The diagnosis is normally made based upon the clinical appearance and history. Tissue biopsy is not usually indicated unless there are areas of ulceration or localized erythroplakia (red patches). The differential diagnosis is with other causes of white lesions (see leukoplakia for a more complete discussion). Specific conditions which can produce a similar appearance include Darier's disease, discoid lupus erythematosus, oral candidiasis, and oral lichen planus. If a biopsy is taken, the histopathologic appearance is one of hyperkeratosis and acanthosis. There may be squamous metaplasia of excretory ducts, which results in the visible papules if the ducts become hyperplastic. Neutrophils may fill some ducts. It is characterized as a "fissured" or "dried mud" appearance from excess keratin production by cells. Dysplasia is rarely seen.
Stomatitis nicotina
Bradyphrenia
Tinea faciei
Tinea imbricata
Visceral larva migrans
Allochiria
Acheiria
Tinea capitis