Introduction

Leprosy, also known as Hansen’s disease, is a chronic infectious condition that primarily affects the skin and peripheral nerves and is caused by the bacterium Mycobacterium leprae. Early diagnosis is crucial to prevent irreversible disabilities, but the disease’s initial signs and symptoms are often subtle and easily overlooked, leading to delayed detection and increased risk of complications. In this article, we will delve into the early diagnostic signs and symptoms of leprosy.¹

Common early signs and symptoms

Some common signs and symptoms are typically observed in a few key areas of the body.^1,2,3,4

Cutaneous manifestations

The most frequent early signs are:

• Skin-related, including hypopigmented or erythematous patches
• Painless and non-itchy skin lesions
• Nodules
• Loss of eyebrow or eyelash hair

These cutaneous symptoms account for the majority of early presentations in both adults and children, with hypochromic and anaesthetic skin infiltration being common in pediatric cases.

Neurological symptoms

Early nerve involvement may present as:^1,2

• Numbness
• Neuritis
• Thickened peripheral nerves
• Facial paralysis
• Motor dysfunction

Numbness is a particularly common early symptom and is often associated with delayed diagnosis and a higher risk of disability.

Other features

Less common early signs include congestion of the nasal mucosa and systemic manifestations such as muscle atrophy or finger contracture (Dupuytren's contracture).

Diagnosing leprosy

Diagnosing leprosy usually starts with a clinical examination, where a doctor assesses a patient's physical signs. In more challenging cases, laboratory tests and imaging might be necessary to confirm the diagnosis, such as histological tests, alongside ultrasound and MRI for early nerve damage. Biomarker research can also be conducted, such as blood RNA signatures (e.g., RISK4LEP), which can predict leprosy years before symptoms.^1,5

Leprosy primarily affects the skin and peripheral nerves. Doctors look for at least one of these key signs to diagnose the disease:

• Skin patches with sensory loss: this means a pale (lighter than your natural skin tone) or reddish skin patch where you cannot feel touch, temperature, or pain
• Thickened nerves with numbness or weakness: a nerve that feels enlarged, accompanied by a loss of feeling or muscle weakness in the area that the nerve controls
• Presence of bacteria in a skin smear: a lab test of a skin sample might reveal the leprosy-causing bacteria under a microscope

Once diagnosed, leprosy cases are categorised into two types for treatment planning:

• Paucibacillary (PB) leprosy: this type involves one to five skin lesions and no detectable bacteria in a skin smear
• Multibacillary (MB) leprosy: this type is diagnosed if you have more than five skin lesions, nerve involvement (even if there are no skin lesions), or bacteria present in a skin smear, regardless of how many skin lesions you have

Diagnostic challenges

• Overlap with other conditions: early skin lesions can resemble other dermatological diseases, such as vitiligo, making clinical diagnosis challenging, especially in atypical areas 
• Delayed recognition of nerve symptoms: nerve-related symptoms are frequently overlooked, leading to longer diagnostic intervals and increased risk of irreversible neuropathy and disability 
• Paediatric considerations: in children, early signs are often missed, emphasising the need for careful examination of contacts in households with known leprosy cases^2,3,6,7,8,9

Importance of awareness

Early leprosy often presents with subtle skin changes and sensory disturbances, which are frequently missed or mistaken for other conditions. Nerve symptoms, though less common initially, are critical indicators and are linked to delayed diagnosis and disability. Improved awareness, targeted screening, and emerging biomarker-based tools are key to enhancing early detection and reducing the burden of leprosy-related complications.

Understanding these signs and promoting education, we can significantly improve outcomes for individuals affected by this ancient yet curable disease.^2,3,6

FAQs

What are the earliest signs of leprosy to look out for?

Pale (hypopigmented) or reddish skin patches that have lost sensation to touch, temperature, or pain. Other common early indicators include thickened or enlarged peripheral nerves accompanied by numbness or muscle weakness, especially in the hands and feet. Less common signs can involve nasal congestion or changes to eyebrow/eyelash hair. Early detection is key to preventing long-term disabilities.

How is leprosy accurately diagnosed?

Leprosy is primarily diagnosed through a clinical examination by a healthcare professional, who looks for the cardinal signs, like sensory loss in skin patches or thickened nerves. In some cases, a skin smear is performed to microscopically detect the presence of Mycobacterium leprae bacteria, the cause of leprosy. 

Why is early diagnosis so important?

Early diagnosis is important because it allows for prompt treatment, which can prevent irreversible nerve damage, deformities, and disabilities. Delaying diagnosis increases the risk of serious complications and lifelong challenges.

Is leprosy still common today, and can it be cured?

While leprosy is much less common globally than in the past, it still exists in many parts of the world, particularly in tropical and subtropical regions. It is important to note that leprosy is curable with multi-drug therapy (MDT), a combination of antibiotics that effectively kills the bacteria. With early diagnosis and consistent treatment, people with leprosy can be cured and lead full, healthy lives, preventing the progression of the disease and its associated disabilities.

Summary

Leprosy, or Hansen’s disease, is a long-lasting infection caused by the bacterium Mycobacterium leprae, primarily affecting the skin and peripheral nerves. Early diagnosis is essential to avoid lasting disabilities, but initial symptoms can be subtle and often go unnoticed, leading to delays in detection and complications. Common early signs include skin-related symptoms such as pale or reddish patches, painless non-itchy lesions, nodules, and loss of eyebrow or eyelash hair. In children, hypochromic and anaemic skin infiltration is often seen. Neurological symptoms may appear as numbness, thickened peripheral nerves, neuritis, facial paralysis, and motor dysfunction. Numbness is particularly prevalent and indicates a higher risk of disability. Other less typical symptoms include nasal congestion and muscle atrophy.

Diagnosis starts with a clinical examination to identify key signs, which may include skin patches with sensory loss, thickened nerves accompanied by numbness or weakness, and the presence of leprosy bacteria in a skin smear. Leprosy is categorised into two types for treatment: paucibacillary (PB) and multibacillary (MB). Challenges in diagnosis arise due to similarities with other skin conditions and overlooked nerve symptoms, especially in children, highlighting the need for careful examination in households with known leprosy cases. Increased awareness and targeted screening can improve early detection and significantly enhance outcomes for those affected by this curable disease.