Oculodentodigital dysplasia (ODDD) and Hallermann‐Streiff syndrome (HSS) share several clinical characteristics. However, while ODDD is a dominantly inherited disorder due to mutations in the connexin 43 gene GJA1, the inheritance pattern of the HSS syndrome is still debated. Overlapping phenotypes have been described. In one of such cases we found a homozygous change at the very conserved R76 codon (c.227G>A, p.R76H), the clinically normal parents being heterozigous carriers of the same mutation. A different base change at the same codon (p.R76S) leads to a complete dominant ODDD phenotype. A case of full‐blown HSS phenotype was also analysed but GJA1 mutations were not found. GJA1 homozygous hypomorphic mutations can result in a phenotype in the HSS/ODDD spectrum.