Rickets

Rickets, is a condition that results in weak or soft bones in children and may have either dietary-deficiency or genetic causes. Symptoms include bowed legs, stunted growth, bone pain, large forehead, and trouble sleeping. Complications may include bone deformities, bone pseudofractures and fractures, muscle spasms, or an abnormally curved spine. The analogous condition in adults is osteomalacia.
One can characterise a child who appears to suffer from rickets as rachitic.
The most common cause of rickets is a vitamin-D deficiency, although hereditary genetic forms also exist. The condition can result from eating a diet without enough vitamin D, dark skin, too little sun exposure, exclusive breastfeeding without vitamin D supplementation, celiac disease, and certain genetic conditions. Other factors may include not enough calcium or phosphorus. The underlying mechanism involves insufficient calcification of the growth plate. Diagnosis is generally based on blood tests finding a low calcium, low phosphorus, and a high alkaline phosphatase together with X-rays.
Prevention for exclusively breastfed babies is vitamin D supplements. Otherwise, treatment depends on the underlying cause. If due to a lack of vitamin D, treatment is usually with vitamin D and calcium. This generally results in improvements within a few weeks. Bone deformities may also improve over time. Occasionally, surgery may be performed to correct bone deformities. Genetic forms of the disease typically require specialized treatment.
Rickets occurs relatively commonly in the Middle East, Africa, and Asia. It is generally uncommon in the United States and Europe, except among certain minority groups, but rates have been increasing among some populations. It begins in childhood, typically between the ages of 3 and 18 months of age. Rates of disease are equal in males and females. Cases of what is believed to have been rickets have been described since the 1st century AD, and the condition was widespread in the Roman Empire. The disease occurred commonly into the 20th century. Early treatments included the use of cod liver oil.

Signs and symptoms

Signs and symptoms of dietary deficiency rickets can include bone tenderness, and a susceptibility for bone fractures, particularly greenstick fractures. Early skeletal deformities can arise in infants such as soft, thinned skull bones – a condition known as craniotabes, which is the first sign of rickets; skull bossing may be present and a delayed closure of the fontanelles.
Young children may have bowed legs and thickened ankles and wrists; older children may have knock knees. Spinal curvatures of kyphoscoliosis or lumbar lordosis may be present. The pelvic bones may be deformed. A condition known as rachitic rosary can result from the thickening caused by nodules forming on the costochondral joints. This appears as a visible bump in the middle of each rib in a line on each side of the body. This somewhat resembles a rosary, giving rise to its name. The deformity of a pigeon chest may result in the presence of Harrison's groove.
Hypocalcemia, a low level of calcium in the blood, can result in tetany – uncontrolled muscle spasms. Dental problems can also arise.
An X-ray or radiograph of an advanced patient with rickets tends to present in a classic way: the bowed legs and a deformed chest. Changes in the skull also occur, causing a distinctive "square-headed" appearance known as "caput quadratum". These deformities persist into adult life if not treated. Long-term consequences include permanent curvatures or disfiguration of the long bones, and a curved back.

Cause

Maternal deficiencies may be the cause of overt bone disease from before birth and impairment of bone quality after birth. The primary cause of congenital rickets is vitamin D deficiency in the mother's blood. Vitamin D ensures that serum phosphate and calcium levels are sufficient to facilitate the mineralization of bone. Congenital rickets may also be caused by other maternal diseases, including severe osteomalacia, untreated celiac disease, malabsorption, pre-eclampsia, and premature birth. Rickets in children is similar to osteomalacia in adults, and differs from osteoporosis, where there is increased porosity of bone leading to brittleness.. Prenatal care includes checking vitamin levels and ensuring that any deficiencies are supplemented.
Exclusively breast-fed infants may require rickets prevention by vitamin D supplementation or increased exposure to sunlight.
In sunny countries such as Nigeria, South Africa, and Bangladesh, there is sufficient endogenous vitamin D due to exposure to the sun. However, the disease occurs among older toddlers and children in these countries, which in these circumstances is attributed to low dietary calcium intakes due to a mainly cereal-based diet.
Those at higher risk for developing rickets include:

Breast-fed infants whose mothers are not exposed to sunlight
Breast-fed infants who are not exposed to sunlight
Breast-fed babies who are exposed to little sunlight
Adolescents, in particular when undergoing the pubertal growth spurt
Any child whose diet does not contain enough vitamin D or calcium

Diseases causing soft bones in infants, like hypophosphatasia or hypophosphatemia, can also lead to rickets.
Strontium is allied with calcium uptake into bones; at excessive dietary levels, strontium has a rachitogenic action.

