Phenotypic overlap between McKusick-Kaufman and Bardet-Biedl syndromes in two Egyptian families

Background McKusick-Kaufm an syndrome (MKKS) and Bardet-Biedl syndrome (BBS) are two conditions that can initially overlap in their clinical features. Patients and methods With time, additional features such as retinitis pigmentosa, obesity, learning disabilities, and progressive renal dysfunction can develop in both syndromes. Thus, clear phenotypic differentiation between BBS and MKKS is not feasible. Herein, we describe patients from two unrelated families who presented with clinical features suggestive of both MKKS and BBS. Molecular studies of the MKKS gene revealed a known pathogenic variant in exon 3, c.295T>C (p.C99R) in family 1. On the contrary, a novel likely pathogenic variant in exon 6 (c.1519G>T, p.E507*) was identified in family 2. Results Our results add more evidence that MKKS and BBS are genetically heterogeneous disorders with mutations resulting in a wide spectrum of phenotypically overlapping features. Conclusion We suggest that both MKKS and BBS be included as one entity in the ciliopathies group.