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169
Etiology.
With regard to the predisposing and exciting causes of plantar
warts there has been much speculation, but no single causal factor
has been established.
Infection. If, as has been suggested by various observers, the
condition be due to a filter-passing virus, there should be present
some evidence of dissemination of infection by contagion or by
some medium conveying the infection.
Irritation. If, as Lake avers—
" The fundamental and underlying cause of verruca is
irritation "—
it is reasonable to expect that in a widespread outbreak among
school children some common irritative factor should be operative.
Injury. It is a well-recognised clinical fact that a plantar
wart often develops at the site of a previous puncture or abrasion
of the skin. MacLachlan has observed :—
" Some rubber contains spicules of steel which would wear
through and probably cause injury. . . . Children playing
on the sands get small particles of the sand or silica driven
into the skin and it is not uncommon to find plantar warts
apparently arising from such trivial injury."
Whitfield suggests trauma as a cause apart from infection :—
" They (warts) are most common in those who wear very
thin soles thus allowing the sole (of the foot) to be bruised
by gross unevenness of the ground, and in those who wear
boots with studs in the sole as is the case with football players."
Seasonal Prevalence. Eleven years' experience as a practising
chiropodist in Liverpool has led your Senior Chiropodist to associate
the autumn and early winter months with an increase in the number
of patients attending for treatment of plantar warts, but no statistical
evidence is available in support of this observation.