Bacteria 5 (mycobacterium): Leprosy Flashcards
Which organism causes leprosy?
Mycobacterium leprae
- Intracellular parasite, therefore unable to culture in vitro
- Host: man, armadillo, monkey
- MD-Anti-leprosy tx 95% effective, little drug resistance, nerve damage often amenable to steroid treatment
- Also called Hansen’s disease
How does leprosy spread and where is it most commonly found?
- Low infectivity: person to person droplet inhalation via URT
- incubation period up to 7 years
- peak incident age: 20 - 30 years
- Incubation typically years but can be up to a decade
- Host immunity and dose of AFB determines manifestation of disease
- About 95% will develop no clinical evidence of disease
- India/Bangladesh (70%), Brazil, Tanzania/Angola, China
- HIV infection not a risk factor disease acquisition
How is leprosy diagnosed and what are the diagnostic criteria for leprosy?
- Essentially clinical dx
- Clinical signs + acid-fast bacilli on slit skin smear
- Skin lesions: test small muscles and sensation of hands and feet (ideally using monofilament)
- Slit skin smear: incision through epidermis, scrape dermal material and smear onto glass slide -> stained -> count number of bacilli per field
What other symptoms can we find in leprosy patients?
What is the pathophysiology of leprosy?
Chronic, granulomatous condition, where bacteria infect macrophages and the peripheral nervous system (Schwann cells). Immunology is complicated and determines the spectrum of clinical picture
- LL [lepromatous] form of the disease the cellular immunity [CMI] is poor and there is an antibody-mediated response. It becomes a generalised condition and bacteria are found throughout the body/tissues.
- TT [tuberculoid] form of disease has high CMI response and less bacteria and fewer clinical features.
- The borderline conditions lie in-between on the spectrum and are unstable.
- Type of leprosy can change with changes in immunity over lifetime
What is the Ridley-Jopling classification of leprosy?
How does the WHO classify leprosy for field purposes?
WHO simple classification for field based:
- Paucibacillary 5 lesions or less (TT, BT) – “Tuberculoid” – note you will not find bacilli on a skin smear
- Multibacillary >5 lesions (BB, BL, LL) – “Lepromatous”
What is the morphological appearance of skin lesions in different types of leprosy?
Clinical Features of L v T
- Lepromatous LL includes nodular • Diffuse lepromatous disease has the lionian appearance
- Borderline can be mixed within the same patient: some areas more BT/BL
- Indeterminate leprosy: Hypopigmented lesions with wide differential and biopsy only show mild inflammatory changes.
How do you manage leprosy?
Rifampicin (600 mg once a month), Dapsone (100 mg daily), Clofazimine (300 mg once a month and 50 mg daily) for 12 months
Rifampicin -> RNA synthesis inhibitor
Dapsone (DDS) -> blocks folic acid synthesis, can causes DDS syndrome, which is an exfoliative dermatitis with LNadenopathy, HSM and fever
Clofazimine -> it’s a dye, which can discolour the skin from red to purple, the discolouration usually fades after 6 - 12 months
Patients that develop tender nerves -> start prednisolone therapy
Non-pharmacological measures:
- Education about how to prevent neuropathic complications
- Eye care
- Foot care
- Social and psychological support
- Careful monitoring of sensation
- Surgery to correct deformities/remove infected tissues
What different types of leprosy reactions are there and how are they precipitated?
What is the WHO Global Leprosy Strategy?
MCQ Key words
A diagnostic scenario is likely to be complications of either dermatological or neurological sequelae of leprosy
- Know the treatment schedules for different types of leprosy and it might be helpful to know the main side effects of these drugs too.
- Histology picture may show acid fast bacilli on slit skin smear -> REMEMBER: THESE WILL NOT BE FOUND ON PAUCIBACILLARY Leprosy
- Distinguish Type I and Type II reactions and how to manage them
- Recognise photographs of the nodular and lionian appearance of leprosy and Erythema Nodosum Leprosum
