GIDEON MWASAKYALO

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INTRODUCTIONPyoderma gangrenosum (PG) is a rare, primary sterile, inflammatory, non-infective, and non-malignancy skin disease that is classified into four variants (ulcerative, pustular, bullous, and vegetative) (Table 1). Up to 50% of PG cases might have systemic diseases such as hematological malignancy, rheumatoid arthritis, paraproteinemia, myeloproliferative disorder, and inflamatory bowel diseases such as Crohn’s disease and ulcerative colitis. It’s found that up to 5% of cases of PG have ulcerative colitis and 1.5% have Crohn’s disease (1), (2), (3), (4), (5). In the 1930s, Brunsting et al. were the first to define PG as a disease entity. They described it in five patients who presented with large, painful necrotic ulcers with undermined borders of bluish coloration enclosed by regions of erythema. In those five patients, four had ulcerative colitis. The cause is still unknown, though it was hypothetically thought to be a bacterial disease and sometimes a cutaneous manifestation of inflammatory bowel disease, which has been refuted by current studies (2).The incidence of PG annually in the United States is estimated to be 1 case in 100,000, while the worldwide incidence is between 3 and 10 million. General PG is a diagnosis of exclusion, with penile conditions having considerable differentials, including infections such as syphilis, amoebiasis, herpes simplex, mycobacterial ulceration, and non-infectious origins of venereal ulceration like cutaneous Crohn’s disease, squamous cell carcinoma, and ulcerating sarcoidosis. It should be considered in lesions where antimicrobial or antiviral therapy has not responded or for the non-confirmatory diagnosis of skin conditions (6). Frequently, PG occurs between the ages of 25 and 54, though it might occur at any age. It is extremely rare in pediatrics; 4% of cases have been reported in pediatrics and infants; in infants alone, 8.8% of all pediatric cases are reported. The youngest reported case is 3 weeks old. Females are more affected than males, and their peak age is in their third and fourth decades, while their counterpart males are in their fifth decade. The initial lesion is a tender pustule, whereas in infants, the areas involved are perianal and genital, and in children, the lesions involve the head, face, and gluteal areas (4).Typically, PG lesions start as small vesiculopustular, which progresses to an ulcer with violaceous overhanging borders, and these occur mostly in the lower extremities, though not limited to other organs. In this typical form, it is believed that if the condition is associated with arthritis, they become more refractory to treatment than those without arthritis. Atypical forms are clinically presented as superficial lesions with blue-gray bullous borders involving the extremities, head, and neck. Regardless of the presence of other systemic conditions, it can be acute or chronic. A PG patient presents with a condition called pathergy, which is the development of a lesion at a site of trauma, whether it be iatrogenic, animal bites, or any injury, and it is due to hyper-reactivity of the skin (8). Apart from PG, other conditions that may present with pathology are sweet syndrome, blindloop syndrome, erythema elevatum diutinum, and Behcet’s disease. Pathergy should not be confused with the Koebner/isomormorphic response, which is the formation of new skin lesions in areas that were not involved in trauma. 10–30% of PG reported cases are idiopathic; 20% of patients will present with a Koebner response, while 20–30% will present with pathology (9, 10).