Final answer:
The symptoms described in the question, such as extreme photosensitivity, reddish-brown urine, and splenomegaly, are indicative of Erythropoietic Protoporphyria (EPP), a form of porphyria affecting the bone marrow and leading to a buildup of porphyrins.
Step-by-step explanation:
The condition characterized by extreme photosensitivity, reddish-brown urine, and splenomegaly is likely to be Erythropoietic Protoporphyria (EPP). This is a form of porphyria which affects the bone marrow, and it presents with symptoms such as sensitivity to light leading to painful skin conditions and may also lead to reddish-brown discoloration of the urine due to the presence of porphyrins. Porphyrias are a group of diseases caused by defects in heme production, leading to a buildup of porphyrins, which are heme precursors.
Chronic idiopathic jaundice is marked by excessive excretion of bile pigments, including type-I coproporphyrins, rather than the type-II usually found in urine. This disorder is inherited in an autosomal recessive pattern. Nevertheless, the symptoms presented in the question most closely match those of EPP rather than chronic idiopathic jaundice.