I believe it is likely a tie between "lymphangioleiomyomatosis" and "laryngotracheobronchitis," each at 24 letters.
There are only two letters starting with L that I can think of; the Letter of the alphabet, which is "L" and the Word "Letter." As "Letter" is longer than "L" I can only assume that the word "Letter" is the longest letter starting with L. lymphoblastic leukemia
The longest word starting with E is Electroencephalographically.
Floccinaucinihilipilification is the longest word starting with F; it means the act of estimating something as worthless.
Pneumonoultramicroscopicsilicovolcanoconiosis (also happens to be the longest word in the English language)
Extraterritoriality is the longest word in the English language beginning with "ex."
There are only two letters starting with L that I can think of; the Letter of the alphabet, which is "L" and the Word "Letter." As "Letter" is longer than "L" I can only assume that the word "Letter" is the longest letter starting with L. lymphoblastic leukemia
The longest word starting with E is Electroencephalographically.
Nonmodal is MAYBE the longest word.
Floccinaucinihilipilification is the longest word starting with F; it means the act of estimating something as worthless.
Lymphadenopathy
Pneumonoultramicroscopicsilicovolcanoconiosis (also happens to be the longest word in the English language)
Extraterritoriality is the longest word in the English language beginning with "ex."
Methionylthreonylthreonylglutaminylalanyl...isoleucine. It has 189819 letters and the longest word in the world.
The longest word starting with a "P" is pneumonoultramicroscopicsilicovolcanoconiosis, which has 45 letters and is in the Guinness Book of Records. It was, however, coined for the specific purpose of becoming the longest word, and is not a specifically recognized form of silicosis.
forethoughtfulness
Immunoelectrophoresis-- 21 letters
enormous