Pigmented colloid milium associated with exogenous ochronosis in a farmer with long-term exposure to fertilizers.

Background: Colloid milium is a rare cutaneous deposition disorder characterized by translucent papules developing on sun-exposed regions such as the face, neck and dorsal aspects of the hands and back. Exogenous ochronosis is caused by the accumulation of homogentisic acid resulting from long-term application of certain topical agents. Histology is characterized by yellow-brown pigment deposits in the papillary dermis. Prolonged use of hydroquinone may result in the development of the pigmented form of colloid milium, sometimes in association with ochronosis.

Case report: A 53-year-old man presented with a 3-year history of multiple slow spreading pigmented papules on the dorsa of his hands, nose and ears. The patient had a long history of exposure to sun and fertilizers with no history of using hydroquinone bleaching creams. A later biopsy revealed the diagnosis of pigmented colloid milium associated with exogenous ochronosis.

Conclusion: UV light damage and long contact with fertilizers may have a role in the development of pigmented colloid milium associated with exogenous ochronosis.