GANAB-related Polycystic Kidney Disease Mimicking the Cutaneous Findings of Neurofibromatosis Type 1

Pathogenic GANAB gene variants are a rare cause of autosomal dominant polycystic kidney disease (ADPKD). With only few reported cases, the phenotypic spectrum of GANAB-related disorders is still emerging. Although kidney and hepatic cysts are well-documented, cutaneous manifestations are not recognized features of GANAB-related ADPKD. Here, we report GANAB-related ADPKD in a 59-year-old woman with multiple café-au-lait macules and axillary freckling. Targeted NF1 and SPRED1 gene testing was negative. Genome sequencing showed a heterozygous pathogenic germline variant, GANAB (c.181C>T, p.Arg61∗). Magnetic resonance imaging confirmed the presence of numerous hepatic cysts and multiple cysts bilaterally in the kidneys. Our findings suggest that the phenotypic spectrum of GANAB-related disorders may include café-au-lait macules and axillary freckling. Because this observation is based on a single individual, the association may be coincidental and should be considered hypothesis-generating. Careful documentation of additional cases will be required to clarify whether pigmentary findings represent a recurrent feature of GANAB-related disease or an incidental finding.