Mutations in BBS2 Cause Apparent Nonsyndromic Retinitis Pigmentosa

PurposeTo identify and functionally test the causative mutations in the BBS2 gene in a family presenting with retinitis pigmentosa and infertility and to generate a bbs2−/− mutant zebrafish.MethodsA female proband and her male sibling were clinically evaluated and genetic testing with targeted next-generation sequencing was performed. Mutations were verified by Sanger sequencing. Protein localization was examined by transient expression and immunocytochemistry in cultured HEK-293T cells. Mutations in the zebrafish bbs2 gene were generated by CRISPR/Cas9 and retinal phenotypes were examined by immunohistochemistry.ResultsThe proband and her brother exhibited reduced visual fields, retinal degeneration, and bone spicule deposits, consistent with retinitis pigmentosa. The brother also reported symptoms consistent with infertility. Compound heterozygous mutations in the BBS2 gene; namely NM_031885.4 (BBS2):c.823C>T (p.R275X) and NM_031885.4 (BBS2):c.401C>G (p.P134R), were identified in the proband and her brother. Both mutations interfered with ciliary localization of Bbs2 in cell culture. Mutation of the zebrafish bbs2 gene resulted in progressive cone degeneration and rhodopsin mislocalization.ConclusionMissense mutations of BBS2 leads to non-syndromic retinitis pigmentosa, but not Bardet-Biedl Syndrome, even though Bbs2 fails to localize to cilia. In zebrafish, the complete loss of bbs2 results in cone degeneration and ciliopathy phenotypes, indicating a requirement for Bbs2 in photoreceptor survival.

ANTI-PD-1 Treatment in a Family with Constitutional Mismatch Repair Deficiency Syndrome with Multiple Cancers from Turkey. Is Cancer Immunoprevention with Checkpoint Inhibitors HAS a Role in CASES with Homozygous Mutationis

Constitutional mismatch repair deficiency (CMMRD) syndrome is a rare childhood cancer predisposition syndrome resulting from biallelic germline mutations of MMR genes and it is poorly recognised by clinicians so far. Here we present affected children of 1st degree consanguinous parents diagnosed with CMMRD syndrome due to germline bi-allelic MSH 6 mutations with multiple cancers and mimicking NF 1 in a family from Turkey A 8-yr-old female,referred with brain tumor with follow up Neurofibromatosis 1 and Familial Mediterranean Fever. One of the female siblings had died of aggressive brain tumor at 4yrs of age, one male sibling due to medulloblastoma, followed by diagnosis of a metachronous metastatic colon adenocarcinoma at 15yrs of age. No additional cancers have been reported in the extended family, with the exception of colorectal cancer in the maternal and paternal great uncle diagnosed at age 45 years, paternal grandfather with brain tumor at 70 age of years and maternal aunt with papillary thyroid cancer at age 50 years. Her physical examination was unremarkable other than 8 to 10 cafe-au- lait spots and hipodense macules with irregular borders on her body. Laboratory tests were normal with low IG G2 levels. Cranial MRI revealed a mass in the left cerebellar region, subcortical hyperdens lesions in fronto-parietal area. She underwent near-total resection,histopathology revealed classic desmoplastic medulloblastoma.Postoperative craniospinal MRI showed no residue or metastasis.Craniospinal RT and CT of CCNU, cisplatin,VCR were given. At initial, due to colon adenocarcinoma history in her family, the colonoscopy was performed which did not reveal any polypoid lesions. In addition, because of the family history, the genetic analysis was carried out and disclosed a novel homozygous single base insertion mutation in exon 5 of the MSH 6 gene ( c.3261dupC/ p.Phe1088Leu ).Five cycles of previously mentioned chemotherapy combination and Nivolumab, obtained by pediatric extended use, was commenced at 3 mg/kg/dose in every 2 weeks as new polyps were detected in the following colonoscopy. After 10th dose,9 polyps were removed of tubular adenoma histopathology .She is still on antiPD1 treatment (18.th dose and in remission. Last colonoscopy revealed only one polyp mm in size. The genetic test results of the family: Blood samples were obtained from parents and siblings. One of the siblings was also found to be homozygous. She is 24- months- old age and has multiple cafe-au-lait spots on her body. She is still under follow up with screening tests for development of possible neoplasms. The parents and the other two siblings ( 11 and 6 years old boys) were heterozygous for the mutation. The male sibling who died from medulloblastoma and metastatic colorectal carcinoma genetic test had revealed same homozygous mutation. Conclusions: As the use of immune modulation for cancer prevention rather than therapy has gained considerable attention, we wonder if 24-months-old female sibling with homozygous mutation will be a candidate for cancer immunoprevention with AntiPD1drugs. We think that an international collaboration is required to evaluate guidelines for screening and treatment of malignancies and to explore prevention strategies patients with CMMRD syndrome. Disclosures Beksac: Amgen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Research Funding, Speakers Bureau; Takeda: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene: Speakers Bureau.

