Rapid detection by hydrops panel of Noonan syndrome with PTPN11 mutation (p.Thr73Ile) and persistent thrombocytopenia

BACKGROUND: Nonimmune hydrops fetalis (NIHF) is still a challenging diagnosis. The differential diagnosis is extensive and the success of identifying a cause depends on the thoroughness of efforts to establish a diagnosis. For the early diagnosis of NIHF, a virtual gene panel diagnostic tool was developed. The female premature baby in question was delivered via emergency cesarean at 30 + 1 weeks of gestational age (GA) due to rapidly developing NIHF to a healthy mother. The family history was noncontributory. METHODS: DNA of the family was extracted and sequenced by the virtual hydrops panel with whole‐exome sequencing. RESULTS: The hydrops panel revealed Noonan syndrome (NS) with a germline mutation in PTPN11 c.218C>T (p.Thr73Ile). CONCLUSION: The diagnosis of our patient was rapidly confirmed by the hydrops panel. The variant of c.218C>T (p.Thr73Ile) has not yet been described in literature relating to NIHF. Only a few case reports of this variant are known. This particular mutation is associated with Noonan syndrome, congenital heart defect and persistent thrombocytopenia. Few reveal juvenile myelomonocytic leukemia.