Overview

Leprosy, also known as Hansen’s disease, is a chronic infectious disease caused by the bacterium Mycobacterium leprae. It primarily affects the skin, peripheral nerves, mucous membranes of the respiratory tract, and eyes. Leprosy has been historically misunderstood, but modern medical advances have made it both preventable and curable. The disease progresses slowly, with symptoms appearing years after the initial infection. Early diagnosis and treatment are key to preventing disability and transmission.

Causes

The primary cause of leprosy is infection with the slow-growing bacterium Mycobacterium leprae. The disease is believed to spread through respiratory droplets from the nose and mouth of untreated individuals. It is not highly contagious and requires prolonged, close contact to transmit. Other contributing factors include:

• Genetic susceptibility: Some individuals have genetic traits that make them more susceptible to infection.
• Environmental exposure: Living in areas with high endemicity increases risk.
• Immunocompromised status: People with weakened immune systems may be more likely to develop the disease after exposure.

Symptoms

Leprosy presents a wide range of symptoms depending on the form and severity of the disease. Common symptoms include:

• Skin lesions: Patches of skin that are lighter or reddish than the surrounding area, often with reduced sensation.
• Numbness: Loss of sensation in hands, feet, arms, or legs due to nerve damage.
• Muscle weakness: Especially in the hands and feet, leading to deformities over time.
• Thickened nerves: Enlargement of peripheral nerves, commonly near the elbows, knees, or around the neck.
• Eye problems: Dry eyes, reduced blinking, or blindness in severe cases if the facial nerve is involved.
• Nasal congestion or nosebleeds: Due to involvement of the nasal mucosa.
• Ulcers on the soles of the feet or hands: Resulting from unnoticed injuries due to sensory loss.

Diagnosis

Diagnosing leprosy involves clinical evaluation and laboratory tests:

• Physical examination: Doctors look for characteristic skin lesions and test areas for loss of sensation.
• Skin smear test: A sample taken from the skin is examined under a microscope for Mycobacterium leprae.
• Skin biopsy: A small tissue sample may be taken for histopathological examination.
• Lepromin skin test: Sometimes used to classify the type of leprosy, though it is not a diagnostic tool.
• PCR testing: Advanced molecular tests can detect the DNA of the bacteria in difficult cases.

Treatment

Leprosy is completely curable with multidrug therapy (MDT), which is provided free of charge in many countries by the World Health Organization (WHO). Treatment options include:

• Multidrug therapy (MDT): A combination of antibiotics such as rifampicin, dapsone, and clofazimine administered for 6-12 months or longer depending on disease classification.
• Anti-inflammatory medications: Corticosteroids or thalidomide may be prescribed to manage nerve pain or inflammation (lepra reactions).
• Treatment of complications: Specialized care may be needed for ulcers, nerve damage, and deformities.
• Rehabilitation: Physiotherapy and surgical correction may be necessary in advanced cases to improve mobility and quality of life.

Prognosis

With early diagnosis and appropriate treatment, the prognosis for leprosy is excellent. Most patients are no longer infectious within days of starting treatment, and progression of the disease halts. Individuals who receive timely treatment usually recover fully without disability.

However, if left untreated, leprosy can cause permanent nerve damage, severe disability, blindness, and social stigma. Early treatment significantly reduces these risks. Global health initiatives have made leprosy rare in many parts of the world, and ongoing public health efforts continue to reduce transmission and improve outcomes for those affected.