for solely nursing infants of black mothers, in winter in temperate climates, suffering poor nutrition and no vitamin d supplementation. people with darker skin produce less vitamin d than those with lighter skin, for the same amount of sunlight. treatment diet and sunlight cholecalciferol (d3) ergocalciferol (d2) treatment involves increasing dietary intake of calcium, phosphates and vitamin d. exposure to ultraviolet b light (most easily obtained when the sun is highest in the sky), cod liver oil, halibut-liver oil, and viosterol are all sources of vitamin d. a sufficient amount of ultraviolet b light in sunlight each day and adequate supplies of calcium and phosphorus in the diet can prevent rickets. darker-skinned people need to be exposed longer to the ultraviolet rays. the replacement of vitamin d has been proven to correct rickets using these methods of ultraviolet light therapy and medicine. recommendations are for 400 international units (iu) of vitamin d a day for infants and children. children who do not get adequate amounts of vitamin d are at increased risk of rickets. vitamin d is essential for allowing the body to uptake calcium for use in proper bone calcification and maintenance. supplementation sufficient vitamin d levels can also be achieved through dietary supplementation and/or exposure to sunlight. vitamin d3 (cholecalciferol) is the preferred form since it is more readily absorbed than vitamin d2. most dermatologists recommend vitamin d supplementation as an alternative to unprotected ultraviolet exposure due to the increased risk of skin cancer associated with sun exposure. endogenous production with full body exposure to sunlight is approximately 250 µg (10,000 iu) per day. according to the american academy of pediatrics (aap), all infants, including those who are exclusively breast-fed, may need vitamin d supplementation until they start drinking at least 17 us fluid ounces (500 ml) of vitamin d-fortified milk or formula a day. despite this recommendation, a recent cochrane systematic review has found limited evidence that vitamin d plus calcium, or calcium alone compared to vitamin d improves healing in children with nutritional rickets. surgery occasionally surgery is needed to correct severe and persistent deformities of the lower limbs, especially around the knees namely genu varum and genu valgum. surgical correction of rachitic deformities can be achieved through osteotomies or guided growth surgery. guided growth surgery has almost replaced the use of corrective osteotomies. the functional results of guided growth surgery in children with rickets are satisfactory. while bone osteotomies work through acute/immediate correction of the limb deformity, guided growth works through gradual correction. epidemiology in developed countries, rickets is a rare disease (incidence of less than 1 in 200,000). recently, cases of rickets have been reported among children who are not fed enough vitamin d. in 2013/2014 there were fewer than 700 cases in england. in 2019 the number of cases hospitalised was said to be the highest in 50 years. rickets occurs relatively commonly in the middle east, africa, and asia. history skeleton of infant with rickets, 1881 greek physician soranus of ephesus, one of the chief representatives of the methodic school of medicine who practiced in alexandria and subsequently in rome, reported deformation of the bones in infants as early as the first and second centuries ad. rickets was not defined as a specific medical condition until 1645, when an english physician daniel whistler gave the earliest known description of the disease. in 1650 a treatise on rickets was published by francis glisson, a physician at caius college, cambridge, who said it had first appeared about 30 years previously in the counties of dorset and somerset. in 1857, john snow suggested rickets, then widespread in britain, was being caused by the adulteration of bakers' bread with alum. german pediatrician kurt huldschinsky successfully demonstrated in the winter of 1918–1919 how rickets could be treated with ultraviolet lamps. the role of diet in the development of rickets was determined by edward mellanby between 1918 and 1920. in 1923, american physician harry steenbock demonstrated that irradiation by ultraviolet light increased the vitamin d content of foods and other organic materials. steenbock's irradiation technique was used for foodstuffs, but most memorably for milk. by 1945, rickets had all but been eliminated in the united states. etymology the word rickets may be from the old english word wrickken ('to twist'), although because this is conjectured, several major dictionaries simply say "origin unknown". the name rickets is plural in form but usually singular in construction. the greek word rachitis (ῥαχίτης, meaning 'in or of the spine') was later adopted as the scientific term for rickets, due chiefly to the words' similarity in sound. vide: aubrey's brief lives: the word has no connection whatever with the greek rachitis. i quote: " about 1620 one ricketts of newberye a practictioner of physick was excellent at the curing children with swoln heads, and small legges: and the disease being new, and without a name, he being so famous for the cure of it, they called the disease the ricketts: as the king's evill from the king's cureing of it with his touch; and now 'tis good sport to see how they vex their lexicons, and fetch it from the greek paxis, the back bone."