Rickets – A preventable skeletal disorder
Rickets is a preventable skeletal disorder that affects infants and young children, causing soft and weakened bones. We spoke to Dr Tony Huynh, a paediatric endocrinologist at the Queensland Children’s Hospital and Chemical Pathologist at Mater Pathology in Brisbane, to find out more about this treatable disease and to discuss the role of pathology in the diagnosis, management and treatment.
“In paediatric terms, rickets is a disorder of defective chondrocyte differentiation and mineralization of the growth plate and defective osteoid mineralization. The adult equivalent is called osteomalacia, which is softening of the bones.
“There are genetic disorders of vitamin D and phosphate metabolism that cause rickets but these are relatively rare, and the vast majority of cases have a nutritional cause. Vitamin D deficiency and/or low calcium would be the predominant cause, which we refer to as nutritional rickets. An estimated incidence of vitamin D deficiency, from a 2012 paper published in the Medical Journal of Australia that defined a deficiency as 25(OH)-vitamin D levels <50 nanomoles per litre (nmol/L), was 4.9/100,000/year in Australian children less than 16 years of age. The majority of these cases had X-ray changes.”
Most vitamin D is synthesised in the skin after exposure to ultraviolet B rays from direct sunlight, with dietary sources contributing little. Vitamin D deficiency and associated rickets are re-emerging as major public health issues worldwide, including in Australia.
“The definition of vitamin D deficiency has been the subject of debate in recent years. A global consensus came out in 2016 on nutritional rickets. It defines “deficiency” as less than <30 nmol/L, “insufficiency” as 30-50 nmol/L and “sufficient” as >50 nmol/L in children and adolescents. It is important that clinicians are aware that there are global consensus guidelines.”
Rickets is most common in infants and young children. During this time, they usually experience rapid growth, meaning their bodies need high levels of calcium and phosphate in order for their bones to develop.
“Healthy children shouldn’t be screened routinely because they are not at particular/much risk. The main risk groups are children in refugee populations/groups who may be dark-skinned, or people who are covered up, for example the Muslim population – that’s probably the biggest group that we see with vitamin D deficiency rickets. The other risk group is infants that have been exclusively breast fed, because breast milk is low in vitamin D. Those with malabsorption form another risk group. Pancreatic insufficiency, for example, is an inability to absorb fat-soluble vitamins.”
“Rickets can be asymptomatic. However, clinical symptoms include: bony features; swelling of the wrists and ankles; delayed fontanelle closing, which is normally closed by 2 years of age; and delayed tooth eruptions. The classic signs are leg deformities such as bowed legs, called genu valgum; and rachicitic rosary, which is widening of costochondral joints. You may also see frontal bossing, the term for a protruding forehead; and bone pain.” “There are classical X-ray signs such as splaying or fraying of the metaphyses, widening of growth plates, and osteopenia”. “There may be associated minimal trauma fractures”. “Hypocalcaemia can also occur.”
“Rickets is quite treatable. Obviously if it is really severe with hypocalcaemia then calcium needs to be replaced, sometimes intravenously. Rickets is really about getting enough vitamin D and calcium through daily safe sun exposure, and by eating foods that contain vitamin d and calcium such as fish, liver, milk, and eggs. In Australia we tend to use vitamin D3 or cholecalciferol as supplements, along with calcium supplements. There are minimum requirements at different ages, and the 2016 guideline goes through some of these. Even with significant deformities, such as leg bowing, once you correct the vitamin D deficiency and the calcium levels there tends to be a good recovery.
“I think the important public message is that if your child is healthy then there is a pretty low risk of rickets. From a breast-feeding perspective, we aren’t saying don’t exclusively breastfeed but there is the possibility that you may need to supplement your child with vitamin D during that time.” Screening of at risk populations is appropriate.
To view the global consensus statement on rickets, please visit:
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This article appeared in the February 2019 Edition of ePathWay which is an online magazine produced by the Royal College of Pathologists of Australasia (http://www.rcpa.edu.au/Library/Publications/ePathway).
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