A patient who inherits a mutation in CYP24A1 may develop a mild idiopathic hypercalcemia during infancy, typically triggered when vitamin D is given to prevent rickets.


Protein affected: CYP24A1 (25-hydroxyvitamin D 24 hydroxylase)

Chromosome: 20q13


A mutation in CYP24A1 results increased levels of 1,25-dihydroxyvitamin D3 secondary to decreased degradation.


Clinical features triggered by vitamin D administration:

(1) failure to thrive

(2) vomiting

(3) anorexia

(4) dehydration

(5) muscle hypotonia

(6) nephrocalcinosis

(7) hypercalcemia


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