Detection of iron deposition in dermal fibrocytes is a useful tool for histologic diagnosis of nephrogenic systemic fibrosis.

Nephrogenic systemic fibrosis (NSF) is a fibrotic disease that presents with a history of renal dysfunction. The differential diagnosis generally includes scleromyxedema, systemic sclerosis, and morphea. Especially, scleromyxedema can be extremely difficult to distinguish microscopically. Although the fibrocytes in NSF are often positive for CD34 and procollagen-I, this is not specific for NSF. We identified positive iron staining in the skin of a patient with NSF and investigated whether this was a specific feature among 9 patients with NSF reported in Japan. We found that 6 of 9 patients showed positive iron staining in the dermal fibrocytes. The amount of iron deposition seemed to have no correlation with the degree of fibrosis or duration of the skin lesions but correlated with apparent history of the use of gadolinium-based contrast agents. As controls, skin biopsies from patients with scleromyxedema, morphea, and systemic sclerosis were evaluated by iron staining. None of these control patients showed iron deposition, indicating that positive iron staining may be specific to NSF and can be a useful tool for NSF diagnosis.