Leprosy: Year of the Zebra

Leprosy, also known as Hansen disease, is a chronic infectious disease caused by the bacteria Mycobacterium leprae and Mycobacterium lepromatosis. Likely transmitted through respiratory droplets from the nose or mouth during close contact with an affected individual, the bacteria mainly attack the skin and peripheral nerves but can also damage the eyes and upper respiratory tract mucosa. 

Now, the symptoms of leprosy vary depending on each infected individual’s immune response to the bacteria. Skin symptoms typically include lesions that can vary in appearance. The most common skin lesion includes well-demarcated lesions with central hypopigmentation that may become erythematous, or reddened, and raised due to skin inflammation. In some cases, nodules may also form. Other skin lesions may have a ‘punched out’ appearance or a ‘target-like’ appearance. Lesions are typically distributed randomly across the body.

Peripheral nerve symptoms can include hypoesthesia, or loss of sensation, and paralysis, typically of the hands and feet. If the nerves of the eyelid muscles or cornea are affected, paralysis of the eyelid may occur and lead to incomplete eyelid closure, or lagophthalmos; or corneal abrasion, ulceration, and even blindness. 

If the nasal mucosa is affected, a saddle-nose deformity, or a collapsed nasal bridge, may occur. 

Alright, so the diagnosis of leprosy is based on history, physical examination, and laboratory tests. A skin or nerve biopsy may be performed on affected areas looking for foam cells, or immune cells that have engulfed the bacteria but are unable to digest them; or for acid-fast bacilli that can be seen after staining.