Primary Care Update: Celiac Disease: Could You Be Missing This Common Problem?

Until recently, celiac diseasewas considered a rare disorder.However, new evidencesuggests that about1% of Americans are affected.As serologic tests that detect autoantigensinvolved in celiac diseasebecome more widely used, morecases will likely be identified.¹
In response to these recentdevelopments, the NIH convened aconference on celiac disease earlierthis year. The highlights are presentedhere.
A QUICK OVERVIEW
Symptoms of celiac diseaseoccur when gluten--a dietary proteinpresent in wheat, barley, andrye--is ingested. In persons whohave celiac disease, gluten activatesan abnormal mucosal immune response,which damages the smallintestine by inducing chronic inflammationof the mucosa. Untreated,celiac disease can cause atrophy ofthe intestinal villi, vitamin and mineraldeficiencies, osteoporosis, andother extraintestinal problems.
MAKING THE DIAGNOSISClinical features. The clinicalmanifestations of celiac disease aremyriad. Although primarily a disorderof the GI tract, celiac disease isa multisystem disorder and it commonlypresents with many non-GIrelatedsymptoms--or it may evenbe completely asymptomatic.
GI symptoms of celiac diseaseinclude diarrhea; weight loss; vomiting;abdominal pain, bloating, anddistention; anorexia; and constipation.The presence of obesity doesnot preclude a diagnosis. A commonextraintestinal symptom is dermatitisherpetiformis, an intensely pruriticrash on the extensor surfaces of theextremities. Other non-GI symptomsinclude iron deficiency anemia, failureto grow, short stature, delayedpuberty, recurrent fetal loss, osteoporosis,vitamin deficiencies, fatigue,protein-calorie malnutrition, recurrentaphthous stomatitis, elevatedtransaminase levels, and dentalenamel hypoplasia. Celiac diseaseis sometimes associated with autoimmuneendocrinologic disorders, suchas thyroiditis. Also, several neuropsychiatricconditions have been reportedin persons with celiac disease,such as depression, anxiety, peripheralneuropathy, ataxia, epilepsy withor without cerebral calcifications, andmigraine headaches.
The Table lists the putative subphenotypesof celiac disease. Complicationsare generally only observedin adults, after many years of havingthe disease.
Diagnostic tests. There is noone test that can definitively diagnoseceliac disease; instead, a continuumof a combination of laboratoryand histopathological results maylead to diagnosis or exclusion of thedisorder.
All diagnostic tests must beperformed while the patient is ona gluten-containing diet. If you suspectceliac disease, the first step isto order serologic testing. Becauseof their high sensitivities and specificities,the recommended studiesare IgA antihuman tissue transglutaminase(TTG) and IgA endomysialantibody immunofluorescence(EMA), which both have an equallyhigh level of diagnostic accuracy.
Multiple biopsies of the smallbowel obtained from the second duodenumor beyond are recommendedfor patients who have a positiveceliac disease antibody test. Multiplebiopsies are recommended becausehistologic changes may be focal. Abiopsy is not necessary in those patientswho have proven dermatitisherpetiformis.

The pathology report shouldspecify the degree of crypt hyperplasiaand villous atrophy as wellas assess the number of intraepitheliallymphocytes (

Figure

). Somedegree of villous atrophy is considerednecessary to make a diagnosisof celiac disease; the finding of intraepitheliallymphocytes with crypthyperplasia without villous bluntingis much less definitive. Endoscopicevaluation without a biopsy cannotconfirm or exclude a diagnosis,since endoscopic findings are notsufficiently sensitive for celiac disease.A presumptive diagnosis ofceliac disease can be made withboth positive serology results andbiopsy results. A definitive diagnosisof celiac disease is confirmedwhen the patient's symptoms subsequentlyresolve on a gluten-freediet.
If a patient has symptoms suggestiveof celiac disease, but hasnegative findings on serologic testing,there are generally 3 possiblescenarios:

• The patient has a selective IgA deficiency,and an IgG-TTG or IgGEMAtest should be performed.
• The serologic test results could bea false-negative--in which case thetest can be repeated, or a differentserologic test could be performed.
• The patient may not have celiacdisease.

When the diagnosis is uncertainbecause of intermediate testresults, testing for certain geneticmarkers can be useful. Ninety-sevenpercent of persons who have celiacdisease have a DQ2 or DQ8 HLAhaplotype genetic marker, comparedwith 40% of the general population.Thus, the absence of these2 genetic markers has a high negativepredictive value for celiacdisease.

WHOM TO TEST

Patients with symptoms.

Testpersons who have characteristicGI symptoms, including chronic diarrhea,malabsorption, weight loss,and abdominal distention. However,since celiac disease is a multisystemdisorder, it is important to keepnon-GI-presenting symptoms inmind. Consider testing patientswithout alternate explanations forconditions such as persistent transaminaseelevations, short stature,delayed puberty, iron deficiencyanemia, recurrent fetal loss, infertility,irritable bowel syndrome, persistentaphthous stomatitis, autoimmunediseases, peripheral neuropathy,cerebellar ataxia, and dentalenamel hypoplasia.

Persons at risk for celiacdisease.

These include persons withtype 1 diabetes mellitus or other autoimmuneendocrinopathies, Downsyndrome, and Turner syndromeand first- and second-degree relativesof those with celiac disease. Routinescreening is not recommended becausecurrent data do not show aclear outcome benefit. However, ifone of your patients has any of thesesyndromes, and presents with atleast one symptom of celiac disease,testing is recommended.

TREATMENT

Start treatment of celiac diseaseonly after the diagnostic evaluation,including serology and biopsy, hasbeen completed. To successfully manage celiac disease the patientmust adhere to a gluten-free diet forlife. Such a diet excludes wheat, rye,and barley because these grainscontain the peptides or glutens thatare known to cause celiac disease.Even small quantities of gluten maybe harmful to the patient. Note thatalthough oats are technically glutenfree,they are often contaminatedwith small amounts of gluten.
The following anagram demonstratesthe key elements in themanagement of patients with celiacdisease:

• Consultation with a skilled dietitian.
• Education about the disease.
• Lifelong adherence to a gluten-freediet.
• Identification and treatment ofnutritional deficiencies.
• Access to an advocacy group.
• Continuous long-term follow-up bya multidisciplinary team.

Patient education about celiacdisease and about how to identifygluten-containing products is associatedwith improved self-management.Encourage your patients toparticipate in a celiac disease advocacygroup, because it can be aneffective means of adhering to agluten-free diet and can also provideemotional and social support.
Celiac disease is often associatedwith deficiencies in iron, calcium,phosphorus, folate, vitamin B

₁₂

,and fat-soluble vitamins. Considersupplementation if necessary. Personswith celiac disease should bescreened for osteoporosis since theprevalence of osteoporosis is highamong those with celiac disease.
A team-based approach to managingceliac disease is important. Inaddition to treatment by a physicianand participation in a support group,patients with celiac disease shouldmeet with a dietitian to plan a nutritionallybalanced gluten-free diet.
Regular follow-up is essential sothat you can assess symptoms andmonitor for complications. In children,this also includes monitoringtheir growth and development.
Stress to your patients the necessityof maintaining a strict gluten-freediet for life.