Leprosy, Hansen’s diseases - Introduction, Pathogenesis, Symptoms, Clinical Forms
Introduction to Leprosy / Hansen’s disease
Leprosy / Hansen’s disease is a chronic granulomatous disease primarily affecting the skin, peripheral nerves, and mucosa of the upper respiratory tract (URT). Granulomatous – refers to granulomas which are lesions of epithelial macrophages.
The clinical symptoms change depending on the immune state of the patients. It is caused by Mycobacterium leprae, an NTM (non-tuberculosis mycobacteria)
Pathogenesis of Leprosy / Hansen’s disease
The incubation period of Leprosy / Hansen’s disease varies from weeks to years. The infection starts from nasal droplets or unknown exposure to an infected person. The generation time of the bacterium is 14 days.
Mycobacterium leprae infects Schwann cells in nerves leading to demyelination (damage of myelin) sheath thereby damaging the nerve cells and loss of sensitivity. Involvement of mucosal cells leads to disfigurement and erythematous and macules appear on the skin due to loss of pigmentation.
The cardinal signs of Leprosy / Hansen’s disease
Following are the cardinal signs of Leprosy / Hansen’s disease.
Hypoesthesia (reduced sense of touch)
skin lesions
loss of hair, sweating, and peripheral neuropathy
the first physical sign of leprosy is usually cutaneous
the subtype of leprosy often determines the degree of skin involvement
Diagnosis is based on one or more of 3 signs
Hypopigmentation or erythematous macules with sensory loss
Thickened peripheral nerves
A positive acid-alcohol fast smear
Clinical forms of leprosy / Hansen’s disease
Ridley-Joping classification of leprosy / Hansen’s disease are the clinical forms.)
Lepromatous leprosy
Tuberculoid leprosy
Borderline or dimorphous leprosy
Interminant leprosy
Mid-borderline leprosy