Background Klippel-Feil anomaly (KFA) can be seen in a number of syndromes. We describe an apparently novel syndromic association with KFA.

Methods Clinical phenotyping of two consanguineous families followed by combined autozygome/exome analysis.

Results Two patients from two apparently unrelated families shared a strikingly similar phenotype characterised by KFA, myopathy, mild short stature, microcephaly, and distinctive facies. They shared a single founder autozygous interval in which whole exome sequencing revealed a truncating mutation in MYO18B. There was virtually complete loss of the transcript in peripheral blood, indicative of nonsense-mediated decay. Electron microscopy of muscle confirms abnormal myosin filaments with accompanying myopathic changes.

Conclusions Deficiency of MYO18B is linked to a novel developmental disorder which combines KFA with myopathy. This suggests a widespread developmental role for this gene in humans, as observed for its murine ortholog.