We thank Drs Silverman and Shinder for raising interesting discussion points regarding our case series.

The radiology images were reviewed by pediatric radiologists, compared to established norms for extraocular muscles, or compared to the contralateral eye in unilateral cases, before diagnosing muscle enlargement. A sagittal section was included in a patient to demonstrate the thickness of the muscle belly along the length of the muscle.

The tests mentioned in the letter may be of use in future cases. Previous case reports of IgG4-related sclerosing disease involving extraocular muscles have all involved other adnexal structures, and most have been in adults or with other systemic autoimmune conditions. In regard to other systemic work-up, several patients underwent investigations for the common conditions reported in the literature for enlarged muscles in this age group, and all underwent thyroid function tests. The patients did not undergo the extra investigations suggested in the letter; however, these patients did not demonstrate any signs or symptoms of other disease processes over several months to years of follow-up.

The biopsies were performed in the areas of muscle enlargement demonstrated by the radiology. The small specimen mentioned in the letter refers to a biopsy performed 20 years ago in a patient whose muscle contour otherwise remained stable, and who did not demonstrate any other disease process during the long follow-up period. A larger specimen may be useful for the additional tests available currently.