Pyoderma Gangrenosum of the Scalp: A Rare Clinical Variant

Pyoderma gangrenosum (PG) is a rare, neutrophil-predominant dermatosis that usually presents as a papule or pustule and progresses into a painful ulcer. Clinical and histopathological features are nonspecific, making PG a challenging condition to diagnose. Lesions may occur anywhere on the body; however, the lower extremity is the most common location.Solitary lesions in atypical locations such as the scalp are uncommon, making this clinical variant especially difficult to recognize and diagnose. Although the clinical features and subsequent management of scalp PG might be different from other anatomic sites, the typical presentation and treatment of scalp PG is still unclear. The authors present a recent case of a 34-year-old woman with scalp PG and summarize 16 other cases documented in the literature. This case report and literature review illustrate several similarities and differences between scalp PG and classic PG: (1) scalp PG occurs in a wider age demographic of patients; (2) as with classic PG, inflammatory bowel disease and pregnancy are associated conditions, but head injury and preexisting inflammatory skin conditions of the scalp may be additional predisposing factors for scalp PG; and (3) as with classic PG, scalp PG generally responds well to corticosteroids and immunosuppressive therapy. Scarring occurs in all conditions, though disfigurement and psychosomatic effects may be disproportionately higher in scalp PG.

Pyoderma gangrenosum (PG) is a rare, noninfectious, neutrophilic dermatosis with an incidence between 3 and 10 patients per million.¹ The associated lesions typically begin as pustules or papules that undergo central necrosis and extend peripherally to produce ulcers.² While PG lesions may be found on any anatomic site, lesions on the lower extremity are by far the most common.³ Cases of scalp PG only constitute a small subset of patients, making this clinical variant especially difficult to recognize and diagnose. 

The scalp is a unique skin area with a high follicular density, elevated rate of sebum production, and high blood supply.^4,5 Hypothetically, this rich vascularization averts dermatologic disorders that may otherwise cause ulceration.⁶ However, when scalp ulceration is present, its impact is important since patients may experience significant psychosocial discomfort. Presentation and management of scalp PG could be different than PG on other anatomic sites, but the clinical presentation, histological features, and most appropriate treatment of this clinical variant is still unclear. The authors report 1 case and review 16 other documented cases^7-20 of scalp PG. 

A 34-year-old woman with history of ulcerative colitis was transferred to Virginia Commonwealth University, School of Medicine (Richmond, VA) with the diagnosis of worsening culture-negative necrotizing fasciitis of the scalp and neck, which had started as an abscess behind the right ear (Figure 1A). Despite multiple debridements in a community hospital (number of debridements unknown), the ulceration had not improved. The patient was having an ulcerative colitis flare 1 to 2 months prior to her initial presentation with the ulcer, which was being treated with prednisone. Upon arrival (Figure 1A), the patient was already intubated and had extensive ulceration of the right scalp exposing the muscles and calvarium. The patient was managed by a multidisciplinary team consisting of plastic surgery, infectious disease, and dermatology. 

Biopsy revealed ulceration with acute and chronic dermal inflammation. Tissue cultures were positive for Candida albicans. The multidisciplinary team initially recommended against immunosuppression and an infectious etiology was favored, supporting treatment with intravenous (IV) antibiotics. On hospital day 18, she was taken to the operating room to improve wound care and reposition her right ear. She had no new lesions afterwards. Three weeks later (day 40), she was taken back to the operating room for local debridement and advancement of local tissue of the head and neck with the use of a synthetic dermal substitute (Integra; Integra LifeSciences, Plainsboro, NJ). Unfortunately, 2 days postoperatively, she developed necrosis of the local flaps followed by loss of the synthetic dermal substitute and a Serratia marcescens superinfection, requiring removal of the flap. On day 43, she was then scheduled for free muscle flap coverage and skin grafting while on broad-spectrum antibiotics. She underwent coverage of the calvarium using a latissimus muscle flap; the muscle flap was covered with a split-thickness skin graft (STSG) from her thigh. She had an uneventful postoperative course and was noted to have complete graft take and no donor site complications. 

