In recognition of World Leprosy, join Charlie Dunn, MD, for this episode of Topical Conversations to hear a dermatologist’s overview of leprosy, shedding light on the progress made, emerging insights, and the vital role dermatologists play in recognizing, treating, and caring for patients affected by this rare disease. 

Reviewing the basics 

Leprosy, also known as Hansen's disease, is caused by the slow-growing mycobacterium leprae complex, which tends to involve the skin and peripheral nerves. 

The global health perspective 

Despite tremendous advancements in recognition and treatment, leprosy remains a significant global health concern. Annually, approximately 200,000 cases are diagnosed worldwide. 

The United States, while experiencing relatively low case counts, has seen a notable geographical incidence shift, particularly in the southeast. In 2020, more than one-fifth of cases were identified in Florida, with 80% of those cases occurring in eastern Florida. The reasons behind the increase in geographic incidences are not yet identified but may be related to a shift in disease transmission. 

Disease transmission 

Due to the slow-growing nature of the bacteria, transmission is not fully understood. Transmission of leprosy is historically linked to genetic susceptibility and prolonged exposure to someone with untreated disease via respiratory droplets. 

However, there are an increasing number of cases in the US where close contact cannot be established. In these cases, transmission is thought to occur either through prolonged travel within countries with high rates of the disease or through zoonotic exposure. 

Zoonotic exposure is thought to be key to the increased prevalence of leprosy in the southeastern United States particularly via nine-banded armadillos, which are known reservoirs for mycobacterium leprae strains known to infect humans. 

Clinical presentation 

Leprosy manifests in diverse ways, largely depending on the bacteria burden and the infected person’s immune response. Clinical manifestations can be considered across 2 ends of a spectrum. One 

end is tuberculoid leprosy, where there is a robust immune response to the disease. These patients tend to have a small number of well-demarcated patches or plaques that are lightly pigmented, may be red or rust-colored in the center, and have a degree of sensation abnormalities. Patients may also present with poor hair growth or abnormal sweating. 

On the other end is lepromatous leprosy, where there is no apparent resistance to mycobacterium leprae. Patients present with poorly demarcated, nodular lesions on all parts of the body. 

With nerve involvement, patients may present with numbness or tingling of the hands and feet, tender, enlarged peripheral nerves, and lumps or swelling of the earlobes or face. If these nerve findings progress, they can lead to hand and foot weakness, facial paralysis, loss of eyelashes or eyebrows, and leonine facies. 

Diagnosing leprosy 

Diagnosis is established via a skin biopsy, ideally from the leading edge of a lesion that demonstrates the bacterial within a cutaneous nerve. In tuberculoid, or paucibacillary, leprosy, this can be challenging; multiple biopsies may be needed, and diagnosis may need to be inferred from clinical or histopathologic clues. 

One vital aspect of diagnosis to remember is that leprosy is a reportable condition at both the state and federal level. The National Hansen’s Disease Program (NHDP), once notified, provides telemedicine visits and medications for patients and professional consultation for clinicians, all at no cost. 

Treating leprosy

Contrary to popular misconceptions, leprosy is highly treatable, with patients becoming noninfectious within days after starting antibiotics. Monthly directly observed therapy (DOT) is recommended by the NHDP, consisting of treatment with rifampin, moxifloxacin or ofloxacin, and minocycline. 

A key unique component to treating leprosy is screening all patients, at the time of diagnosis, regularly during treatment, and after treatment, for immunologic reactions. These reactions can result in severe nerve injury if not treated promptly. 

Addressing the stigma 

Leprosy continues to carry societal stigma. Dermatologists play a crucial role in dispelling misconceptions, advocating against stigma, and promoting awareness at both individual and community levels. 

Key points 

• Increasing rates of leprosy have presented in the southeast US, particularly Florida, in recent years 
• Transmission is linked to close contact and zoonotic exposure 
• Diagnosis can be made via biopsy or inferred from clinical or histopathologic clues 
• Leprosy must be reported at the state and federal levels
• Directly observed therapy with rifampin, moxifloxacin or ofloxacin, and minocycline is recommended 
• Patients should be screened on an ongoing basis for immunologic reactions 
• Dermatologists play a crucial role in dispelling stigmas around leprosy