented to our dermatology department for an intensely pruritic skin rash that had appeared abruptly 3 days earlier. She had a remarkable medical history for a case of allergic rhinitis and several attacks of asthma in her early childhood. The condition waxed and waned initially but had improved in recent years. Physical examination revealed several erythematous plaques, papules studded with scattered pustules having diameters less than 0.3 mm. Conspicuous scratch marks had caused erythematous wheal‐like indurations also studded with pustules in a linear distribution across the waist, forearms (Fig. 1), and back (Fig. 2). Discrete papulopustules were present on the face, nape and neck. The patient was otherwise healthy. There were no other symptoms such as fever, malaise, weakness, or lymphadenopathy

Papulopustulosis with adjacent linear Koebner form distribution over the flexor aspect of the forearm

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The pathergy phenomenon observed on the right upper back

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Laboratory results were normal for hepatic and renal functions, serum electrolytes, glucose, protein, erythrocyte sedimentation rate (8 mm/h), and C‐reactive protein (0.355 mg/l). A human immunodeficiency virus (HIV) antibody screen test was negative. Serum was positive for herpes simplex virus (HSV)‐1 and HSV‐2 IgG (in low titers), but negative for HSV‐1 and HSV‐2 IgM. White blood cell count revealed leukocytosis (11.2 × 103/l), with a differential count of 68% neutrophils, 27% lymphocytes, and 8% eosinophils. Serum IgA, IgG, and IgM were within normal limits, but the IgE level was elevated (677 mg/dl). Cultures from peripheral blood and pustules were negative. A Tzank smear performed on the pustules showed no multinucleated giant cells. Fungal testing of skin scrapings from the initial lesion site gave negative results. Routine stool tests, including common pathogen and parasite screens, were negative, and urinalysis results were unremarkable.

A biopsy specimen obtained from a skin pustule showed subcorneal eosinophilic and neutrophilic pustules in the follicular infundibulum with marked spongiosis of the follicular epithelium. (Fig. 3). There was a moderately dense superficial and deep perivascular mixed inflammatory cell infiltrate comprising eosinophils, neutrophils and lymphocytes. Migration of eosinophils and neutrophils through the vessel wall with variable luminal intramural fibrin deposition, histologically indicative of vasculopathy, was seen. There was concomitant slight perivascular dermal necrosis. (Fig. 4)

There is a striking inflammatory reaction involving the follicle characterized by migration of eosinophils, lymphocytes and neutrophils into the outer root sheath epithelium of the follicle (there are perifollicular vasculopathic changes, including those occurring in the context of red cell extravasation)

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The perifollicular microvasculature demonstrates endothelial cell hyperplasia with striking proplastic alterations of the endothelium leading to luminal attenuation (⋆). The perivascular connective tissue exhibits incipient necrobiotic change, fulfilling morphologic criteria warranting the designation of pathergy (→)

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Based on the clinical presentation and light microscopic findings on biopsy, a diagnosis of eosinophilic pustular folliculitis with pathergy was made. Systemic prednisolone 30 mg in divided doses was given. After 1 week of systemic corticosteroid therapy, the patient's condition was significantly improved and the patient was subsequently discharged. Two months later she had a relapse, upon which corticosteroid therapy was commenced leading to lesional resolution. The foci of eosinophilic folliculitis healed with areas of hyperpigmentation with variable scarring.