Ten weeks later, the patient returned to the hospital through the emergency room with an acute increase in scalp pain in addition to significant STSG loss (Figure 1B). A superficial bacterial culture of the affected area revealed methicillin-sensitive Staphylococcus aureus, but tissue cultures were unrevealing. She was treated with broad-spectrum IV antibiotics. One week after her readmission, she developed new superficial ulcerations on areas of previously healthy scalp tissue. At this point, the presumptive diagnosis of PG was made, and her treatment regimen shifted focus. She was initially treated with high-potency topical corticosteroids and antibiotics before being switched to high-potency topical corticosteroids and a calcineurin inhibitor (tacrolimus 0.1% ointment). She showed significant improvement within a day and was discharged home. 

About 6 months later, the patient was hospitalized with a second PG flare up (Figure 1C). She was initially treated with IV antibiotics and then was changed to a systemic steroid-based immunosuppressive regimen (prednisone 60 mg) supplemented with high-potency topical corticosteroids alternated with mupirocin. The patient was started on a prednisone taper; the dose was decreased by 10 mg every 2 weeks. Six weeks later while tapering (20 mg), she developed superficial ulcerations on the scalp and a new ulcer on her left upper back. Her prednisone dose was increased and mycophenolate mofetil (1500 mg twice per day) and dapsone (100 mg daily) were added to her regimen. The patient currently remains stable on 5 mg of prednisone, 2 g of mycophenolate mofetil, and 100 mg of dapsone (Figure 1D).

In a review of the literature conducted in PubMed, the authors identified 16 other cases^7-20 that described PG lesions of the scalp. 

Classic PG is most common in adults aged 20 to 50 years²¹; however, PG of the scalp frequently occurs in the pediatric and geriatric patient populations. Out of the 16 total cases of scalp PG (plus the present case making this 17), 24% were under the age of 21, 35% were between 22 to 50 years old, and 41% were over the age of 50. Also, data suggest PG affects women slightly more often than men.³ In the reviewed cases,^7-20 65% were female and 35% were male, keeping with this expectation.

In many cases, PG is associated with an underlying comorbidity such as inflammatory bowel disease (IBD), hematologic disorders (myelodysplastic syndrome, multiple myeloma), or inflammatory arthritis.²² Of the 17 patients, 5 (29%) had a PG-associated comorbidity; in each case, the association was IBD.^11,13,16 In one case,¹³ IBD was diagnosed after diagnosis of PG, whereas the remainder^11,16 (and present case) had a prior history of IBD. Another patient was subsequently diagnosed with ulcerative colitis when presenting with PG on the leg 5 years after successful treatment of scalp PG.¹³ 

Preexisting inflammatory skin disease may predispose the development of PG of the head and neck.¹¹ One of the reported patients had a history of chronic ulcerative dermatosis of the scalp and tinea capitis.²⁰ Another had concurrent psoriasis, though the psoriatic lesions were not on the scalp.¹¹ The present patient had been diagnosed with tinea capitis by culture 3 months prior to the onset of PG.

Pyoderma gangrenosum classically follows minor trauma of the skin, a concept known as pathergy.²³ Two cases^7,19 followed head injury attributed to falls, which are excellent examples of pathergy. 

