Discussion
Definition of a comprehensive pathophysiological
description of dandruff and seborrheic dermatitis
The signs and symptoms of the D/SD conditions are
well established mainly through traditional (macro) assessment
of the scalp skin condition. The description of
the scalp condition at the structural and molecular level
is now enabled by new molecular measurement capabilities.
The pathophysiological model that is emerging
(Fig. 1) is based on the established etiological phases
of Malassezia metabolism initiating the inflammatory
cascade, resulting in scalp skin hyper-proliferation and
incomplete corneocyte differentiation that yields an
impaired SC barrier.
Measures at the structure/function level, such as
epidermal morphology, Malassezia infiltration and
instrumental assessments related to moisture content
have supported the basic etiology sequence discussed
above. These measures have enabled a deeper understanding
of the pathophysiology of these conditions by
demonstrating that the superficial signs and symptoms
are the result of an irregular epidermal construction
and resultant dis-organization in the onset of D/SD.
These observations, in turn, have led to probing specific
molecular mechanisms in the skin, which established
the inflammatory nature of the condition, the poor synchronization
of proliferation and differentiation and the
relatively ineffective barrier function.
Rather than describing a healthy scalp as simply being
free from signs and symptoms of a condition, these new
parameters enable both a more complete pathophysiological
description of D/SD as well as establishing more
specific criteria for assessing whether the condition has
been effectively treated.