Clinical, histopathological, and biological attributes of prurigo pigmentosa are distinctive and, inevitably, one day the cause of it will be known. In patients in whom the claim was made of an association of prurigo pigmentosa with ketonuria, the time of follow up was either short, that is, only eight months, or was not given at all. In 12 of the patients, treatment successfully with dapsone or minocycline was indicated, thereby permitting the inference that improvement of the skin lesions was related to the medication rather than to a change in status metabolically. None of the studies about ketonemia in patients with prurigo pigmentosa provide any information about the frequency of ketosis in the normal population. Dieting is common.

At the moment, all of the factors mentioned as being causative of prurigo pigmentosa, from sweating to ketonemia, are mere suppositions.