Muscle pain and mild proximal weakness can be due to vitamin D deficiency

Objective: Vitamin D is essential in bone and muscle health. Vitamin D deficiency is a global health problem and diagnosis should not be missed, especially with the increasing migration of children from less developed countries with insufficient vitamin D prophylaxis. Severe vitamin D deficiency typically causes rickets in children, but may also present with myalgia and muscle weakness. Vitamin D deficiency must be considered in the differential diagnosis of myopathic disease. Case report: We report six female patients who were finally diagnosed with severe vitamin D deficiency induced myopathy. First symptoms were muscle pain, especially of lower extremities, increasing on exertion at the age of 4–16 years. Clinical findings included mild proximal muscle weakness and gait abnormalities with difficulties running and climbing stairs. Three patients underwent extended negative diagnostic investigations for a neuromuscular disorder. 25- hydroxy vitamin D levels were markedly decreased in all patients, in three patients Creatine kinase was mildly elevated in addition. One patient fullfilled criteria for rickets in addition, in one secondary hyperparathyroidism was present. With the diagnosis of severe vitamin D deficiency all patients were treated with high doses of Vitamin D. Initial symptoms improved rapidly after a few weeks of treatment and clinical findings were completely reversible. 25- hydroxy vitamin D levels returned to normal values or increased markedly with treatment. All patients are still supplemented with vitamin D. Conclusion: Vitamin D deficiency can present with significant muscle impairment, mimicing neuromuscular disease. In the differential diagnosis of myopathies, vitamin D deficiency must be taken into consideration. Diagnosis and treatment are simple, and extensive investigations might be avoided.