M. leprae in Otolaryngology: An Overlooked Pathway to Blindness

An Overlooked Pathway to BlindnessMycobacterium leprae (M.leprae) is spread from nasal mucosa.It is not spread through the skin of infected patients.M. leprae infections can present to the otolaryngologist in the form of what appears to be 'atrophic rhinitis'.In advanced disease, they can also present with saddle nose deformities.If the ENT surgeon is oblivious of the manner M. leprae can present, then the diagnosis can be missed.M. leprae can present with hypopigmented patches and thickened cutaneous nerves, such as the greater auricular nerve (GAN).These hypopigmented patches are devoid of sensation.They are often termed anesthetic patches.These are pathognomonic of M. leprae infections.What is not well known is that M. leprae can present as 7th cranial nerve palsies.The exact pathophysiology happens when the malar skin gets infected via the nasal mucosa.The malar branch of the 5th cranial nerve gets involved.The malar division of the 5th cranial nerve anastomoses with the zygomatic branch of the 7th cranial nerve in the fibrous fascia in the malar region of the face.This leads to retrogressive infection of the 7th cranial nerve.The fibrous sheath over the malar region of the face gets edematous.This causes compression of the malar division along with that of the zygomatic branch of the 7th cranial nerve.This leads to lagophthalmos and diminished sensation over the cornea.This has the potential to causes blindness.Inability to close the eye (lagophthalmos), combined with diminished corneal sensation, can result in corneal ulceration, which in turn may lead to blindness.This serious consequence can be prevented by accurate diagnosis and timely treatment.