SNP Shot: Genomic Insights

Leprosy, also known as Hansen's disease, is an ancient ailment caused by the bacterium Mycobacterium leprae. It is a contagious disease, meaning it can spread from person to person. Transmission typically occurs through inhaling airborne droplets released when infected individuals cough or sneeze, or through contact with their nasal fluids. However, leprosy is not easily spread; about 95% of people exposed to Mycobacterium leprae do not develop the disease. Infection can occur at any age, and symptoms may appear months or even decades after exposure (ranging from several months to 20 years).

Leprosy primarily affects the skin and peripheral nerves, which connect the brain and spinal cord to muscles and sensory receptors for touch, pain, and temperature. Most people with leprosy experience skin lesions (cutaneous lesions) and nerve dysfunction (peripheral neuropathy), although the severity and extent of these issues vary significantly. Leprosy presents on a spectrum, with multibacillary (or lepromatous) leprosy being the most severe form and paucibacillary (or tuberculoid) leprosy the least severe. Intermediate forms, exhibiting a mix of symptoms from both types, are sometimes referred to as borderline forms.

Multibacillary leprosy is characterized by numerous skin lesions, including surface damage and lumps (nodules) beneath the skin. The mucous membranes lining body openings such as the eyelids, nose, and mouth can also be affected, potentially leading to vision loss, nasal tissue destruction, or speech impairment. In some cases, internal organs and tissues may also be damaged. Nerve damage in multibacillary leprosy often causes a loss of sensation in the hands and feet. This lack of sensation can lead to repeated, unnoticed injuries that, if left untreated, can result in the body reabsorbing affected fingers or toes, causing shortening or loss of these digits.

Paucibacillary leprosy typically involves only a few skin lesions. While sensation is generally lost in these affected areas, the more severe signs and symptoms seen in multibacillary leprosy are less common in this form of the disease.

Regardless of the type of leprosy, individuals can experience episodes known as reactions, which can cause further nerve damage. These reactions include reversal reactions, characterized by pain and swelling of skin lesions and nerves in the hands and feet. Individuals with more severe forms of leprosy may develop erythema nodosum leprosum (ENL), which involves fever and painful skin nodules, as well as painful, swollen nerves. ENL can also cause inflammation in the joints, eyes, and testicles in men.

Leprosy has historically been associated with stigma due to its infectious nature and potential for disfigurement, leading to social and emotional difficulties for those affected. However, modern treatments can effectively halt the progression of leprosy and prevent its spread. While the infection itself is curable, nerve and tissue damage that occurred before treatment is typically irreversible.

Inheritance:

Leprosy itself is not directly inherited. However, genetic factors can influence an individual's susceptibility to contracting leprosy if exposed to Mycobacterium leprae. A tendency to develop leprosy can run in families, but the specific inheritance pattern remains unclear.