A young white girl had a peculiar poikilodermatous pigmentary disturbance and a megaloblastic anemia. Both changes were resolved with vitamin B12 therapy. Epidermal cells in areas of pigmentation were found to have abnormally large nuclei similar to those previously described in the mucosal epithelium of patients with vitamin B12 deficiency. The epidermal nuclear size returned to normal following treatment, supporting the assumption that these enlarged nuclei were indicative of the deficiency. The data suggest that a common mechanism linked with the vitamin B12 deficiency state may be responsible for both the pigmentary disturbance and the cytologic abnormality. The absence of cytologic changes in the skin of normally pigmented areas in this patient and in a second case of vitamin B12 deficiency without a pigmentary disturbance is consistent with this theory.
Gilliam JN, Cox AJ. Epidermal Changes in Vitamin B12 Deficiency. Arch Dermatol. 1973;107(2):231-236. doi:10.1001/archderm.1973.01620170043012