Ptyrss lb s skn cndtn, typ f drmtts, cmmnly sn n chldrn nd yng dlts s dry, fn-scld, pl ptchs n th fc. t s slf-lmtng nd slly nly rqrs s f mstrzr crms.
Th cndtn s s nmd fr th fn scly pprnc ntlly prsnt (ptyrss), nd lb (Ltn fr wht) rfrs t th pllr f th ptchs tht dvlp. Th ptchs r nt ttlly dpgmntd.