In 1936 we reported a case of hypothyroidism1 in a child in which one of the outstanding features was that of cardiac enlargement. This enlargement was reduced with thyroid therapy, but the heart returned to its original size when use of the medicament was discontinued. In that report we discussed the diagnostic features of "myxedema heart" and included a differential diagnosis of some of the less commonly appreciated causes of cardiac enlargement in childhood.
Since our report we have been unable to find recorded in the literature further cases of this condition in children. The latest edition of the textbook of Holt and McIntosh.2 in a discussion of myxedema heart, contains this statement: "With this obscure condition we have had no experience." In neither Griffith and Mitchell's3 textbook nor in Brennemann's4 "Practice of Pediatrics" is there mention of electrocardiographic or other cardiac findings in their discussions
BARATZ JJ, BRONSTEIN IP. THE HEART IN CHILDREN WITH THYROID DEFICIENCY. Am J Dis Child. 1942;64(3):471-474. doi:10.1001/archpedi.1942.02010090073007