However, ultrastructural abnormalities of the dermal connective tissue components are discernible in two out of three patients with spontaneous dissection. Ehlers–Danlos syndrome type 4, caused by mutations of the COL3A gene, leads to defective production of the collagen, type III, alpha 1 protein and causes skin fragility as well as weakness of the walls of arteries and internal organs. Marfan syndrome results from mutations in the FBN1 gene, defective production of the protein fibrillin-1, and a number of physical abnormalities including aneurysm of the aortic root.There have also been reports in other genetic conditions, such as osteogenesis imperfecta type 1, autosomal dominant polycystic kidney disease and pseudoxanthoma elasticum, α1 antitrypsin deficiency and hereditary hemochromatosis, but evidence for these associations is weaker. Genetic studies in other connective tissue-related genes have mostly yielded negative results. Other abnormalities to the blood vessels, such as fibromuscular dysplasia, have been reported in a proportion of cases. Atherosclerosis does not appear to increase the risk.There have been numerous reports of associated risk factors for vertebral artery dissection; many of these reports suffer from methodological weaknesses, such as selection bias. Elevated homocysteine levels, often due to mutations in the MTHFR gene, appear to increase the risk of vertebral artery dissection. People with an aneurysm of the aortic root and people with a history of migraine may be predisposed to vertebral artery dissection. Vascular tortuosity or redundancy in young patients is associated with an increased risk of spontaneous dissection.
Familial nasal acilia is a rare congenital defect which is characterized by the complete absence of cilia on the epithelial cells of the respiratory tract. Symptoms are common within ones family and start as soon as one is born, with signs such as respiratory distress, dyspnea, lobar atelectasis, bronchiectasis and neo-natal pneumonia. Other symptoms that occur later in life include chronic moist coughing, chronic sinusitis, chronic otitis media, chronic rhinitis, and recurrence of upper and lower respiratory tract infections.Exact prevalence is unknown, OrphaNet estimates this condition to affect less than 1 out of every million people worldwide. R Soferman et al. described this disorder to be "autosomal recessive". == References ==