Juvenile hemochromatosis (JH) is a characteristic form of genetic hemochromatosis with an early onset and severe clinical course leading to death if iron depletion treatment is not timely applied. Clinical complications include liver cirrhosis, heart failure, hypogonadotropic hypogonadism, and diabetes. In the present study we report the first case of JH described in Spain. Biochemical and genetic characteristics of the patient and relatives (parents and siblings) were investigated. No individual presented either the mutation at position 845 of the HFE gene or at position 750 of the TFR2 gene, associated with other types of hemochromatosis. Nevertheless, some individuals were homozygous for the mutation at position 187 of HFE. The hypothetic region of association with JH, located at chromosome 1q, was also investigated and results show that the patient presented a unique genotypic combination in 1q. The only brother with heavy iron deposits in hepatocytes was found to be heterozygous for the JH-associated region and homozygous for the HFE187 gene, suggesting a synergistic effect between both hemochromatosis-associated genes.