In 2016 the U.S. Bishop's Conference (USCCB) updated its article "Celiac Disease, Alcohol Intolerance, and the Church's Pastoral Response."
Celiac disease is an immune reaction to eating gluten, a protein found in wheat, barley and rye. For those with the disease, eating gluten triggers an immune response in the small intestine. In 2012, it was estimated 1.8 million Americans have celiac disease, but 1.4 million are unaware they have it. The lay faithful who are not able to receive Holy Communion at all under the species of bread, even of low-gluten hosts, may receive Holy Communion under the species of wine only. Mustum is defined as grape juice in which fermentation has begun, but has been suspended with the result that its alcohol content (usually less than 1.0%) does not reach the levels found in most table wines.
As is noted in this document, it is within the competence of the diocesan Bishop to permit priests, deacons or the laity to use low-gluten hosts or mustum for the celebration of the Eucharist. Bishop Brungardt hereby delegates this authority to priests to allow members of the lay faithful to use low-gluten hosts or mustum habitually for as long as the situation warrants.
The last page of the article provides information where to obtain low-gluten hosts and mustum.
Bishops recently received from the Congregation for Divine Worship and the Sacraments a "Circular Letter on the Bread and Wine for the Eucharist." This document offers a reminder of the valid matter that is required for the bread and wine used in the celebration of the Eucharist.
Also recently, Bishop Brungardt provided to priests links to reputable Catholic suppliers of altar wines.