“…Indeed, nursing observations of untreated subject 1 report cutaneous erythema and suspected heat intolerance during a very hot day. The present findings, therefore, reaffirm the value of early diagnosis and dietotherapy in phenylketonuria (9,23), as evidenced by the normal temperature-regulating ability (22,25) of the present treated, as compared with the untreated, subjects. This conclusion is further supported by the lack of history of heat or cold intolerance in these treated PKUs.…”