Phenotypic overlap in Melnick-Needles, serpentine fibula-polycystic kidney and Hajdu-Cheney syndromes: a clinical and molecular study in three patients

Several disorders characterized primarily by anomalies of the skeleton have recently been shown to be caused by mutations in the X-linked gene, FLNA. One of these conditions, the Melnick-Needles syndrome exhibits a phenotype that shares overlap with that of serpentine fibula-polycystic kidney syndrome and the autosomal dominant condition, Hajdu-Cheney syndrome. Here, we describe three individuals with these diagnoses. The individual with serpentine fibula-polycystic kidney syndrome, the fifth case reported in the literature, exhibited wormian bones which further expands the phenotypic spectrum for this condition and extends the overlap with Hajdu-Cheney syndrome. All three members of the filamin gene family, FLNA, and its functionally related paralogues, FLNB and FLNC, were screened for pathogenic mutations in all three individuals. We found a mutation in FLNA in the individual with Melnick-Needles syndrome, but no pathogenic variants in any filamin gene in the two individuals with Hajdu-Cheney syndrome and serpentine fibula-polycystic kidney syndrome. Clinical and molecular evidence indicates that Melnick-Needles syndrome is aetiologically distinct from Hajdu-Cheney syndrome and serpentine fibula-polycystic kidney syndrome, but these two latter conditions share many clinical similarities and may prove to be allelic to one another.