**8. Systemic involvement and special situations**

Overall, leprosy is a granulomatous inflammatory process. It causes intraneural pressure induced atrophy, palpable nerve thickening and progressive loss of neural functions with necrosis.

Histologically, there is epi-, peri- and endoneural fibrosis.

The most commonly affected nerve structures are: n. ulnaris located in the ulnar groove, n. medianus in the vicinity of the carpal tunnel, *n. tibialis* posterior, superficial branch of the radial nerve, sural nerve posteriorly of the malleolus, great auricular nerve as well as facial nerve, frontal and cervical branches.

Clinically, the resultant ocular muscle paralysis causes lagophthalmos, subsequently facilitating secondary corneal infections due to incomplete lid closure (Bell's palsy).

Sensory loss of the ophthalmic branch (V1) of the trigeminal nerve, too, results in corneal anesthesia, thus facilitating bacterial corneal ulceration.
