https://en.wikipedia.org/wiki/Narcissistic_personality_disorder#CITEREFCaligorLevyYeomans2015

It is often co-morbid with other mental disorders and associated with significant functional impairment and psychosocial disability.[1]

It's a disability. People with NPD (that's person first language) struggle with identity, self-esteem regulation, skill development, and interpersonal problems. Both due to society's treatment of us, and the structure of our self-identity in the brain. I recommend reading the DSM-5's appendix on personality disorders. The new model of NPD is as a system of struggles with identity formation and interpersonal interaction.

https://www.psi.uba.ar/academica/carrerasdegrado/psicologia/sitios_catedras/practicas_profesionales/820_clinica_tr_personalidad_psicosis/material/dsm.pdf

For an egotypical, the process by which you made your identity as a child felt effortless, because of the support of your parents. And it's easy for you to imagine that it's that easy for everyone.

But I don't feel like a real person. My understanding of Myself is artificial. I made Myself up. And it's a fragile ego, so I frequently have to rebuild parts of it. I can change it without much effort. My way of interacting with the world is different than yours, because we both use our selves to do that, and how our selves function is different.

So basically NPD is neurodivergence because the brain works different. And we know the brain works different, because the mind works different.