Sir,
A 25-year-old male of Fitzpatrick skin type V presented with diffuse greyish-brown hyperpigmentation of 3 years duration, starting over bilateral upper eyelids, and gradually progressed to involve the neck, axillae and flexor aspect of upper limbs over a few months [Figure 1]. It was associated with mild-to-moderate intensity itching and mild bilateral eyelid oedema. History of relapsing and remitting with exacerbation in summers and improvement during winters and with topical steroids, but complete resolution of lesions was never seen. No history of irritant or cosmetics application, prolonged drug intake, photosensitivity or other systemic symptoms before or after the onset of lesions. His palms, soles, scalp, nails, oral and genital mucosae were normal.
Figure 1.
(a and b) Hyperpigmentation over the face and neck
Skin biopsy showed focal parakeratosis, mild spongiosis, hypergranulosis, basal cell vacuolar degeneration, pigment incontinence and sparse lymphocytic infiltrate in the upper dermis [Figure 2]. Patch test with standard Indian series showed 3+ positive reactions to Parthenium (0.1%) [Figure 3a and b]. His baseline investigations, serum cortisol, thyroid profile, blood sugar, serum vitamin B12 and ceruloplasmin levels were normal. After 2 weeks of patch testing, intense hyperpigmentation over the positive test site was noticed [Figure 3c]. Based on history, examination and histopathology, he was diagnosed with pigmented contact dermatitis (PCD) to the Parthenium. He responded well with tapering doses of oral prednisolone, azathioprine, topical calcineurin inhibitors and sunscreen.
Figure 2.
Focal parakeratosis, mild spongiosis, hypergranulosis, basal cell vacuolar degeneration, pigment incontinence and sparse lymphocytic infiltrate in the upper dermis
Figure 3.
(a) Normal skin before patch test. (b) 3+ patch test to Parthenium. (c) Intense hyperpigmentation at the patch test site
PCD first described by Osmundsen in 1970 is a non-eczematous variant of contact dermatitis characterised by hyperpigmentation with little or no signs of dermatitis. Riehl melanosis is a variant of PCD, and the most common causes are fragrances, cosmetics, metals and dyes. While the most common mode of PCD is direct contact with the allergens, airborne allergens as a cause have been sparsely reported in the literature.[1] Clinical features of PCD may overlap with ashy dermatosis and lichen planus pigmentosus (LPP) and it is difficult to differentiate clinically without a skin biopsy and patch test.
Parthenium dermatitis can manifest as various clinical patterns, such as classical air-borne pattern, chronic actinic dermatitis-like presentation, mixed pattern (combination of airborne and Chronic actinic dermatitis (CAD)) dermatitis, hand and feet dermatitis, widespread dermatitis, prurigo nodularis-type, photosensitive lichenoid eruption and few other rare patterns like PCD.[2]
Although the exact pathogenesis of PCD remains uncertain, repeated exposure to low levels of allergens produces a type IV hypersensitivity reaction resulting in basal cell vacuolisation with melanin incontinence, with ultraviolet light exposure playing an important attributing factor as photoexposed sites are predominantly involved.[3] There appears to be a role of pigment-genetic interaction also in PCD as most cases have been found to occur in dark-skinned patients.[2]
Patch test has immense value in the diagnosis of PCD as brown pigment in addition to papules or vesicles may develop at the patch test site.[4] Similar to our patient, three out of seven patients with PCD developed intense, bluish-brown pigmentation at the site of the patch test in about 3 weeks by Osmundsen.[5]
To our knowledge, Parthenium hysterophorus presenting as PCD has never been reported in the literature to date and our case draws attention to this uncommon presentation in dark-skinned populations.
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Written and verbal informed consent for the usage of images in the publication have been properly obtained from the patient.
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Conflicts of interest
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Vesicles in the patch test for parthenium
References
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Supplementary Materials
Vesicles in the patch test for parthenium
