is an expression which presents the most extreme example for something from within a specific category. Due to this, it will usually be translated as 'when it comes to (A), (B)', 'in particular to (A) is (B)', or 'with (A) as the most extreme example, (B)'.
This is a combination of the case-marking particle に, the て-form of the る-Verb 至（いた）る 'to climax', or 'to culminate in', and the adverbial particle
は in its standard role of presenting a topic. In this way, the literal meaning of 'culminating within (A) is (B)' is quite close to the nuance of the English translations.
will appear following nouns, or nominalized phrases.
My whole family is mechanically illiterate. What's more, my mother can't even use the internet.
Recently, employees here are unmotivated. As for Fujita-san, their computer isn't even turned on.
My kanji test's score was 49. What's worse is that my listening score was 20.
As the verb 至（いた）る itself is used to present extreme examples or locations that are considered to be right 'on the precipice' of something, に至（いた）っては
will primarily present things that are surprising or astonishing in some way. This is primarily only used when the example itself is quite negative or unfavorable.
I heard that the second son of the family over there flunked. As for their eldest son, I heard that he was at the top of his grade.