Greetings from someone who happens to be gluten intolerant...
Folks with celiac disease (CD) and dermatitis herpetiformis (DH) have autoimmune disorders which regard the gluten found in wheat, rye, and barley as a toxin and respond by damaging the villi in the small intestine (in CD patients) and/or causing ferociously itchy skin rashes (in DH patients). Estimates vary, but the incidence of gluten intolerance in the general population may be as significant as 1 person in 100. Many CD and DH patients go misdiagnosed. Those of us who are gluten intolerant must avoid all products which contain wheat, rye, and barley. Most celiacs avoid oats and spelt, as well. Among the biggest dietary challenges for CD and DH patients is avoiding hidden gluten in apparently innocuous products (such as "modified food starch" or "hydrolyzed vegetable protein" or "natural flavoring" or "malt vinegar") and avoiding foods which may have been cross-contaminated by coming in contact with gluten-containing foods.
Gluten-free pastas (and cookies, breads, crackers, etc.) are readily available in quite a few health food stores, as well as in many supermarkets. I've had a few GF pastas made from rice flour and rice/corn flour blends, and well... I prefer other substitutes, like spaghetti squash instead of spaghetti, or eggplant lasagna. Extra care must be taken when preparing many GF pastas as they tend to be easy to overcook and fall apart. While I've found some of the rice pastas OK for oriental food applications, they tend to be mediocre at best when used for Italian food entrees. That's just my opinion; your mileage may vary.
General purpose gluten free flours are often made with a blend of white and brown rice flours, potato starch, tapioca flour, xanthan and/or guar gums (to provide some "stickiness," which the gluten in wheat does). The ratio of ingredients are often varied depending on the end product.
Regards,
mrmufin