Laboratory Testing for Angular Cheilitis
In most cases of angular cheilitis, obtain a microbial culture/swab from the lesion to identify bacterial and fungal pathogens, and consider checking vitamin B6 (plasma pyridoxal 5-phosphate), iron studies, and vitamin B12 levels, particularly in refractory or recurrent cases.
Microbial Testing (First Priority)
The primary laboratory investigation should be microbial culture from the lesion itself 1. This is critical because angular cheilitis has a mixed infectious etiology in the majority of cases:
- Staphylococcus aureus is found in 75.5% of cases
- Candida species in 48.4% of cases (including C. albicans and C. stellatoidea)
- Streptococci in 13.5% of cases
- Mixed infections are common 1
The culture helps guide antimicrobial therapy, as the disease frequently involves both bacterial and fungal components 2, 3.
Nutritional Deficiency Screening
Angular cheilitis can be a manifestation of underlying nutritional deficiencies, particularly:
Vitamin B6 (Pyridoxine)
- Plasma pyridoxal 5-phosphate (PLP) is the preferred test
- Normal values: 5-50 mg/L (20-200 nmol/L)
- Important caveat: In inflammatory conditions, use red blood cell PLP measurements instead of plasma, as inflammation falsely lowers plasma PLP but minimally affects RBC concentrations 4
- Vitamin B6 deficiency causes angular stomatitis, seborrheic dermatitis with cheilosis, and glossitis 4
Other Nutritional Tests
- Iron studies (serum iron, ferritin, TIBC) - anemia due to iron deficiency is associated with cheilitis 5
- Vitamin B12 levels - deficiency is linked to angular cheilitis 5
Context-Specific Testing
In HIV-Positive Patients
Angular cheilitis is one of three clinical patterns of oropharyngeal candidiasis in HIV infection 6. If HIV status is unknown or the patient has risk factors, consider HIV testing as angular cheilitis may indicate progressive immunodeficiency.
In Refractory Cases
Consider testing for conditions that increase risk:
- Albumin levels - low albumin affects vitamin B6 interpretation and indicates chronic illness 4
- Renal function - dialysis patients are at higher risk for B6 deficiency 4
- Blood glucose/HbA1c - diabetes increases susceptibility
Practical Algorithm
- Always obtain: Microbial culture/swab from the lesion
- Consider in persistent/recurrent cases: Plasma PLP (or RBC PLP if inflammatory markers elevated), iron studies, vitamin B12
- If immunocompromised or risk factors present: HIV testing, glucose screening
- Adjust vitamin B6 testing: Use RBC PLP instead of plasma PLP if patient has low albumin or signs of inflammation 4
Common Pitfalls
- Don't skip microbial culture - treatment differs significantly between bacterial and fungal predominance 3
- Don't rely solely on plasma PLP in sick or malnourished patients - inflammation causes false-positive deficiency results 4
- Don't overlook systemic causes in recurrent cases - angular cheilitis may be the presenting sign of nutritional deficiency or immunosuppression 4, 5