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Nutritional rickets: when should you consider a differential diagnosis?

Rickets is a common condition in childhood, caused by deficiency of calcium, phosphorous and/or vitamin D.1 Defective bone mineralisation leads to abnormalities of growth plate cartilage, predominantly in long bones,1 causing symptoms that can include bone pain, bowing of the lower limbs and an abnormal gait, fragile bones, delayed growth and dental problems.2 Hypophosphataemia is the underlying mechanism of all forms of rickets; it results in reduced apoptosis of hypertrophic cells of the growth plate, causing them to accumulate, and reduced mineralisation of primary spongiosa in the metaphysis (new bone).1,3

Rickets can be acquired (nutritional) or inherited. Nutritional rickets is the most common form and is caused, in most cases, by a dietary deficiency of vitamin D or, more rarely, calcium or phosphorus.4 Inherited rickets can be vitamin D dependent, where hyposphosphataemia occurs as a result of defective absorption of dietary phosphate and calcium, and resulting secondary hyperparathyroidism,5 or vitamin D independent (ie not caused by a defect of vitamin D intake, secretion or action), where phosphate deficiency is the primary defect.1,6

X-linked hypophosphataemia (XLH) is the most common cause of heritable rickets, with an incidence of 1 in 20,000 live births, and occurs due to inactivating mutations in PHEX.1 XLH is often misdiagnosed as nutritional rickets, with which it shares many symptoms and biochemical findings. Correct and timely diagnosis of XLH is important however, as early initiation of treatment can result in improved outcomes.7

This module contains a series of 10 multiple choice questions, designed to get you thinking about the differential diagnoses of nutritional rickets, followed by a short video telling the story of a real-life patient with XLH.

Learning objectives

  1. Improve awareness of red flag signals which could indicate an incorrect diagnosis of nutritional rickets
  2. Improve understanding of alternative diagnoses that could be considered when a patient does not respond to standard care for nutritional rickets
  3. Increase understanding of XLH as a condition
  4. Increase understanding of appropriate testing to confirm a diagnosis of XLH
Start the module ›

EACCME Accreditation

Nutritional rickets: when should you consider a differential diagnosis?, made available on https://sponsored.m3medical.com/kyowa-kirin/ and organized by M3 (EU) Limited, is accredited by the European Accreditation Council for Continuing Medical Education (EACCME) to provide the following CME activity for medical specialists.
Each medical specialist should claim only those credits that he/she actually spent in the educational activity. The EACCME is an institution of the European Union of Medical Specialists (UEMS). Only those e-learning materials that are displayed on the UEMS-EACCME website have formally been accredited.
Through an agreement between the European Union of Medical Specialists (UEMS) and the American Medical Association (AMA), physicians may convert EACCME credits to an equivalent number of AMA PRA Category 1 CreditsTM. Information on the process to convert EACCME credit to AMA credit can be found at https://www.ama-assn.org/.

References

  1. Jagtap V S, Sarathi V et al. Hypophosphatemic rickets. Indian J Endocrinol Metab 2012;16(2):177-182
  2. NHS. Rickets and osteomalacia. Available at: www.nhs.uk. Accessed October 2020
  3. Uday S, Hogler W. Nutritional rickets and osteomalacia in the twenty-first century: revised concepts, public health, and prevention strategies. Curr Osteoporos Rep 2017;15(4):293-302
  4. Chibuzor M T, Graham-Kalio D et al. Vitamin D, calcium or a combination of vitamin D and calcium for the treatment of nutritional rickets in children. Cochrane Database Syst Rev 2020;4:CD012581
  5. Genetics Home Reference. Vitamin D-dependent rickets. Available at: ghr.nlm.nih.gov. Accessed October 2020
  6. Patel-Bhakta H G, Campbell P R. Dental management of patients with rickets. Available at: dimensionsofdentalhygiene.com. Accessed October 2020
  7. Carpenter T O, Imel E A et al. A clinician's guide to X-linked hypophosphatemia. J Bone Miner Res 2011;26(7):1381-1388
  8. Haffner D, Emma F et al. Clinical practice recommendations for the diagnosis and management of X-linked hypophosphataemia. Nat Rev Nephrol 2019;15(7):435-455
  9. Genetic and Rare Diseases Information Centre (GARD). X-linked hypophosphatemia. Available at: rarediseases.info.nih.gov. Accessed October 2020
  10. Thacher T D, Fischer P R et al. Radiographic scoring method for the assessment of the severity of nutritional rickets. J Trop Pediatr 2000;46(3):132-139

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