Staphyloma is an abnormal human pregnancy characterized by interstitial chorionic villous edema with a lack of embryonic development or abnormal embryonic development. The incidence of staphyloma is most commonly sporadic rather than recurrent, with an incidence of 1 per 1000-1500 pregnancies in South America, but higher rates in Latin America, the Middle East and the Far East. In China and East Asia, the incidence of staphyloma is 7-10 times higher than that in North America and Europe, with the highest incidence in Zhejiang Province, China, at 1 per 120-700 pregnancies; in Europe and America, the incidence of staphyloma is significantly higher in yellow than in white. The risk of having a second pregnancy after one staph is 1-6%, while the risk of having a second pregnancy with a poor birth outcome is as high as 10-20%; the risk of having a second pregnancy after a second staph increases to 20-30%. Staphylococci can be classified as complete or partial based on visual and microscopic features, karyotype analysis and clinical presentation. BiCHM is a unique type of staphylococcal fetus, accounting for about 20% of complete staphylococytes, often with familial onset and recurrence, with almost no normal pregnancies during the lifetime of the patient, either miscarriage, stillbirth or gravidity. BiCHM is a unique type of staph that accounts for approximately 20% of complete staph pregnancies. This type of familial clustering and recurrence is known as familial recurrent staphyloma, FRM.
FRM is a Mendelian autosomal recessive disorder that occurs repeatedly in two or more family members in a single family line. Studies have shown that FRM is a genetic background of biparental chromosomal origin, and that the same FRM patient can have recurrent staphylococytes when married to different sexual partners, suggesting that the cause of BiCHM may not be a genetic defect in the staphylococcal tissue, but rather a defect in some genes in the pregnant woman that involves the egg. In several cases of familial recurrent staphyloma, no history of staphyloma or abnormal pregnancy was found in the previous generation of family members, and only women in the family were affected, and the mother and daughter of the patient did not develop the disease. Only sisters are affected. It was also found that consanguineous marriages were common in the family line. The analysis of the family tree of familial recurrent staphylococytes suggests an autosomal recessive form of inheritance in the affected family members, and the fact that the same patient had recurrent staphylococytes after marriage with different sexual partners suggests that these women may have a genetic defect affecting the function of the egg. In 2006, a candidate clone approach was used to identify the NLRP7 gene, a pathogenic gene associated with partial recurrent staph and poor reproductive outcome. To date, several research institutions have reported that 42 different NLRP7 gene variant loci have been identified in patients with recurrent staph in different ethnic groups, thus demonstrating that the NLRP7 gene is an important pathogenesis-related gene in recurrent staph. These variants include terminator alterations, rearrangements, small deletions, insertions, spliceon alterations and nonsense mutations. Mutations in the NLRP7 gene double locus are present in approximately 85% (28/33) of reported patients with familial recurrent staphyloma. We screened 35 patients with recurrent pregnancy loss (at least one of which was a staph) of Chinese ethnicity for mutations in the NLRP7 gene. NLRP7 gene mutations were found in 11 patients (31.4%), 7 patients with double locus mutations, 4 patients with single locus mutations, and only 2 patients with pureton mutations, 23 of whom were patients with recurrent staph, and 11 patients (48%) were found to have NLRP7 gene mutations at least at one locus. The NLRP7 gene mutation rate was 81% in Pakistani RHM patients (11 cases) compared to 84% in Indian ethnic RHM patients (13 cases).