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Tuberculoid Leprosy
| • | localized, asymmetric, sharply demarcated, centrally hypopigmented, and often anesthetic plaque |
histology:
| • | elongated tuberculoid (but non-caseating) granulomas situated mostly in the lower half of the dermis (bacilli rarely found) |
| • | intraneural granulomatous inflammation = pathognomonic |
pathogenesis:
| • | cell-mediated immunity is strongly expressed |
| • | infection is restricted to one or a few skin sites |
| • | lymphocytic infiltration rapidly causes nerve damage |
| • | Th1 cytokines (IL2, interferon gamma) promote macrophage activation |
Lepromatous Leprosy
| • | diffuse symmetric erythematous plaques; the lesions spare only the warmest areas of the body such as the scalp, axillae, groin, perineum (i.e. intertriginous sparing), and mid-line of the back |
| • | large peripheral sensory nerves are the first affected, giving a “glove and stocking” anesthesia (test dorsal surface of hands and feet, as palms and sole sensation affected only very late in disease) |
histology:
| • | epithelioid granulomata are not a feature, rather there is widespread infiltration by an almost pure infiltrate of macrophages (with a Grenz zone) |
| • | foamy vacuolated macrophages (AKA lepra or Virchow cells) - appearance due to the presence of intracytoplamsic lepra bacilli |
| • | Fite stain is dramatic showing clumps (globi) of bacilli in Lepra cells |
pathogenesis:
| • | display a humorally mediated immune response to infection |
| • | Th2 cytokines (IL4, IL5, IL10) |
| • | CD8 lymphocytes predominate (peripheral CD4/CD8 ratio reverses to 0.6) |
treatment:
| • | paucibacillary disease (i.e. negative skin smear) – dapsone QD and rifampin Q month (6 monthes) |
| • | multibacillary disease (i.e. positive skin smear) – dapsone QD, rifampin Q month, clofazamine Q month X 2 years |
Borderline stages are the most unstable form of leprosy:
Type I (Lepra) reactions:
| • | = the result of changes in cell-mediated immunity... |
| • | can lead to severe swelling of the skin and nerves with increased risk of nerve damage |
| • | therefore treatment of choice = PO steroids |
| • | downgrading = tuberculoid --> lepromatous |
| • | upgrading (AKA reversal reactions) = lepromatous --> tuberculoid ; occur when therapy is begun |
Type II (ENL erythema nodosum leprosum) reactions: (mnemonic – there are more than one type of type II reactions)
| • | = immune complex mediated |
| • | typically in patients with LL or BL (have large antigen load) |
| • | clinical – tender nodules between existing lepromatous lesions; lesions develop in crops and may ulcerate; fever and arthralgias |
| • | histology – LCV; lobular panniculitis |
Lucio’s phenomenon:
| • | seen in Mexican and Central American patients with untreated LL |
| • | diffuse tender ulcerations on the distal extremities and buttocks |
| • | histology: ischemic necrosis secondary to vascular occlusion of medium size vessels |
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