Rickets
Rickets is the softening/weakening of bones in children (rickets in adults is called osteomalacia), primarily due to a vitamin D deficiency. Vitamin D facilitates the absorption of calcium and phosphorous in the small intestine, so a deficiency in this vitamin inhibits the bones from maintaining proper mineral levels. Signs and symptoms are: distended abdomen (due to liver/spleen enlargement), bone fragility, abnormal curvature of long bones, protruding forehead, growth retardation, and kyphosis (hunchback). Treatment options include vitamins/dietary supplements and orthopedic surgery to correct abnormal curvature of the long bones.
The liver/spleen enlargement is not present in ALL cases of rickets. It can be seen where rickets is a secondary disease due to an underlying liver problem (the liver produces a type of vitamin D called calcidiol, so when liver function is impaired it can lead to vitamin D deficiency and ultimately rickets). Where rickets is not a secondary disease, abdominal muscle weakness causes a protruding abdomen, where the liver and spleen are palpable, but not necessarily enlarged.