Vitamin D deficiency rickets

Key words: Myopathy, Vitamin D deficiency, Rickets

Mouhamed, a 7-year-old boy of African origin, presented with progressive fatigue and difficulty in walking. He was never treated with vitamin D supplementation. The evaluation of his calcium-phosphorus metabolism revealed a myopathy related to severe rickets. Therefore, he was treated with high-dose vitamin D3 and myopathy and fatigue progressively resolved. Vitamin D plays a crucial role in the calcium-phosphorus metabolism, by acting on enterocytes, osteoclasts and renal tubule. Vitamin D deficiency is defined when the 25OHD value is less than 20 ng/ml. In order to guarantee the assumption of the minimum daily dose of vitamin D, it is recommended to start vitamin D3 supplementation in all newborns and infants in their first year of life, regardless of the feeding modality. Exposure to the sun is essential for the activation of vitamin D, so dark-skinned children and mothers or those little exposed to the sun should start vitamin D3 supplementation. Vitamin D3 should also be supplemented in children with cerebral palsy and in patients treated with anti-epileptic drugs. Other conditions at risk of vitamin D deficiency are inflammatory bowel disease, celiac disease, cystic fibrosis, obesity, liver failure, cholestasis and vegetarian or vegan diets. Classic signs of rickets are the rickety rosary, the widening of the wrist and the arching of the tibia. Severe hypocalcaemia secondary to vitamin D deficiency can occur with dilated cardiomyopathy or convulsions, especially in dark-skinned infants. Vitamin D deficiency should be considered in children with progressive myopathy or muscular weakness, especially in dark-skinned ones or in those poorly exposed to the sun for cultural or religious reasons.