Type B pigmentary demarcation lines.

A 29-year-old female presented with 2 months history of asymptomatic, bilaterally symmetrical, non scaly, pigmented band involving buttocks, thighs and legs upto ankles posteromedially [Figures 1 and 2]. The medial border of the pigmentary band was sharply demarcated while laterally it merged imperceptibly into the surrounding normal skin. The pigmentation was noticed by her during the 9th month of second pregnancy. She had not received any hormonal therapy during pregnancy. There was no history of similar pigmentary alteration during previous pregnancy. Her medical and obstetric history were unremarkable. None in the family had similar pigmentation. Based on history and examination, a diagnosis of type B pigmentary demarcation lines (PDL) associated with pregnancy was made.

Figure 1

Type B pigmentary demarcation lines on lower extremities

Figure 2

Close up view of PDL on thighs

DISCUSSION

Pigmentary demarcation lines, also known as Futcher's lines or Voigt's lines, are physiological lines which correspond to borders of abrupt transitions between deeply pigmented surfaces and lighter surfaces. Presently they are classified into 8 types: Type A through H.[1] Out of these, type B is commonly associated with pregnancy usually occurring after the 7th month of pregnancy and regressing after delivery.[2] These lines have been regarded as a physiological change during pregnancy.

The exact pathogenesis of PDL is unknown. They have been considered as an atavistic remnant, where the dorsal skin is pigmented more than the ventral to provide better protection from the sun.[3] Hormonal alterations in the levels of estrogen, progesterone, and melanocyte-stimulating hormone during pregnancy are likely to be involved.[45] Neurogenic inflammation due to trapping of the cutaneous nerves by the enlarging uterus[6] and genetic factors[3] may be contributory. Counseling and reassurance is what is generally required owing to the benign and self limiting nature of the condition.

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Conflicts of interest

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