Dyschromatosis Symmetrica Hereditaria

Dyschromatosis symmetrica hereditaria (reticulate acropigmentation of Dohi) is an autosomal dominant disorder with freckle like hyperpigmented and hypopigmented macules on the dorsum of the hands and feet, from infancy or early childhood.

It is most frequent in Japan and China, and is caused by variants in ADAR (DSRAD), which encodes an RNA-editing enzyme. Family history is usual, with high penetrance.

The course is stable, and the condition is benign.

Pathophysiology.

Loss of function of the RNA-editing enzyme adenosine deaminase acting on RNA (ADAR) may alter melanocyte function and is also linked to interferon signalling. Other variants of ADAR cause Aicardi-Goutières syndrome, a neurological disease.

• Reticulate mixture of hyper- and hypopigmented macules on the backs of hands and feet, which can extend to the forearms and legs.
• Freckle like macules on the face, which can be darker in summer and in cold weather.
• No scale, atrophy or systemic features in typical cases.

• Clinical diagnosis from pattern, onset and family history.
• Skin biopsy is rarely needed: hyperpigmented basal layer in dark macules and fewer melanocytes in pale macules.
• ADAR sequencing for confirmation and counselling.

Differential diagnosis.

• Dyschromatosis universalis hereditaria (generalised distribution).
• Reticulate acropigmentation of Kitamura, Dowling-Degos disease and freckles.
• Xeroderma pigmentosum and chilblain lupus.

• Reassure and explain inheritance (50% risk for children).
• No treatment corrects the pigment pattern. Sun protection and camouflage cosmetics. Q-switched lasers can lighten darker macules, but results vary.
• Genetic counselling.

Monitoring. Review yearly in childhood, then as needed.

Referral and escalation. Dermatology; genetics for counselling.