This condition presents suddenly in the form of a small, reddened, painful pustule, most commonly due to any trauma affecting the skin. This pustule may then grow bigger in size and eventually burst, leaving behind an ulcer. The ulcer usually keeps enlarging and there may be more than one such ulcers. They also rapidly deepen and are extremely painful.

The ulcer(s) may keep on enlarging or start healing on their own, depending upon the host's immune system.

Culture negative pulmonary infiltrates are the most common extracutaneous presentation [7].

Work up includes a detailed history and physical examination followed by tests.

Laboratory Tests

• Complete blood count
• Blood profile
• Liver function tests
• Urinalysis 
• Kidney function tests
• Tissue culture of affected area
• VDRL Test to exclude STDs
• Antiphospholipid antibody test to exclude Wegener's and vasculitis
• Serum immunofixation electrophoresis to rule out gammopathy

Imaging Studies

Imaging studies are not usually done, however, a chest and abdominal X-ray and/or CT scan, bone marrow biopsy, colonoscopy and other such tests may be performed to check for underlying systemic diseases, if any.

Test Results

The diagnosis of pyoderma gangrenosum does not have any definite diagnostic factors or tests. So the diagnosis is made based on exclusion of all other diseases.

Medications

Antibiotics are generally not helpful for treating uncomplicated cases of pyoderma gangrenosum [8]. The drugs that may be given for treatment of pyoderma gangrenosum are:

• Immunomodulators like Infliximab, Thalidomide, Clofazimine, etc.
• Immunoglobulins
• Immunosuppressants like Cyclosporine, Azathioprine, Chlorambucil, etc
• Corticosteriods
• Topical therapies like Cromolyn sodium, Aminosalicylic acid, etc.

The best documented treatments for PG are systemic corticosteroids and Cyclosporin A [9].

Surgical Treatment

Surgery should be avoided, if possible, because of the pathergic phenomenon that may occur with surgical manipulation or grafting, resulting in wound enlargement [10].

Some reports suggest that about half of pyoderma gangrenosum patients have recurrences [5]. However, it should be noted that unless there are complications, the prognosis of this condition is generally very good.

Once the appropriate treatment is begun, the most effective being a combination of immunosuppressant and corticosteroid, the ulcer heals with minimal scarring. Follow up is generally required but not extensive, providing the ulcer isn't very deep and the condition is uncomplicated.

Complications

Ulcerations of pyoderma gangrenosum occur after trauma or injury to the skin in about 30% of patients; this process is termed pathergy [6].

Common complications include:

• Deeply penetrating ulcer
• Numerous ulcers
• Ulcer becoming infected
• Ulcer damaging the vasculature leading to haemorrhage 
• Scarring
• Death (extremely rare)

Pyoderma gangrenosum is an idiopathic condition which may or may not occur due to an underlying systemic disease. It is however proven that the disease is brought upon by an abnormal immune response, more precisely, excessive activity of neutrophils, that results in inflammation of an area of the skin, pustule or nodule formation and the end stage is usually an enlarged ulcer.

Other than inflammatory bowel disease (IBD), arthritis, systemic lupus erythematosus (SLE) and gammopathies, diseases like myeloid dyscrasias, Wegener granulomatosis, chronic hepatitis, PAPA syndrome, etc may also lead to this condition.

Incidence

Each year in the United States, pyoderma gangrenosum occurs in about 1 person per 100,000 people [3].

Age

It mostly affects people in their 40s or 50s [3].

Sex

Pyoderma gangrenosum is more common in females.

This disease occurs due to overexpression of Interleukin 8 (IL-8) in the area of the skin lesion. IL-8 is a potent chemotactic factor of neutrophils. As a result, abnormally large numbers of neutrophils aggregate in the affected area causing the lesion to worsen and ultimately, an ulcer is formed. Depending upon how long the abnormal inflammatory process goes on, the ulcer may get enlarged or start healing on its own.

Pyoderma gangrenosum is of two main types:

• Typical Pyoderma gangrenosum which occurs in the skin of the lower limbs.
• Atypical pyoderma gangrenosum which may occur anywhere else on the body, most commonly affected region being the upper limbs (superficial skin of the hands).

Other less common types include:

• Pustular Pyoderma gangrenosum [4]
• Vegetative Pyoderma gangrenosum
• Peristomal Pyoderma gangrenosum
• Bullous Pyoderma gangrenosum

Pyoderma gangrenosum is a disease occurring due to abnormal immune response. So it does not have an exact prevention. However, by treating any systemic disease appropriately may decrease the risk of developing this condition. Also, by treating any skin lesion promptly may prevent its progression to this disease.

Pyoderma gangrenosum (PG) is an uncommon, ulcerative, cutaneous condition with distinctive clinical characteristics first described in 1930 [1]. It is a disease in which a painful pustule may form, increase in size and break down, forming an ulcer.

Pyoderma gangrenosum is an idiopathic condition. Lesions may occur either in the absence of any apparent underlying disorder or in association with other disease, such as ulcerative colitis, Crohn's disease, polyarthritis, gammopathy and other conditions [2].

This condition is due to an abnormal immune process in response to any trauma affecting the skin. It may begin as a small, red painful swelling, nodule or pustule and lead to ulcer formation and scarring. If you develop such a condition and if you already suffer from a systemic disease like any mentioned above, you should contact your physician immediately.

1. Champion RH, et al., eds. Textbook of Dermatology. 5th ed. Cambridge, MA: Blackwell Scientific Publications; 1992:1922-26.
2. Freedberg IM, Eisen AZ, Wolff k. Fitzpatrick Dermatology in General medicine, 6th ed. New York: McGraw Hill;2003
3.  Jackson, J Mark, Callen, Jeffrey P (Apr 23,2012) "Pyoderma Gangrenosum" In Elston. Dirk M. Emedicine
4. Shankar S, Sterling JC, Rytina E. Pustular pyoderma gangrenosum. Clinical and Experimental dermatology 2003 28(6); 600-3 
5. Von Den Driesch P: pyoderma gangrenosum: a report of 44 cases with follow up. Br J Dermatol. 1997,Dec;137(6);1000-5 
6. August PJ, Wells GC. Pyoderma gangrenosum treated with azathioprine and prednisolone. 
7. Brown TS, Marshall GS, Callen JP. Cavitating pulmonary infiltrate in an adolescent with pyoderma gangrenosum:a rarely recognised extracutaneous manifestation of a neutrophilic dermatosis. J Am Acad Dematol. Jul 2000 43(1 pt 1):108-2
8. Lyon CC, et al. Parastomal pyoderma gangrenosum: clinical features and management. J Am Acad Dermatol. 2000;42:992-1002
9. Armstrong PM, et al. Pyoderma gangrenosum. A diagnosis not to be missed. J Bone Joint Surg Br. 1999;81:893-94.
10. Baranska-Rybak W, Kakol M, Naesstrom M, Komorowska O, Sokolowska-Wojdylo M, Roszkiewicz J. A retrospective study of 12 cases of pyoderma gangrenosum: why we should avoid surgical intervention and what therapy to apply. Am surg. Dec 2011, 277(12):1644-9