Unmasking NF1 mosaicism: optical genome mapping identifies a novel t(15;17) translocation in melanocytes.

Reciprocal translocation t(15;17) disrupting NF1, detected by optical genome mapping

A young woman referred for reproductive counseling with unilateral pigmentary lesions suggestive of mosaic NF1 had no conventional molecular confirmation on blood. A combined approach using melanocyte culture and optical genome mapping (OGM) identified a reciprocal balanced translocation disrupting NF1: t(15;17)(q26.1;q11.2). This first report of a reciprocal translocation in mosaic NF1 highlights the diagnostic utility of OGM in suspected cases where conventional approaches fail.

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This case perfectly illustrates the limitations of conventional molecular diagnostics in cutaneous mosaic NF1: skin biopsies contain very few melanocytes, rendering standard SV detection unfeasible. Melanocyte culture coupled with OGM represents an elegant solution for mosaic NF1 patients without variants identified by standard WES/NGS.

Clinical impact: 2/3 · Evidence quality: 1/3 · Novelty: 2/2 · Sample size: 0/1 · Journal quality: 1/1 → Total: 6/10