mycobacterial dz Flashcards
leprosy epidemiology/transmission/classification
Overview: caused by m leprae, parasite of macrophages and Schwann cells; peak incidence age 10-15 and 30-60 yo; incubation 4-10 years; transmitted via eroded skin and/or oral/nasal droplets; classified based on cell-mediated immunity —> intact immunity (tuberculoid), poor cell-mediated immunity (lepromatous), dimorphous (can be borderline TL, borderline LL), borderline-borderline, and indeterminate
lepromatous leprosy
TH2 response, multiples organisms can be found in the dermis, a/w HLA-DQ1, sx: diffuse, symmetric, poorly defined, erythematous macules/papules/nodules/plaques on the face, butt, lower extremities +/- leonine facies, madarosis (loss of eyelashes and/or eyebrow) +/- anesthesia/hypesthesia, enlarged and palpable peripheral nerves. Path: virchow cells - multiple bacilli + lipid, + grenz zone, + FITE stain. Dx: bacilloscopy (just make a small incision into one of the lesions, express the contents and place onto a slide, should be able to see organisms)
tuberculoid leprosy
TH1 response, a/w HLA-DR2/3, very few organisms can be found in the dermis. Sx: single or few, asymmetric, well-defined ELEVATED borders of infiltrating, hypopigmented macules and plaques +/- alopecia +/- anesthesia/hypesthesia, enlarged and palpable peripheral nerves. Path: dermal granulomatous infiltrate with a linear pattern as it follows the course of a nerve, epitheloid and langerhan cells are surrounded by lymphs, no organisms, no positive staining. Dx: biopsy best given lack of organisms
what is main complication of leprosy treatment?
type 1/2 reactions, either cell-mediated or immune complex mediated
What do these reactions look like?
type 1 (increase in cell mediated immunity, may occur in any type of leprosy) presents with new skin lesions and increased inflammation of old skin lesions, is a/w neuritis. Tx: prednisone. The other is type 2 (formation of immune complexes, more common in LL) presents as a small vessel vasculitis specifically erythema nodosum leprosum. Tx: thalidomide. Lastly, patients with diffuse LL may develop Lucio phenomenon which is characterized by thrombotic phenomena and necrotizing small vessel vasculitis. Tx: prednisone
cutaneous TB
- M. tuberculosis is the predominant etiologic agent in cutaneous TB. Occasionally, M. bovis and bacille Calmette-Guérin (BCG), an attenuated strain of M. bovis, may produce skin lesions
- disseminates primarily via inhalation of aerosolized droplets of saliva from individuals with active disease; transmission by ingestion or inoculation can also occur
- pathophys: largely mediated by granuloma formation
- clinical manifestations depend on TB exposure type: EXOGENOUS, ENDOGENOUS, or inoculation (TUBERCULIDS). If exogenous, then will present with TB chancre or TB verrucosa cutis. If endogenous, then will present with scrofuloderma, miliary TB, TB gumma, orificial TB, or lupus vulgaris. If inoculation, then will present with papulonecrotic eruption, lichen scrofulosorum, and erythema induratum (basically EN of the calves rather than shins)
- The tuberculids represent a group of disorders that classically were associated with a focus of internal TB. They are considered immune reactions within the skin due to hematogenous dissemination of M. tuberculosis or its antigens from a primary source, in an individual with strong antituberculous cell-mediated immunity.
mycobacterium ulcerans
Aka buruli ulcer, #3 most common in immunocompetent host after tuberculosis and leprosy. May be caused by water resorvoir (river/ponds). Sx: ulcer(s). Dx: PCR. Tx: surgery for small lesions, otherwise hyperbaric oxygen and wound care
mycobacterium marinum
Caused by bacterium in aquatic environment (even swimming pools and fish tanks). Sx varies, plaque/sporotrichoid pattern/disseminated pattern in immunocompromised. Dx: culture. Tx: clariththromycin (+ rifampin or ethambutol, if severe infx)
mycobacterium kansassi
Closely related to m. Tuberculosis thus an infection with this organism can give you protective immunity against TB. May be caused by water resorvoir. Path: may be similar to TB. Sx: variable. Dx: PCR. Tx: Isoniazid (or clarithromycin) + rifampin + ethambutol ± pyridoxine; other options (depending on susceptibilities) include azithromycin, moxifloxacin, streptomycin and sulfamethoxazole
Mycobacterium fortuitum, Mycobacterium chelonae, Mycobacterium abscessus
These are all saprophytes meaning microorganisms that live off of dead/decaying organisms. Infections typically occur following trauma, surgery or other procedures, including contact with contaminated medical instruments (e.g. liposuction, mesotherapy), placement of implants (e.g. prosthetic breast implants) and tattooing
Sx: multiple erythematous subcutaneous nodules, frequently occurring on the distal limbs or in a sporotrichoid pattern. Dx: culture or PCR. Tx: surgical exicision + clarithromycin (for the latter) and ciprofloxacin (for the former, m. Fortuitum)
MAC Mycobacterium avium complex
The organism is found in the environment, including fresh and salt water, soil, dairy products and domestic animals. It may be transmitted via inhalation into the lungs, or via water and food into the GI tract. A/w AIDS patients. Skin involvement is unusual and most often presents with papulopustules and multiple purulent leg ulcers. Nodules with abscess formation, panniculitis, sinus tracts, folliculitis and granulomatous plaques may also be seen. A papulonecrotic tuberculid-like eruption due to disseminated MAC has been reported in patients with AIDS. Dx: culture from skin bx or PCR. Tx: Clarithromycin or azithromycin + ethambutol ± rifampin or rifabutin
Mycobacterium haemophilum
Often seen in immunosuppressed patients. Sx (immunosuppressed) single bluish-red tender pustule, papulonodule or plaque, which evolves into an abscess and/or ulcer. Sx (immunocompetent) isolated lymphadenitis (often seen in children). Dx: Tx: Surgical excision + Clarithromycin + rifampin ± ciprofloxacin or amikacin
*relies on ferric ions to grow thus it is called m. haemophilum
Mycobacterium scrofulaceum
affects children and seems to occur via inhalation or ingestion. Sx: lymphadenitis and skin lesions in a sporotrichoid pattern. May be clinically indistinguishable from scrofuloderma. Dx: culture. Tx: total excision of involved lymph nodes + Isoniazid + rifampin**, clarithromycin. Ideally surgery is the best treatment, but the 2 antibx listed have been shown to be helpful in addition to surgical interventions.
