Cause:Mycobacterium leprae
Pathophys:
Both types infect colder tissues, hence hands, feet, ears, nose, peripheral nerves
Unknown mode of transmission, seems to require prolonged (>1 mo) exposure, probably skin and nasal discharge. 3- to 5-yr incubation. Tuberculoid type is not infectious (Ann IM 1978;88:538)
15 million in world; esp children and young adults.
Endemic in SE US armadillos and they are the source of many US cases, how unknown (Nejm 2011;364:1626)
Sx: Years incubation period; eczematous rash; numbness (85%)
Si:
Lepromatous to tuberculoid spectrum: nodular accumulations in skin, mucous membranes, and other organs, esp on face; organisms are in these "globi"; to thickened peripheral nerves; to decreased sensation in extremities leading to mutilation and loss, pain and temperature sensation diminished
Arthritis, septic with bacteria in joint histiocytes (Nejm 1973;289:1410); secondary amyloid; ERYTHEMA NODOSUM LEPROSUMw painful skin nodules, fever, wasting, rx'd w thalidomide (Med Let 1996;38:15)
Lab:
Bact:AFB-positive smears of globi as well as blood and buffy coat since bacteria both free and in wbc's in lepromatous type, decrease in numbers correlates with rx over months, average rx duration = 105 mo (Nejm 1972;287:159); and of marrow histiocytes (Nejm 1979;300:834)
Path:Skin bx of globi and/or nerve bx show epithelioid cell collections without distinct tubercles; nerves surrounded by microscopic tubercles
Serol:VDRL, cryoglobulin, rheumatoid factor often pos in lepromatous, not tuberculoid types
Rx:
Preventive: isolation unnecessary; DDS (Dapsone) effective prophylaxis for household contacts (Ann IM 1978;88:539)
of disease, triple rx w clofazimine 50-100 mg po qd, + sulfones, eg, DDS (Dapsone = diaminodiphenylsulfone), + rifampin; or combinations of minocycline, clarithromycin, ciprofloxacin, and augmentin. Cmplc of rx: erythema nodosum leprosum, rx w thalidomide (Med Let 1998;40:104)
May become noninfectious in weeks to 3 mo; 2+-yr course, longer with lepromatous type