Sunlight

Sunlight, especially ultraviolet light, lets human skin cells convert vitamin D from an inactive to an active state. In the absence of vitamin D, dietary calcium is not properly absorbed, resulting in hypocalcaemia, leading to skeletal and dental deformities and neuromuscular symptoms, e.g., hyperexcitability. Foods that contain vitamin D include butter, eggs, fish liver oils, margarine, fortified milk and juice, portabella and shiitake mushrooms, and oily fishes such as tuna, herring, and salmon. A rare X-linked dominant form exists called vitamin D-resistant rickets or X-linked hypophosphatemia.
Cases have been reported in Britain in recent years of rickets in children of many social backgrounds caused by insufficient production in the body of vitamin D because the sun's ultraviolet light was not reaching the skin due to use of strong sunblock, too much "covering up" in sunlight, or not getting out into the sun. Other cases have been reported among the children of some ethnic groups in which mothers avoid exposure to the sun for religious or cultural reasons, leading to a maternal shortage of vitamin D, and people with darker skin need more sunlight to maintain vitamin D levels.
Rickets had historically been a problem in London, especially during the Industrial Revolution. Persistent thick fog and heavy industrial smog permeating the city blocked out significant amounts of sunlight to such an extent that up to 80 percent of children had varying degrees of rickets. It is sometimes known "the English Disease" in some foreign languages.

Skin color theory

Rickets is often a result of vitamin D3 deficiency. The correlation between human skin color and latitude is thought to be the result of positive selection to varying levels of solar ultraviolet radiation. Northern latitudes have selection for lighter skin that allows UV rays to produce vitamin D from 7-dehydrocholesterol. Conversely, latitudes near the equator have selection for darker skin that can block the majority of UV radiation to protect from toxic levels of vitamin D, as well as skin cancer.
An anecdote often cited to support this hypothesis is that Arctic populations whose skin is relatively darker for their latitude, such as the Inuit, have a diet that is historically rich in vitamin D. Since these people acquire vitamin D through their diet, there is no positive selective force to synthesize vitamin D from sunlight.
Environment mismatch: Vitamin D deficiency arises from a mismatch between an individual's previous and current environment. This risk of mismatch increases with advances in transportation methods and increases in urban population size at high latitudes.
Similar to the environmental mismatch when dark-skinned people live at high latitudes, Rickets can also occur in religious communities that require long garments with hoods and veils. These hoods and veils act as sunlight barriers that prevent individuals from synthesizing vitamin D naturally from the sun.
In a study by Mithal et al., vitamin D insufficiency of various countries was measured by lower 25-hydroxyvitamin D. 25 D is an indicator of vitamin D insufficiency that can be easily measured. These percentages should be regarded as relative vitamin D levels, and not as predictive evidence for the development of rickets.
Asian immigrants living in Europe have an increased risk of vitamin D deficiency. Vitamin D insufficiency was found in 40% of non-Western immigrants in the Netherlands, and in more than 80% of Turkish and Moroccan immigrants.
The Middle East, despite high rates of sun-exposure, has the highest rates of rickets worldwide. This fact can be explained by limited sun exposure due to cultural practices and lack of vitamin D supplementation for breast-feeding women. Up to 70% and 80% of adolescent girls in Iran and Saudi Arabia, respectively, have vitamin D insufficiency. Socioeconomic factors that limit a vitamin D-rich diet also play a role.
In the United States, vitamin D insufficiency varies dramatically by ethnicity. Among females aged 70 years and older, the prevalence of low serum 25 D levels was 28.5% for non-Hispanic whites, 55% for Mexican Americans, and 68% for non-Hispanic blacks. Among males, the prevalence was 23%, 45%, and 58%, respectively.
A systematic review published in the Cochrane Library looked at children up to three years old in Turkey and China and found a beneficial association between vitamin D and rickets. In Turkey, children who received vitamin D had only a 4% chance of developing rickets compared to children who received no medical intervention. In China, a combination of vitamin D, calcium, and nutritional counseling was linked to a decreased risk of rickets.
Parents can supplement their nutritional intake with vitamin D enhanced beverages if they feel their child is at risk for vitamin D deficiency.
A 2019 review linked rickets disease to exclusive consumption of Neocate baby formula.