Chalazion is/are a) True meibomian cyst b) Mucous cyst c) Sebaceous cyst d) Cyst of hair follicle e) Obstruction of meibomian gland
**Core Concept**
A chalazion is a type of eyelid lesion that results from the obstruction of a meibomian gland, leading to a localized granulomatous inflammation and the formation of a cyst-like structure.
**Why the Correct Answer is Right**
The correct answer is **e) Obstruction of meibomian gland** because a chalazion occurs when a meibomian gland, which produces sebum, becomes clogged and inflamed. This leads to the accumulation of sebum and the formation of a granulomatous cyst. The meibomian glands are specialized sebaceous glands located in the tarsal plate of the eyelid, and their obstruction is the primary cause of chalazion formation.
**Why Each Wrong Option is Incorrect**
* **Option A:** A true meibomian cyst is a rare condition where a meibomian gland becomes cystic, but this is not the same as a chalazion, which is an inflammatory reaction to gland obstruction.
* **Option B:** A mucous cyst is a different type of eyelid lesion that occurs in the conjunctiva or caruncle, and is not related to meibomian gland obstruction.
* **Option C:** A sebaceous cyst is a general term for a cystic lesion filled with sebum, but it is not specific to the eyelid or meibomian gland obstruction.
* **Option D:** A cyst of a hair follicle, also known as a steatocystoma, is a different type of skin cyst that occurs in the hair follicle, and is not related to meibomian gland obstruction.
**Clinical Pearl / High-Yield Fact**
A chalazion can be differentiated from a hordeolum (stye) by its location and size. A chalazion typically occurs in the tarsal plate of the eyelid, while a hordeolum occurs in the hair follicle or meibomian gland of the eyelid margin.
**Correct Answer:** e. Obstruction of meibomian gland.