An autosomal recessive porphyria that is due to a deficiency of UROPORPHYRINOGEN III SYNTHASE in the bone marrow; also known as congenital erythropoietic porphyria. This disease is characterized by splenomegaly; anemia; photosensitivity; cutaneous lesions; accumulation of hydroxymethylbilane; and increased excretion of uroporphyrins and coproporphyrins.