Leprosy (overview) A30.9

Important, chronic granulomatous infectious disease caused by Mycobacterium leprae and Mycobacteriumlepromatosis(see belowMycobacterium leprae), with preferential infestation of skin and peripheral nerves and of low contagiousness. While leprosy no longer plays a role in industrialized countries, it is still of great medical importance in developing countries. Infection and manifestation of the disease occurs mainly in populations with malnutrition, poor general health and immunodeficiencies. Leprosy is still a stigmatising disease; sufferers still have to fear exclusion from the community and family.

Reminder. Obligation to report!

Mycobacterium leprae (immobile, gram-positive, acid-fast rods). The pathogens are often arranged intracellularly in bundles. Very slow growth.

Classification based on immunological, clinical, bacteriological and histological findings (see also Table 1). A distinction is made between:

Leprosy indeterminata

Leprosy lepromatosa - LL- (pathogen-rich, anergic, spots, papules, plaques and nodules)

Borderline leprosy

• Borderline leprosy lepromatosa -BL- (pathogen-rich, plaques and spots, tendency to symmetry of lesions)
• Mid Borderline Leprosy lepromatosa -BB- ( pathogen-rich, asymmetry of foci)
• Boderline leprosy tuberculoides - BT- (pathogen-poor, asymmetrical, few plaques, satellites)

Leprosy tuberculoides -TT- (no pathogens detectable, 1-5 sharply demarcated plaques, hypopigmented, asymmetric).

Intermediate le prosy -I- (Intermediate leprosy; 1 or few, hypopigmented, patches no plaques).

Therapeutic relevance is the determination of the microscopic bacterial quantity or density, e.g. by nasal swab. The bacterial index (bacterial density per field of view) is classified in the following way:

• Index 6: more than 1000 bacteria per field of view (Gf.),
• Index 5: between 100 and 1000 bacteria per gf,
• Index 4: between 10 and 100 bacteria per gf,
• Index 3: between 1 and 10 bacteria per gf,
• Index 2: between 1 and 10 bacteria per 10 gf,
• Index 1: between 1 and 10 bacteria per 100 gf,
• Index 0: 0 bacteria in 100 gf.

In 2015, 211,973 new cases of leprosy were diagnosed worldwide. Currently, most new cases (>96%) were registered in the 22 high-risk countries (lepra priority countries) (WHO Fact Sheets 2017). Leprosy remains a disease of poverty rather than a disease of tropical or subtropical countries (endemic areas: India, Brazil, Bolivia, Indonesia, South Sudan, Sierra Leone). Malnutrition, poor nutrition, poor AZ, immunodeficiency, favour its outbreak.

Distribution: In a larger Indian collective (n=220), the following distribution was found:

• Multibacillary leprosy: w>m. It was more prevalent in villagers (80.9%) than in urban dwellers (64.8%).
• Borderline lepromatous leprosy (38.2%)
• Lepromatous leprosy (28.2%)
• Borderline tuberculoid leprosy (21.4%) (Arif T et al 2019).

The average age in a larger Indian study (Arif T et al. 2019) was between 20 and 40 years. Childhood or adolescence may also be affected.

Incubation period: 3 to about 20 years; uncharacteristic early symptoms.

Skin symptoms: leprosy lepromatosa, leprosy tuberculoides, leprosy indeterminata, dimorphic leprosy. Depigmentation or hypopigmentation of the skin.

Sensitivity disorders: hyperaesthesia, paraesthesia, hypaesthesia, anaesthesia. Thickening of nerves, often of the ulnar nerve.

Sensory disturbances: Disturbance of the sensation of temperature, pain and touch.

Pathogen detection:

• Direct: smear of skin (forehead, auricle, trunk, extensor sides of extremities) and nasal mucosa, skin or nerve biopsies, Faraco-Fite stain; Ziehl-Neelsen stain.
• Cultural: breeding only by transfer to animals, esp. mice, armadillos, chipmunks, hedgehogs. Altogether difficult and not very promising.

Lepromin reaction: For individual leprosy classification and prognosis.

Histamine test: Intracutaneous application of histamine - lack of reflex erythema.

Sweat test: Absence of sweat secretion in lepromatous foci; see also Minor sweat test.

PGL I antibody: Detection of specific antibodies against PGL I antigen.

Remember! It is important to monitor and treat secondary infections, as these are often the cause of the death of leprosy patients!

• Pregnancy: Leprosy bacteria reach the unborn child via the placenta. Therefore, treatment must be carried out in any case during pregnancy. Teratogenic effects of the leprosy medication are not yet known. Dapsone, rifampicin as well as clofazimine are placental.
• Rehabilitation: Subsequent rehabilitation measures according to the clinical symptoms of the patient, such as plastic reconstructive surgery and physiotherapy.

More favourable in tuberculoid leprosy,The immune status of the patient is decisive for the course of leprosy! In poor immune status, there is a strong multiplication of pathogens; development of leprosy lepromatosa with unfavourable prognosis. Favourable prognosis in tuberculoid leprosy. Further impairment by secondary infections.

Clarification. Since the contagiousness is low and the antibiotic therapy is successful, strict isolation of the sick is no longer required today. It is important to improve the hygienic conditions and to check contact persons regularly (every 6 months). If necessary, a single administration of rifampicin after exposure can suppress the manifestation of a disease.

Characteristics of the leprosy forms

Leprosy treatment

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