A case of molar-incisor hypomineralization with genetic and environmental influences

Background: Molar-Incisor Hypomineralization (MIH) is a common childhood dental pathology. This paper describes a case with familial involvement and environmental risk factors. Case Description: A 35-year old female has yellowish-brown opacities present on central and lateral maxillary incisors, right and left maxillary canines, right and left maxillary first molars, and right and left maxillary second molars. A 33-year old male sibling has yellowish-brown opacities on the right and left central and lateral maxillary incisors. The male sibling’s fraternal twin does not have evidence of MIH. A maternal grandmother also had evidence of MIH, though involved teeth are not known. Practical Implications: MIH is a condition with both genetic and environmental components. Practitioners should consider both etiologies when patients present with the condition.

Lack of Cardiac Iron in SCD Patients Despite Severe Iron Overload

In sickle cell disease (SCD), transfusions improve blood flow by reducing the proportion of red cells capable of forming sickle hemoglobin polymer. The major and unavoidable complication of transfusions in SCD is iron overload. Patients with significant transfusion load and iron siderosis, often have iron deposit into multi organs, including liver, pancreas and heart. However, patients with SCD may be relatively protected from iron mediated cardiac toxicity as compared to patients with thalassemia and similar transfusion load. Nonetheless while patients with SCD have less iron deposition in the heart it is presumed that severe loading will eventually lead to cardiac involvement. We report here two patients with scd with severe iron overload who had no cardiac involvement. These are an 18 year old female and her 20 year old male sibling, known to have SCD (HbSS) with significant blood transfusions history, once a month or every two weeks for 12 years duration. Both had undergone splenectomy, and multiple hospitalizations for pain crises and acute chest syndrome. They had received intermittent iron chelation therapy for only 2 years. Examination revealed marked hepatomegaly and highly elevated ferritin levels, 11964ng/ml and 7098ng/ml respectively, suggestive of iron overload. Both patients had unremarkable electrocardiogram and echocardiogram. SGPT and SGOT are normal. Both patients are below the 5thpercentile for height, and l the 18 year old girl is pre-pubertal, has growth hormone deficiency and is on treatment. Cardiac, liver and pancreas magnetic resonance imaging with T2* showed normal cardiac structure and function without siderosis ( heart T2*32 ms and 35 ms in the female and male siblings, respectively [normal >20 ms]). There was however considerable liver siderosis with estimated liver iron content 16.6±4.4 mg/g dry weight (female sibling) and 13.9±1.8 mg/g dry weight (male sibling). The corresponding R2* were 646±165 HZ and 541±62 Hz, respectively. Also, there was mild to moderate pancreatic siderosis in the 18 year old female (R2* 111 HZ) and mild pancreatic siderosis in her sibling (R2* 55 Hz) These two cases while consistent with what has been reported are unusual because of the degree of iron ovreloead. It is an unexepected finding that despite such extensive iron deposits in the liver, there is no evidence of cardiac iron. It thus seems that in patients with sickle cell disease, even with extensive liver siderosis and endocrine dysfunction there is sparing of the heart. Collecting and studying such cases may shed light on the mecahins of cardiac protection from iron overload in sickle cell disease. Disclosures No relevant conflicts of interest to declare.