Vietnamese child links ADAR nonsense variant to inherited pigment disorder
A Vietnamese child with mottled hyperpigmented and hypopigmented macules on the dorsal hands and feet carried a heterozygous ADAR nonsense variant, c.1944C>A (p.(Tyr648Ter)), in a molecularly confirmed case of dyschromatosis symmetrica hereditaria. The same variant was also identified in his mother, fitting the autosomal dominant inheritance pattern that often defines this genodermatosis. In practical terms, the report moves the diagnosis beyond a descriptive skin phenotype and into the molecular territory that increasingly shapes how inherited pigmentary disorders are recognized, counseled, and classified.
The child’s cutaneous pattern is the classic clinical starting point. Dyschromatosis symmetrica hereditaria presents with a mixture of hyperpigmented and hypopigmented macules, typically on acral surfaces such as the dorsal hands and feet, where the pattern can be striking yet easily confused with other pigmentary conditions if family history and genetics are not considered together. A diagnosis based only on appearance may miss the underlying mechanism, especially in settings where access to dermatologic genetics remains uneven. Here, the molecular result provided a direct explanation for the phenotype and reinforced that the disorder can be tracked through the family line rather than treated as an isolated dermatologic curiosity.
The identified variant introduces a premature stop codon in ADAR, the gene encoding adenosine deaminase acting on RNA. Loss-of-function changes in this pathway are biologically plausible drivers of abnormal pigmentation because ADAR-mediated RNA editing influences cellular programs that help maintain normal melanocyte function and skin patterning. When this editing system is disrupted, the downstream effect can be patchy instability in pigment production, leaving the skin with adjacent areas of excess and reduced color. A nonsense variant is especially relevant because it is expected to truncate the protein and can meaningfully impair function, which is why the alteration was classified as likely pathogenic.
The family finding matters as much as the variant itself. Detection of the same heterozygous change in the mother supports vertical transmission and makes the inheritance pattern clinically coherent. For counseling, that distinction matters immediately: once a familial pathogenic or likely pathogenic variant is identified, the conversation shifts from uncertainty about cause to discussion of recurrence risk, cascade testing, and the possibility that other relatives may carry the same alteration even if their manifestations are subtle. In inherited dermatoses with variable expressivity, a parent may have a milder phenotype or may never have been formally diagnosed despite carrying the same molecular lesion.
Molecular confirmation changes how acral pigmentation is interpreted
The case also shows why molecular testing is increasingly important in pigmentary disorders that overlap in appearance. Acral mottling can prompt consideration of a broad differential diagnosis, but the presence of a confirmed ADAR variant places the condition on firmer genetic ground. That is especially relevant when clinicians are trying to distinguish a hereditary dyschromia from acquired pigmentary change or from other inherited conditions that can produce mixed areas of hyper- and hypopigmentation. The genetics does not replace the bedside examination; it anchors it.
In daily practice, the value of a confirmed diagnosis extends beyond nomenclature. A child with a stable inherited pigmentary disorder may otherwise undergo repeated reassessment as new lesions appear or as the pattern becomes more obvious with age. A genetic result can reduce diagnostic drift, limit unnecessary investigations, and guide families toward surveillance that is tailored to the condition rather than to a broad, uncertain pigmentary syndrome. For rare disorders, that precision is often the most meaningful intervention available.
Rare Vietnamese case adds to the dyschromatosis symmetrica hereditaria literature
This case is also notable because it represents one of the few molecularly confirmed reports of dyschromatosis symmetrica hereditaria from Vietnam. Population-specific documentation matters in inherited disease, not because the disorder changes its biology across borders, but because under-recognition is common when a condition is uncommon in local clinical experience. Reporting a confirmed variant in a Vietnamese family widens the geographic and genetic record for the disease and may help clinicians elsewhere recognize similar patterns in patients who would otherwise be labeled with nonspecific pigmentary change.
The variant itself had not been previously reported, which expands the mutational spectrum of ADAR in this disorder. Even a single-family observation can be useful when it adds a clearly described genotype-phenotype pairing to the literature, particularly for rare conditions where each additional case improves the boundary map of known pathogenic variation. In inherited dermatology, that incremental detail is not trivial. It is how rare disorders become more legible to clinicians who may see only one such patient in years of practice.
No specific grants, equipment, or drugs were received for the work, and the authors declared no competing interests. Those disclosures do not affect the clinical meaning of the case, but they frame the report as a focused genetic and dermatologic observation rather than a study shaped by external therapeutic or commercial pressures.
For clinicians facing a child with symmetric acral mottling, the practical lesson is straightforward: dyschromatosis symmetrica hereditaria should remain on the differential when the pattern fits, and ADAR testing can provide the definitive answer when clinical inspection alone is not enough. In this family, the combination of a classic pigmentary phenotype, maternal carriage, and a previously unreported nonsense change offers a compact but important reminder that rare skin disorders often become understandable only when phenotype and genotype are read together.