Pigmentary Demarcation Lines in Pregnancy.

Sir,

Pigmentary demarcation lines (PDL) are abrupt lines of transition from deeply pigmented areas to lightly pigmented areas in the skin. Eight different types are described in the literature. Type B PDL have been reported over the legs during pregnancy, and regress after delivery.[1] We are reporting a case with PDL related to pregnancy in Indian skin.

Case Report

A 27-year-old woman came on postpartum day 4 with hyperpigmentation on the posterior aspect of both lower limbs and outer aspect of upper limbs. She started noticing these changes during the last trimester of pregnancy and it became more prominent after her delivery. Her antenatal period was uneventful except for hyperemesis gravidarum and intake of medroxyprogesterone tablets for 1 week during the initial part of pregnancy. The baby was delivered vaginally in occipitoposterior position. On examination, there were well-demarcated areas of hyperpigmentation on the flexoral aspect of both lower limbs which were diagnosed as Type B PDL [Figure 1]. Similar well-demarcated pigmentation was noticed on the anterolateral aspects of both arms suggestive of Type A PDL [Figure 2].

Figure 1

Type B PDL in the patient

Figure 2

Type A PDL in the patient

Type B PDL are reported commonly in association with pregnancy. Type B is the most common type of PDL in pregnancy.[2] These lines are very common in blacks. Seventy-nine percent of black female adults have at least one type of pigmentary demarcation line, with types A and B being present in over 50% of the cases.[2] There are also many reports of Type B PDL in Japanese and Caucasians.[34] Gupta et al. reported a pregnant woman from India, who presented with Type B PDL and generalized cutaneous hyperemia.[5] Kumari et al. reported a case with Type A PDL alone and another case with Type B PDL alone in pregnancy.[6] To the best of our knowledge, ours is the first report of a case having both Type A and Type B PDL in pregnancy from India. There are only few previous reports of concomitant occurrence of Type A and Type B PDL in pregnancy from outside India.[37]

Miura described PDL to correspond to axial lines of Sherrington. These virtual lines, well studied by neurologists, correspond to a subset of lines of Voigt, which separate dermatomes arising from nonconsecutive dorsal roots.[8] Pigmentation has neural control and differences in pigmentation noted across these lines may correspond to the absence of overlap between neural territories controlled by different homoeobox genes.[9] As per the axial–neural theory by Maleville, PDL may become apparent only when subtle variation in pigmentation is apparent between two contiguous dermatomes originating from noncontiguous dorsal roots. The prominence of these embryonic demarcated lines in different areas may be influenced by neural, hormonal and genetic factors. In pregnancy, increase in hormones such as melanocyte-stimulating hormone may trigger the inconspicuous melanocytes more in some of these demarcated areas supplied by specific peripheral nerves leading to prominence of PDL (including Type A and B as in our case).[3]

Since prominence of Type B PDL is more associated with pregnancy, local factors in the pelvis like compression and neurogenic inflammation of nerve roots S1 and S2 by enlarging uterus may be a significant contributing factor for Type B PDL as reported by previous authors.[10] We are postulating that sacral nerve root compression which is more common in occipitoposterior deliveries might have added to aggravation of PDL on lower limbs in our patient after delivery. PDL on the face are fairly common in the Indian population especially among the females.[11] We speculate that Type B PDL also may not be rare in Indian skin type and large population-based surveys are required.