(d) Spinal injury
(a) Sickle cell disease
(a) Basal cell carcinoma
(b) Squamous cell carcinoma
(a) Necrobiosis lipoidica
(b) Fat necrosis
9. Pyoderma gangrenosum
10. Autoimmune ulcers
11. Hypertensive ulcers
Several studies have implicated infectious causes for lower-limb ulceration. However, there is no large cumulative experience, and the literature on infectious ulcers is composed of mostly of small series or case reports. Most infectious ulcers are bacterial although viruses, parasites, and fungi have been reported as causative agents mainly in the immunocompromised patients. A list of likely pathogens is included in Table 16.2.
Infectious causes of limb ulcers
Meningococcus and others
Herpes, CMV, Lues maligna
HSV, CMV, Treponema pallidum
Bacteroides, Borrelia vincenti
Maduramycosis (eumycetoma/mycetoma), Exophiala jeanselmei
Ulcerating cutaneous tuberculosis
Leishmania donovani complex
16.1.1 Mixed Etiology
Most ulcers have more than one etiology. Ulcers of any primary origin such as ischemic, venous, or neurotropic ultimately get infected as well. Though the dominant disease process must be treated first, the superimposed infections require treatment also.
16.1.2 Pyoderma Gangrenosum
This is a misnomer because these ulcers are noninfected and are an important cause of non-healing ulcers of the leg. Ulcers of pyoderma gangrenosum may be associated with inflammatory bowel disease, inflammatory arthropathy, or myeloproliferative disorders . Half of these ulcers are associated with chronic disease and the remainder are idiopathic. Lesions of the lower limb start as painful pustules which progress to necrosis and ulceration. These ulcers may be single or multiple with raised purple serpiginous undermined borders. Besides antibiotics, immunosuppressive therapy forms the mainstay of treatment.
16.1.3 Mycobacteria-Associated Leg Ulcers
Chronic ulceration due to atypical mycobacteria is a rare but important cause of non-healing leg ulcers. The organisms implicated are Mycobacterium ulcerans, Mycobacterium marinum, and Mycobacterium chelonae. The ulcers may start as a subcutaneous nodule and later transform into an undermined ulcer with an areola. The diagnosis is established by polymerase chain reaction-based identification of the organism. Treatment is with oral clarithromycin and topical silver sulfadiazine with hyperthermia . The therapy needs to be continued for several months, and additional antibiotics may be required for secondary bacterial infection.