COL1A1 Mutations Presenting as Descending Perineum Syndrome in a Young Patient With Hypermobility Syndrome

A 22-year-old woman presented with 12 years of progressive constipation; she had increased joint flexibility, hyperextensible skin, and excessive perineal descent on examination. Radiological studies confirmed evidence of rectal evacuation disorder due to descending perineum syndrome, enterocele, and rectocele. In a wide genetic screen (∼611,000 single nucleotide polymorphisms), 4 variations were identified in COL1A1 gene ([rs72656352, Chr17: 50,185,535-50,185,539, deletion], [rs72654794, Chr17: 50,188,575, deletion], [rs72667023, Chr17: 50,198,170, deletion], [rs67828806, Chr17: 50,198,177 G→C]). These mutations result in an increase in the number of base pairs in the C′ end, as well as replacement of the glycine amino acid in the N′ end, leading to incomplete cleavage of procollagen by proteases and resulting in collagen weakness. Our observations suggest that COL1A1 gene mutations are plausible biological factors predisposing to descending perineum syndrome in association with joint hypermobility in this patient.