Tiêu đề 21. COMMONLY OCCURRING COMMUNICABLE DISEASES - LEPROSY.pdf ✅

PHARMD GURU Page 1 LEPROSY INTRODUCTION: Leprosy (also known as Hansen’s disease) is an infection caused by slow- growing bacteria called Mycobacterium leprae or M. lepromatosis bacteria. It is a slowly developing (from six months to 40 years), progressive disease that damages the skin and nervous system. It results in skin lesions and deformities, most often affecting the cooler places on the body (for example, eyes, nose, earlobes, hands, feet and testicles). The skin lesions and deformities can be very disfiguring and are the reason that infected individuals historically were considered outcasts in many cultures. Although human-to-human transmission is the primary source of infection, three other species can carry and (rarely) transfer M. leprae to humans: chimpanzees, mangabey monkeys, and nine-banded armadillos. The disease is termed a chronic granulomatous disease, similar to tuberculosis, because it produces inflammatory nodules (granulomas) in the skin and nerves over time. The disease has been known to man since time immemorial. DNA taken from the shrouded remains of a man discovered in a tomb next to the old city of Jerusalem shows him to be the earliest human proven to have suffered from leprosy. The remains were dated by radiocarbon methods to 1–50 A.D. The disease probably originated in Egypt and other Middle Eastern countries as early as 2400 BCE. An apparent lack of knowledge about its treatment facilitated its spread throughout the world. Mycobacterium leprae, the causative agent of leprosy, was discovered by G. H. Armauer Hansen in Norway in 1873, making it the first bacterium to be identified as causing disease in humans. Over the past 20 years, the WHO implementation of MDT has rendered leprosy a less prevalent infection in 90% of its endemic countries with less than one case per 10,000 populations. Though, it continues to be a public health problem in countries like Brazil, Congo, Madagascar, Mozambique, Nepal, and Tanzania. CLASSIFICATION: Leprotic patients can be classified into three groups, each with slightly different signs and symptoms: COMMONLY OCCURRING COMMUNICABLE DISEASES
PHARMD GURU Page 2 PAUCIBACILLARY (PB), OR TUBERCULOID, HANSEN’S DISEASE: It is characterized by one or a few hypopigmented or hyperpigmented skin macules that exhibit loss of sensation (anesthesia) due to infection of the peripheral nerves supplying the region. The body’s immune response may also result in swelling of the peripheral nerves; these enlarged nerves may be palpated under the skin, and may or may not be tender to the touch. The nerves most often found to have swelling are:  Great auricular nerve,  Ulnar nerve above the elbow and dorsal cutaneous branches at the wrist,  Median nerve at the wrist (in the carpal tunnel),  Radial nerve (superficial at wrist),  Common peroneal nerve (also femoral cutaneous and lateral popliteal nerves where they wind around the neck of the fibula),  Posterior tibial nerve, posterior to the medial malleolus,  Sural nerve. MULTIBACILLARY (MB), OR LEPROMATOUS, HANSEN’S DISEASE: It is characterized by generalized or diffuse involvement of the skin, a thickening of the peripheral nerves under microscopic examination, and has the potential to involve other organs, the eyes, nose, testes and bone. The nodular form of this condition is the most advanced form of the disease. Ulcerated nodules contain large numbers of M. leprae acid-fast bacilli packed in macrophages that appear as large foamy cells. MB form of Hansen’s disease is associated with:  Multiple, symmetrically-distributed skin lesions that might not exhibit loss of sensation,  Nodules and Plaques,  Thickened dermis,  Frequent involvement of the nasal mucosa resulting in nasal congestion and epistaxis. BORDERLINE, OR DIMORPHOUS, HANSEN’S DISEASE: It is the most common form. When compared to tuberculoid or lepromatous forms, it is of intermediate severity. The skin lesions seem to be of the tuberculoid type, but
PHARMD GURU Page 3 are more numerous, and may be found anywhere on the body. Peripheral nerves are affected as well, with ensuing weakness and anesthesia. PATHOGENESIS OF LEPROSY: Onset of leprosy is insidious. It affects nerves, skin and eyes. It may also affect mucosa (mouth, nose and pharynx), testes, kidney, voluntary/smooth muscles, reticuloendothelial system, and vascular endothelium. Bacilli enter the body usually through respiratory system. It has low pathogencity, only a small proportion of infected people develop signs of the disease. Though infected, majority of the population do not develop the disease. After entering the body, bacilli migrate towards the neural tissue and enter the Schwann cells. Bacteria can also be found in, macrophages, muscle cells and endothelial cells of blood vessels. After entering the Schwann cells or macrophage; fate of the bacterium depends on the resistance of the infected individual towards the infecting organism. Bacilli start multiplying slowly (about 12-14 days for one bacterium to divide into two) within the cells, get liberated from the destroyed cells and enter other unaffected cells. Till this stage, person remains free from signs and symptoms of leprosy. As the bacilli multiply, bacterial load increases in the body and infection is recognized by the immunological system. Lymphocytes and histiocytes (macrophages) invade the infected tissue. At this stage, clinical manifestation may appear as involvement of nerves with impairment of sensation and/or skin patch. If it is not diagnosed and treated in the early stages, further progress of the diseases is determined by the strength of the patient’s immune response. Specific and effective cell mediated immunity (CMI) provides protection to a person against leprosy. When specific CMI is effective in eliminating/ controlling the infection in the body, lesions heal spontaneously or it produces pauci-bacillary (PB) type of leprosy. If CMI is deficient; the disease spreads uncontrolled and produces multi bacillary (MB) leprosy with multiple system involvement. Sometimes, the immune response is abruptly altered, either following treatment (MDT) or due to improvement of immunological status, which results in the inflammation of skin or/and nerves and even others tissue, called as leprosy reaction (types 1 and 2).