Reticulate acropigmentation of dohi: a case report with insight into genodermatoses with mottled pigmentation.

Reticulate acropigmentation of Dohi also called dyschromatosis symmetrica hereditaria or symmetrical dyschromatosis of the extremities is an autosomal dominant inherited disorder. It is characterized by mottled pigmentation with patchy depigmentation commonly over the back of the hands and feet and sometimes on the arms and legs.

Introduction

Reticulate acropigmentation of Dohi is a rare genodermatosis. It is inherited as an autosomal dominant trait, although autosomal recessive kindreds have been reported.[1] Patients develop progressive pigmented and depigmented macules, often mixed in a reticulate pattern, concentrated mainly on the dorsal extremities. Freckle-like macules are present on the face. Lesions appear in infancy or in early childhood and commonly stop spreading before adolescence. The pigmentation lasts for life. The autosomal dominant form of dyschromatosis symmetrica hereditaria (DSH) is due to mutation in the double-stranded RNA-specific adenosine deaminase gene which encodes a double-stranded RNA-specific adenosine deaminase, an RNA editing enzyme. A gene locus responsible for DSH maps to chromosome 6q24.2-q25.22.[23]

Case Report

A 10-year-old Indian boy presented with hyper and hypopigmented macules over the dorsa of hands and feet [Figure 1]. There were hyperpigmented macules over both palms [Figure 2]. Freckle-like macules were present on his face that were not as numerous as hands and feet [Figure 3]. His detailed examination revealed melanotic macules on the surface of axillaries and over the buttocks. [Figure 4]. Few hyperpigmented macules were present over chest and abdomen. Palmar pits were absent. No mucosal lesions were observed.

Figure 1

Hyperpigmented and hypopigmented macules over dorsum of hands

Figure 2

Hyperpigmented macules over both palms

Figure 3

Freckle like macules over face

Figure 4

Mottled pigmentation over buttocks

He was full-term child of non-consanguinous parents following uneventful delivery. When he was 5-year-old, his parents noticed for the first time the presence of hyperpigmented areas intermingled with hypopigmented areas which first appeared on dorsa of feet and hands. He also developed discrete, small freckles like macules on his face. No history of darkening of lesion after sun exposure or photosensitivity was present. There was no history of photophobia. The lesions were totally asympyomatic. Patient's intelligence was normal and his systemic examination revealed no abnormality. Past medical history was insignificant.

Biopsy of both hyperpigmented and hypopigmented macules was done. Biopsy from hyperpigmented macule showed melanocytes in all epidermal layers and were present in abundance in basal layer. Biopsy from hypopigmented macule showed much less melanocytes [Figures 5 and 6].

Figure 5

Biopsy from hyperpigmented macule showing abundance of melanocytes in basal layer and the presence of melanocytes in other epidermal layers (H and E stain, ×400)

Figure 6

Biopsy from hypopigmented macule showing relatively less melanocytes (H and E stain, ×400)

Discussion

First described in 1929 by Toyama in a 3-year-old boy, DHS is a rare acral type of dyschromatosis which is characterized by development of mottled pigmentation over acral area. Pigmentation begins in infancy or childhood, usually before 6 years of age, and gradually increases in depth and extent. Skin lesions remain localized on extremities in nearly half of the patients and involve face and extremities in the remaining half. Biopsy of hyperpigmented and hypopigmented macules shows basal melanosis and hypomelanosis, respectively.[4] History, physical examination and biopsy findings of our patient were in accordance with DSH.

Other pigmentary disorders which have to be differentiated from acropigmentation of Dohi are Dowling-Degos disease, reticulate pigmentation of Kitamura, dyschromatosis universalis hereditaria, xeroderma pigmentosa.

Dowling-Degos Disease (reticulate pigmented Anomaly of the flexures)[56] is a rare autosomal-dominant cutaneous disorder characterized by spotted and reticulate pigmentation of the flexures. Females are mostly affected. Reticulate hyperpigmented macules start appearing in early adult life affecting the neck, axillae, submammary folds, flexors, elbows, knees and groin. Additional features are comedo-like papules on the back and neck and pitted perioral scars. Itching of the affected areas may be the only symptoms. Histological features include filiform elongation of rete ridges involving the follicular infundibulum and melanocyte proliferation without melanin incontinence.

Reticulate pigmentation of Kitamura: It is characterized by hyperpigmented, atrophic, angulated macules which initially appear over the dorsum of the hands, then gradually extend over the extremities and only uncommonly involves face. Involvement of eyelids is extremely rare. Palmar pits and breaks in the epidermal ridge pattern are characteristic. Histologically, the pigmented macules show epidermal atrophy and an increased number of basal melanocytes.

Dyschromatosis universalis hereditaria (DUH): is a very rare autosomal dominantly inherited pigmentary skin disorder characterized by varying shapes and sizes of hyper- and hypopigmented macules. It presents at birth or develop during infancy.[7] The lesions are usually distributed bilaterally and widely over all parts of the body, with limited lesions over the face and sparing of the palms and soles. DUH is mostly encountered in Japan but it has also been reported from Europe[8] and India.[9-11] It is associated with small stature, high-tone deafness, solar elastosis[10] and grand mal epilepsy.[11]

Xeroderma pigmentosum[12-14] is a disorder with photosensitivity, oculocutaneous pigmentation and early neoplasia resulting from abnormal DNA repair. It is a multisystem disorder involving the skin, eyes and nervous system. The affected children may be normal at birth but develop persistent erythema, acute sun-burn, xerosis and diffuse freckling of the photo-exposed body parts by the age of 6 months to 3 years. Multiple telengiectasias are interspersed among the freckles. Acute sun exposure gives rise to vesiculation, ulceration, crusting and atrophic scarring. On histopathological examination initial lesions shows no specific change. In advanced cases, there is flattening of the rete pegs, heavily laden with pigments.[15] Basophilic degeneration of the dermal collagen, features of solar elastosis and increased vascularity are seen.

Although a significant number of cases have been reported from Japan, reticulate acropigmentation of Dohi is much less common in India. We report this case due to its rare occurrence in this part of the world. Moreover, a discussion of genodermatoses with mottled pigmentation will surely aid in diagnosis of the rare genodermatoses.