While porphyria cutanea tarda and porphyria variegata are independent diseases, we report on seven rare cases with a coincidence of these two different porphyrias in one individuum. The mutual clinical symptom was a cutaneous photosensitivity, which is a major symptom in porphyria cutanea tarda and a facultative one in porphyria variegata. Additionally, five patients had also experienced episodes of acute abdominal pain, which were in three cases accompanied by neurological symptoms, thus offering evidence for an acute hepatic porphyria, such as porphyria variegata. Determination of urinary porphyrin metabolites revealed a porphyria cutanea tarda-like excretion pattern with an elevation of uroporphyrin (mean 1134 nmol/24 h, range 563-4052, normal < or = 30) and heptacarboxyporphyrin (mean 389 nmol/24 h, range 64-830, normal < or = 4). In all patients, however, urinary coproporphyrin was also increased, reaching levels too high for porphyria cutanea tarda but typical for porphyria variegata (mean 1788 nmol/24 h, range 142-4168, normal < or = 120). Fecal porphyrin excretion also resembled the variegate-type with a high concentration especially of protoporphyrin (mean 628 nmol/g dry weight, range 401-1018, normal < or = 151), accompanied by an increase of coproporphyrin (mean 194 nmol/g dry weight, range 75-409, normal < or = 37). The urinary porphyrin precursors 5-aminolaevulinic acid and porphobilinogen were markedly elevated only in one patient, who was in an acute porphyric phase at the time of investigation. The activity of uroporphyrinogen decarboxylase in erythrocytes was considerably decreased in six of our cases (33-64%) and slightly diminished in the other one (83% of normal activity).(ABSTRACT TRUNCATED AT 250 WORDS)