Emperipolesis: an additional common histopathologic finding in H syndrome and Rosai-Dorfman disease.

H syndrome is a recently described autosomal recessive disorder characterized by indurated, hyperpigmented, and hypertrichotic cutaneous plaques, mainly involving the lower abdomen and lower extremities. Associated systemic manifestations include hepatosplenomegaly, heart anomalies, hearing loss, hypogonadism, low height, and hyperglycemia. H syndrome is caused by mutations in the gene SLC29A3, which encodes hENT3, a member of the human equilibrative nucleoside transporter family. Histopathologically, cutaneous lesions of H syndrome consist of dermal and subcutaneous fibrosis with inflammatory infiltrate mostly composed of large histiocytes, some plasma cells, and scattered lymphoid aggregates. Recently, histopathologic and immunohistochemical studies have demonstrated that the immunophenotype of the histiocytes infiltrating the skin of a patient with H syndrome is similar to that of the lesions of Rosai-Dorfman disease. Furthermore, mutations in SLC29A3 gene have also been demonstrated in patients described as having an inherited form of Rosai-Dorfman disease, named Faisalabad histiocytosis or familial Rosai-Dorfman disease. We describe emperipolesis in the cutaneous lesions of a patient with H syndrome, further supporting the relationship between Rosai-Dorfman disease and H syndrome.