Individuals reporting idiopathic malodor production: demographics and incidence of trimethylaminuria

Am J Med. 2011 Nov;124(11):1058-63. doi: 10.1016/j.amjmed.2011.05.030. Epub 2011 Aug 16.


Background: Individuals with the metabolic disorder trimethylaminuria may sporadically produce malodors despite good hygiene. The psychosocial impact of trimethylaminuria can be considerable. However, trimethylaminuria is difficult to diagnose without specialized tests, in part because odor production is diet-dependent, and malodors may not be present during medical examinations. Thus, the prevalence and demographics of trimethylaminuria remain unclear.

Methods: We tested 353 patients who had unexplained (idiopathic) malodor production for trimethylaminuria using a standard choline challenge. We also collected basic demographic information.

Results: Approximately one third of patients (118) tested positive for trimethylaminuria. Consistent with previous reports, women, particularly African American women, were significantly overrepresented among trimethylaminuria-positive patients. Of note, the same pattern was seen among trimethylaminuria-negative patients. Also consistent with previous reports, trimethylaminuria-positive women who were still menstruating tended to produce higher levels of trimethylamine within ± 7 days of menses, although this trend was statistically marginal (P = .07).

Conclusion: If our patient sample is representative of patients with idiopathic malodor, demographic information (race and gender) may not be useful in a differential diagnosis of trimethylaminuria. However, undiagnosed cases of trimethylaminuria may be fairly common among patients with idiopathic malodor. If so, choline challenge testing should be indicated for all such patients because trimethylaminuria is responsive to dietary and other treatments. We speculate that testing also might reveal cases of trimethylaminuria among those diagnosed with certain psychologic disorders, including olfactory reference syndrome.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Black or African American
  • Child
  • Child, Preschool
  • Choline
  • Cross-Sectional Studies
  • Diagnosis, Differential
  • Female
  • Humans
  • Incidence
  • Male
  • Menstrual Cycle / physiology
  • Metabolism, Inborn Errors / diagnosis*
  • Metabolism, Inborn Errors / epidemiology*
  • Metabolism, Inborn Errors / ethnology
  • Methylamines / urine
  • Middle Aged
  • Odorants*
  • Sex Factors
  • White People
  • Young Adult


  • Methylamines
  • Choline

Supplementary concepts

  • Trimethylaminuria