Dermatological Manifestations of Vitamin B12 Deficiency
Vitamin B12 deficiency primarily causes skin hyperpigmentation (most commonly), along with glossitis, angular stomatitis, and hair/nail changes.
Primary Cutaneous Manifestations
Hyperpigmentation
- Hyperpigmentation is the most common dermatological finding in vitamin B12 deficiency, presenting in various patterns 1
- Localized hyperpigmentation typically affects the palmar and dorsal aspects of hands, soles, and flexural areas 2, 3
- Generalized hyperpigmentation can occur but is less common than localized patterns 3
- Melasma-like facial hyperpigmentation has been documented as a rare but reversible manifestation 3
- The mechanism involves melanogenesis stimulation with up to 131% increase in melanin content and 135% elevation in tyrosinase activity, along with reactive oxygen species elevation by 120% causing redox imbalance 4
Oral Manifestations
- Glossitis (inflammation of the tongue) is a characteristic finding 5, 6
- Angular stomatitis (inflammation at the corners of the mouth) occurs frequently 1
- Sore mouth and tongue are common presenting symptoms 2
Hair and Nail Changes
- Hair changes occur but specific patterns are not well-characterized in the literature 1
- Nail changes are documented manifestations 1
Important Clinical Context
Reversibility
- All dermatological manifestations are reversible with B12 supplementation if detected and treated early 2, 3
- Hyperpigmentation resolves after appropriate B12 replacement therapy 2, 7
Diagnostic Pitfalls
- Dermatological symptoms often present before or independently of hematological changes 6
- Up to 50% of patients with "normal" serum B12 levels have functional deficiency when measured by methylmalonic acid 6
- Megaloblastic anemia may be absent in one-third of cases despite significant B12 deficiency 8
Associated Symptoms to Assess
When evaluating dermatological findings, look for:
- Neurological symptoms: numbness, paraesthesia, balance issues, peripheral neuropathy 6, 2
- Cognitive symptoms: memory problems, concentration difficulties 8
- Systemic symptoms: anorexia, weight loss, dizziness, fatigue 2
Treatment-Related Dermatological Effects
- Vitamin B12 therapy itself can cause dermatological reactions, including itching and transitory exanthema 9, 10
- Acne and rosacea are documented complications of cobalamin therapy 1
- Allergic site reactions or anaphylaxis can occur with cobalamin injections 1
- Patients with cobalt sensitivity may develop cutaneous manifestations during B12 replacement 1