With such mutation within the gamete cells, a pair of medically typical individuals may have repeated succession of children who suffer from certain genetic disorders such as Duchenne muscular dystrophy and osteogenesis imperfecta because of germline mosaicism.
In the first documented case of its kind, two offspring of a French woman who had no phenotypic expression of the AD disorder hypertrophic cardiomyopathy, inherited the disease.
That said, diverging from Mendelian gene inheritance patterns, a parent with a recessive allele can produce offspring expressing the phenotype as dominant through germline mosaicism.
[6][7][8] Diseases caused by germline mosaicism can be difficult to diagnose as genetically-inherited because the mutant alleles are not likely to be present in the somatic cells.
[10] The frequency of germline mosaicism is not known due to the sporadic nature of the mutations causing it and the difficulty in obtaining the gametes that must be tested to diagnose it.
[11] A Moroccan family consisting of two healthy unrelated parents and three offspring—including two with Noonan syndrome, a rare autosomal dominant disorder with varying expression and genetic heterogeneity—underwent genetic testing revealing that both of the siblings with NS share the same PTPN11 haplotype from both parents, while a distinct paternal and maternal haplotype was inherited by the unaffected sibling.