Phenotypes and endotypes
The concepts of phenotype and endotype have been increasingly used to
characterize variants under a wider disease umbrella, referring to
either the apparent differentiating features (phenotype) or the
underlying mechanisms (endotype). While disease variability is clearly
the norm rather than the exception in regards to most allergic diseases,
the realization that treatment response may vary radially between
groups, has given impetus to this approach [23]. Unfortunately, lack
of pathognomonic biomarkers, considerable overlap and unstable temporal
dynamics have not allowed, for the time being, the construction of
conclusive phenotype and/or endotype-based guidelines [24].
Nevertheless, clear distinctions and differentiating factors can be
drawn, such as the hormonal or gustatory rhinitis – all part of the
non-allergic rhinitis spectrum. A distinct pediatric example is rhinitis
in infants, which presents additional challenges in management choices,
requiring further evidence [25].