Leprosy!

Today, we talked about the case of a middle-aged man from the Philippines who presented with a one year progressive pruritic rash involving the face, arms, and legs as well as a distal symmetric peripheral neuropathy, found to have lepromatous leprosy on skin biopsy!


Clinical Pearls 

  • Mycobacterium leprae and lepromatosis like to grow in cooler areas, so infection often manifests in the skin and the peripheral nerves.
  • Transmission is likely via respiratory route, through broken skin, and by touching armadillos!
  • Early recognition and treatment is important to prevent injury to peripheral nerves.

DDx for rash + neuropathy

  • Lyme (usually cranial nerves, radiculopathy)
  • Celiac
  • Zoster (tends to be painful rather than pruritic and localized to a dermatome)
  • WNV (flaccid paralysis)
  • Sarcoid
  • Amyloid
  • Syphilis
  • Leprosy

Our patient presented with a pruritic rash and largely a distal symmetric peripheral neuropathy.  We generated the following Venn diagram in report to help us with the diagnosis:

Venn diagram

Leprosy

  • AKA Hansen’s disease
  • Infection caused by mycobacterium leprae and mycobacterium lepromatosis, separate species that cause similar clinical disease. They are both obligate intracellular parasites.
  • Involves the skin and peripheral nerves
  • Early treatment is important to prevent involvement of the eyes, hands, and feet due to neuropathy. The neuropathy is often non-reversible.
  • 205 new cases detected in the US in 2010. 75% among immigrants (most commonly India, Brazil, Indonesia, Bangladesh, and Nigeria)

Transmission

  • Unknown but probably respiratory route especially in lepromatous leprosy. Sometimes can transmit through broken skin. Also from armadillos.
  • Most people do NOT develop disease after exposure. Risk factor for disease development include older age, genetic influences, and immunosuppression.
  • Grows in cooler areas

Clinical presentation:

  • Described in categories pertaining to how much bacillary burden of disease is present with tuberculoid being the least amount and lepromatous having the highest disease burden.
  • Clinical features:
    • Hypopigmented or reddish patches on the skin
      • Typically involve the earlobes with nodular thickening and distributed symmetrically on the body in lepromatous leprosy.
    • Diminished sensation or loss of sensation within skin patches
    • Paresthesias of hands/feet
      • Neuropathy occurs early in disease course
    • Painless wounds or burns on the hands or feet
    • Lumps or swelling on the earlobes or face
    • Tender, enlarged peripheral nerves
  • Late findings in disease course:
    • Weakness of the hands with claw fingers, foot drop, facial paralysis, lagophthalmos (can’t close eyes completely due to CN7 palsy), lack of eyebrows/eyelashes, collapsed nose, perforated nasal septum.
    • Intermittent bacteremia can lead to focal lesions in various organs (liver, bone marrow, testicles and larynx)

Diagnosis:

  • Consider it in patients with skin lesions and/or enlarged nerve(s) accompanied by sensory loss.
  • No reliable blood or skin tests available.
  • Usually clinical and skin biopsy

Treatment:

  • Goal: Prevent and/or minimize injury to peripheral nerves!
  • Often times it’s loss of sensation but later can progress to painful neuropathy
  • Dapsone plus rifampin for tuberculoid leprosy. Clofazimine is added for lepromatous leprosy.
  • Duration can be up to 24 months
  • Treat neuritis with steroids for a prolonged course
  • Make sure to screen for G6PD deficiency before prescribing dapsone
  • Monitor liver function with rifampin
  • Clofazimine (causes phototoxicity) is not available in US pharmacies and must be obtained from the NHDP.

Prognosis:

  • May take a few years for skin lesions to resolve completely with treatment
  • Very curable, low relapse rates, typically no drug resistance
Leprosy epidemiology.png
Distribution of leprosy around the world (source Wikipedia)

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