Dermatoscopic Features of Hyper and Hypopigmented Lesions of Dowling Degos Disease.

Sir,

Dowling Degos disease (DDD) also known as reticular pigmented anomaly of the flexures is an autosomal dominant genodermatosis with variable penetrance due to loss of function mutations in the keratin 5 gene.[1] It is characterized by slowly progressing hyperpigmented macules which begins in adult life and involves predominantly the flexures. Additional features include follicular hyperkeratotic papules and pitted perioral scars.[2] Association of dyschromatosis universalis hereditaria (DUH) like hypopigmented macules along with the hyperpigmented macules of DDD has also been reported in the literature.[3]

A 40-year-old male patient presented with complaints of asymptomatic skin lesions of increased pigmentation over neck and axilla along with lesions of decreased pigmentation over abdomen progressing insidiously since 3 years. He had a family history of similar pigmentary changes in his mother. Physical examination revealed slightly raised flat hyperpigmented macules over neck and axilla [Figure 1]. Hypopigmented macules with surrounding hyperpigmentation were present over the abdomen. Palmar pits and alteration on dermatoglyphic pattern was also noted. Face, extremities and oral mucosa were spared. Nails and hair were clinically normal.

Figure 1

(a) Hyperpigmented macules on the neck in reticulate pattern along with hypopigmented macules over abdomen. (b) Hyperpigmented macules on the left axilla in reticulate pattern

Dermatoscopic analysis was performed using a triple light source dermatoscope (Ultracam TLS, Dermaindia, India). Dermatoscopy of hyperpigmented lesion with white light highlighted the follicular pits on the skin surface and polarized light revealed irregular brownish projections around hypopigmented center. The irregular brownish projections represent the elongated rete ridges with pigmentation at tips while the hypopigmented center corresponds to the follicular infundibulum [Figure 2]. Dermatoscopy of hypopigmented lesions with polarized light revealed accentuation of the normal reticular pattern around the hypopigmented center [Figure 3]. Palmar pits under white and polarized light revealed plugging with keratinous material along with breaks in the dermatoglyphic pattern by linear pigmented furrows [Figure 4].

Figure 2

(a) Dermatoscopy of hyperpigmented macule under white light: Follicular pits (red arrowhead), (b) Dermatoscopy of hyperpigmented macule under polarized light: Irregular brownish projections (red arrowhead) around hypopigmented centre (yellow asterisk)

Figure 3

Dermatoscopy of hypopigmented macule: (a) White light, (b) polarized light

Figure 4

Dermatoscopy of palmar pit with keratinous plugging: (a) White light, (b) polarized light

A skin biopsy from hyperpigmented macule [Figure 5] showed antler-like filiform elongation of rete ridges with concentration of melanin at the tips with few dermal melanophages and mild perivascular lymphohistiocytic infiltrate. Follicular plugging and inclusion cysts were also found in a few areas. Histopathology of hypopigmented lesions showed epidermal atrophy with diffuse increase in melanin of the basal layer.

Figure 5

Histopathology of hyperpigmented macule showing antler-like projection of rete ridges with pigment concentration at the tips under x100 magnification with hematoxylin-eosin stain

To our knowledge, dermatoscopic features of DDD has been reported in only two case reports[45] where it was described to have a brown star appearance around a white center. The brown star correlated with antler-like branching of rete ridges while the whitish center relates to the follicular plugs. The brownish projections around the whitish center on polarizing light source in our case resembled this brown star appearance. The accentuated reticular pattern in our case may be a feature of this condition affecting darker skin types.[6] The pits on palm with accentuation of pigmentation at margin along with breaks in dermatoglyphics by pigmented linear furrows is a peculiar feature of DDD and can be used to differentiate other conditions with palmar pits.