PTH and rickets: Severe hypocalcemia and the history of recent vitamin supplementation withdrawal led to the clinical suspicion of rickets, therefore we requested a complete assessment of phospho-calcium metabolism which showed significant deficiency of 25-hydroxyvitamin D (25-OH D) [less than 4 ng/ml (normal values: 20–50 ng/ml)] with increased PTH [254 pg/ml (normal values: 6.5–36.8 pg/ml)].