Histopathologic features of PG are nonspecific (Figure 2) but can aid the diagnosis by excluding other potential diagnoses such as a primary vasculitis, infections, and malignancies.²⁴ Characteristically, PG lesions have a dense neutrophilic infiltrate, but leukocytoclastic vasculitis, necrosis, and even granulomatous inflammation also have been described.^25-27 The histopathology of scalp PG appears to be similar to classic PG. Of the 17 cases reviewed, biopsies were performed on 15 of them.^7-12,14,16 Neutrophil infiltration/acute inflammatory infiltrate was described in 12 cases,^{7,9,11,12,14,17-20} granulation tissue was reported in 5 cases,^{9,10,17,18,20} 1 had necrosis,¹⁰ and 1 had vasculitis present.⁷ 

There currently is no gold standard treatment for managing PG. An immunosuppressive regimen using corticosteroids is considered the mainstay of treatment for most cases.^28,29 Only 16 provided information regarding management; 1 patient had died of lung embolism before initiation of treatment.¹⁹ Of the reported cases, 12 were successfully treated with a regimen that included systemic corticosteroids.^{7,8,11,12,14,15,17-20} Seven cases resolved with systemic steroids as monotherapy.^{7,8,11,12,14,17,18} Data support the use of high-potency topical steroids (clobetasol, halobetasol) in the treatment of PG as well,^30,31 which may be more favorable due to the paucity of adverse side effects³²; however, a topical steroid regimen was used in only 2 patients as adjuvant therapy¹⁶ (including the present case as reference). 

Historically, other systemic immunomodulators (ie, methotrexate, azathioprine, cyclosporine, mycophenolate mofetil, thalidomide, IV immunoglobulin) have been effective in treating PG.^32-37 Six of the cases discussed herein reported success with using an immunomodulator^{9,10,15,19,20}; 4 of the 6 patients were concurrently receiving corticosteroids.^15,19 Miscellaneous medications such as dapsone or anti-inflammatory antibiotics, including minocycline, also have been reported³⁸ to be beneficial for PG. Minocycline was used successfully in 1 case.¹³ Of the 17 cases under discussion, 1 lesion did not heal after dapsone,⁹ yet it is not clear if it did not improve. However, dapsone was a useful steroid-sparing agent in the present patient. Interventional options for scalp PG, organized by priority, are summarized in Table 1. 

Successful surgical management of PG, including skin grafting, has been reported in a few isolated cases after PG has been medically controlled^38,39; however, surgery is usually avoided to prevent pathergy. For the present case, an initial surgical approach was unsuccessful. 

With regard to prognosis, most of the reviewed patients were treated successfully and healed completely. One patient was lost to follow up,¹⁸ and another died of unrelated causes before treatment.¹⁹ None of the cases reported recurrence of scalp PG, but there was recurrence of leg PG in 1 patient 5 years after treatment of the scalp lesions.¹³ Several patients were left with significant scarring.^15,17 Scarring and disfigurement is common in PG patients²⁴; the PG patient described herein also was left with tremendous scarring (Figure 1).

A comparison of classic PG versus scalp PG is summarized in Table 2.

Scalp PG is a unique variant of PG, making up only a small percentage of total cases. It occurs in a wider demographic of patients, as lesions commonly occur in both the pediatric and geriatric populations. Scalp PG appears to be associated with comorbidities and may be disproportionally associated with IBD, although patient age and the small sample size may bias this conclusion. Pathergy after head injury and preexisting inflammatory skin conditions similarly predispose the development of scalp PG. Clinical presentation and histopathological features also appear to be similar to classic PG. Patients often require a rapidly acting, multimodal treatment approach that is corticosteroid based. Overall, after appropriate treatment, scalp PG typically heals; however, scarring and disfigurement are common. 

Affiliations: Virginia Commonwealth University, School of Medicine, Richmond, VA; Virginia Commonwealth University, Department of Dermatology; Virginia Commonwealth University, Division of Plastic and Reconstructive Surgery; and Oregon Health & Sciences University, Department of Dermatology, Portland, OR

Correspondence: Alex G. Ortega-Loayza, MD, Assistant Professor, Department of Dermatology, Oregon Health & Sciences University, 3303 SW Bond Avenue, CHD 16D, Portland, OR 97239; ortegalo@ohsu.edu

Disclosure: The authors disclose no financial or other conflicts of interest.