THBS1 and microphthalmia: However, although R1034C segregates completely with disease in family 1, the fathers in families 2 and 3 have not been diagnosed with early-onset disease, suggesting that these THBS1 missense alleles may result in disease with variable expressivity and severity, similar to other childhood glaucoma resulting from the genes MYOC, EFEMP1, TEK, ANGPT1, and MAB21L1 (a gene causing microphthalmia) (9, 10, 12, 13, 21).