Histopathological findings in pregnancy associated cutaneous hyperpigmentation

Hyperpigmentation in pregnancy is a common phenomenon, experienced to some degree by up to 90% of pregnant women. It mainly involves sun‐exposed areas, but it can extend to non‐exposed zones. Cases with extensive hyperpigmentation are rarely reported. In this paper, we describe the case of a 30‐year‐old phototype V woman in her 37th week of pregnancy, who presented with brownish hyperpigmentation of the skin in extensive areas, including both axillae, the abdomen and the lowest part of the back. In the abdomen, there was a reinforcement of the hyperpigmentation through the linea nigra and the umbilicus. The hyperpigmentation affected the buttocks as well and involved the intertriginous area between them. Histopathologic analysis showed a hyperpigmented basal layer of the epidermis with no melanocytic atypia or melanocytic nests. Histochemical staining for iron did not show any deposits. Immunohistochemical studies for HMB‐45, Melan A and SOX10 demonstrated an increased number of melanocytes. There was hyperpigmentation of basal layer keratinocytes. We also performed immunohistochemical stains for estrogen and progesterone receptors, which were both negative. The patient was examined 3 months after delivery, evidencing a significant clearing of the lesions.