A Baffling presentation of a greenish macule on the chest

Sir,

A 30-year-old gentleman with chronic pancreatitis due to SPINK 1 mutation was referred by gastroenterologist for a green-colored lesion on the presternal area of a month's duration. The patient had undergone laparoscopic cholecystectomy a month back. He was referred by the gastroenterologist suspecting the pigmentation to be related to his medical illness. The patient couldn’t recollect any history of trauma inflicted to that site. No history of prior bruise. On examination, there was a diffuse greenish macular pigmentation of 4 × 4 cm size over the presternal area. There were no other remarkable examination findings except for the scars on the abdomen due to the prior surgery.

Initially green pigmentation was thought to be due to biliverdin following a bruise or subcutaneous bleed related to the pancreatitis. Coagulation parameters were within normal limits. But the patient neither could recollect a history of trauma nor had a bruise or red lesion at that site. Incidentally, the patient was observed wearing a pendant made out of copper attached to a thread on his neck [Figure 1]. The copper pendant usually rested on the site where there was a green macule, giving a clue to the puzzle. On wiping the macule with a wisp of cotton dipped in spirit, the macule disappeared. On wiping the pendant with cotton dipped in spirit, a green stain appeared on the piece of gauze, thus dispelling the doubt and concluding the mystery [Figure 2].

Figure 1.

Copper pendant overlying diffuse greenish pigmentation over the sternal area

Figure 2.

Leaching of “patina” from the copper pendant upon wiping with alcohol

The green color stain of skin by copper is because the acidic sweat leaches the copper from the pendant which reacts with chloride and bicarbonate in the sweat thus forming copper salts, namely copper chloride and copper carbonate that are green in color. The oxidation of copper also partly contributes to the coloration. Formation of the colored salts of copper is also attributed by the contact with soap and water.[1] Copper chloride is water soluble which will be removed while bathing, whereas copper carbonate is water insoluble which needs alcohol or acetone for its removal. The formation of green coloration on the surface of copper is called “patination” and the green-colored product is called “patina” or “verdigris” akin to the Statue of Liberty made of copper having a green sheen on its surface.

Green-colored stain can also occur with ornaments made out of silver, gold and brass when it contains copper. To prevent the staining due to the ornaments, a clear nail polish forming a polymer coating on the surface of the metal can be applied which creates a barrier between skin and the metal. A coating of car or jewelry wax can also be applied for the same purpose.

There are previous reports of green pigmentation of hair and nail due to copper.[2,3,4] Isolated case reports of blue green pigmentation of seborrheic keratosis and localized pigmentation induced by subcutaneously inserted copper wire also exists.[5]

Other differential diagnoses for the green pigmentation of the skin include resolving petechiae/ecchymosis, green dyes from clothes, green tattoos and pseudomonas infections.

The green pigmentation of biliverdin in the skin following the oxidation of hemoglobin derived from the blood in the dermis is the most common cause for green pigmentation. Chloroma can present as a green plaque lesion but a reddish-blue lesion is more common wherein diascopy may reveal the green hue.[6] The green coloration of the skin can also be caused by brilliant green (a topic antibiotic the use of which is obsolete), green dyes from clothes and green tattoos. Pseudomonas aeruginosa infection of the burns and cutaneous wounds impart a greenish hue and P. aeruginosa can also cause green nail syndrome.

This case emphasizes the fact that macular lesions of unusual hue should make us suspect exogenous pigmentation.