Overview
- Definition
A chronic granulomatous bacterial infection caused by Mycobacterium leprae, mainly affecting the skin, peripheral nerves, nasal mucosa, and eye
Also known as Hansen’s disease
Infection develops very slowly (can take up to 20 years), and possibly spreads through respiratory droplets, but only after prolonged exposure to untreated individuals; it does not transmit vertically from mother to fetus
- The three major causes of visual disability are as follows
Exposure or neurotrophic keratopathy
Chronic iridocyclitis with hypotony
Cataract formation
- Symptoms
Pain
Redness
Photophobia
- Laterality
Bilateral
- Course
Leprosy is highly curable once diagnosis is made and proper therapy is commenced
Lepromatous uveitis is typically chronic, with little symptomatology
Profound hypotony and phthisis bulbi may ensure if systemic disease and ocular inflammation are not addressed
- Age of onset
Two peaks: 10–14 years and 35–44 years
- Gender/race
Slight male predominance
Very rare in the United States; armadillos are naturally infected in Southern United States
Between 200,000 and 250,000 new cases per year worldwide
- Systemic association
- Skin
Hypopigmented or reddish skin lesions that are numb to heat and touch, thus at risk of cuts and ulcers
Painless swelling or nodules on the face or earlobes
- Peripheral nerves
- Enlarged peripheral nerves that are hard and tender to touch
Predilection for ulnar, posterior tibial, and external popliteal nerves
Untreated, advanced leprosy results in paralysis of hand and feet
- Nasal mucosa
Epistaxis
Saddle-nose deformity
Exam: Ocular
External
Loss of brow hair or lashes
Lagophthalmos (facial nerve paralysis)
Anterior Segment
- Exposure or neurotrophic keratopathy
Focal enlarged corneal nerves, resembling beads on a string (pathognomonic)
- Iridocyclitis is more often chronic than acute
IOP is often low
- “Iris pearls.”
Pathognomonic
Arise deep in the stroma of the iris and are opaque, dense, creamy yellow, and firm (in contrast to Koeppe nodules, which are grayish, semi-translucent, and soft in appearance)
Diffuse episcleritis/scleritis
Posterior Segment
“Pearls” in anterior choroid
Nonspecific hyperpigmentation or hypopigmentation of the RPE
Focal or disseminated choroiditis (rare)
Exam: Systemic
Hypopigmented or reddish skin lesions with thickening and numbness to heat and touch
Hand and feet numbness and paralysis; painless ulcers on soles of feet
Enlarged nerves that are hard and tender to touch (ulnar, posterior tibial, external popliteal)
Saddle-nose deformity, epistaxis
Imaging
N/A
Laboratory and Radiographic Testing
Diagnosis made primarily on clinical findings
Skin, earlobe, nerve, or nasal mucosa smear/biopsy for M. leprae (acid-fast staining)
Isolation of M. leprae from conjunctival tissue, scleral nodules, aqueous, or iris tissue
Differential Diagnosis
- Chronic granulomatous iridocyclitis
Sarcoidosis
Lyme disease
Syphilis
Tuberculosis (TB)
Herpesviruses
- Skin lesions can vary widely; some top differentials include:
Allergic contact dermatitis
Neurofibromatosis
Lupus vulgaris (cutaneous TB)
Systemic lupus erythematosus
Cutaneous sarcoidosis
Lichen planus
Psoriasis
Granuloma annulare
Onchocerciasis
Leishmaniasis
Tinea versicolor
Tinea corporis
Syphilis
Treatment
Early treatment of leprosy reduces ocular involvement
- Multi-drug therapy (MDT) is curative after 1–2 years, involving 2 or 3 of the following depending on the form and severity of leprosy
Rifampicin
Dapsone
Clofazimine
Referral/Comanagement
Infectious disease
Dermatology