{"id":"93d136a2-a166-54f7-8159-055300535fbf","stable_key":"7fc92b9e-9cbf-556e-8719-6b5244625250:b12-abs-tcn2-inherited-functional-deficiency","predicate":"associated-with","statement":"Two infant siblings with demonstrated transcobalamin II deficiency developed megaloblastic anemia and systemic B12-deficiency manifestations at three and five weeks despite normal total serum B12.","claim_class":"observational","status":"source_derived_draft","evidence_grade":"ungraded","direction":"positive","is_public":true,"mechanism_event_id":"cb276549-743b-5c19-95fa-1412d5a27182","mechanism_event_label":"Normal total B12 did not exclude a serious carrier deficiency.","subject":{"id":"34d83e40-d5d3-5b96-ae76-5cbf699602c4","slug":"human-inherited-tcn2-deficiency","display_name":"Human inherited transcobalamin II deficiency","entity_type_key":"cellular_process"},"object":{"id":"32338c0b-bc3c-56f8-9228-f82b3be962ee","slug":"megaloblastic-anemia","display_name":"Megaloblastic anemia","entity_type_key":"cellular_process"},"evidence_count":1,"mechanism_event":{"id":"cb276549-743b-5c19-95fa-1412d5a27182","stable_key":"7fc92b9e-9cbf-556e-8719-6b5244625250:b12-abs-tcn2-inherited-functional-deficiency-event","event_type":"observed_intervention","label":"Normal total B12 did not exclude a serious carrier deficiency.","description":"Two infant siblings with demonstrated transcobalamin II deficiency developed megaloblastic anemia and systemic B12-deficiency manifestations at three and five weeks despite normal total serum B12.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"b6d9b937-895d-5e0a-8cc5-0454a0b7d373","slug":"vitamin-b12","display_name":"Vitamin B12 (cobalamins)","entity_type_key":"chemical_species"},"role":"nutrient","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"81bccdbc-ffba-51bb-aa61-bce4b43e4103","slug":"tcn2","display_name":"Human transcobalamin / TCN2","entity_type_key":"protein"},"role":"deficient-carrier","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"34d83e40-d5d3-5b96-ae76-5cbf699602c4","slug":"human-inherited-tcn2-deficiency","display_name":"Human inherited transcobalamin II deficiency","entity_type_key":"cellular_process"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""},{"entity":{"id":"32338c0b-bc3c-56f8-9228-f82b3be962ee","slug":"megaloblastic-anemia","display_name":"Megaloblastic anemia","entity_type_key":"cellular_process"},"role":"target","stoichiometry":null,"state_label":"","sequence_order":3,"notes":""}]},"contexts":[{"dimension":"availability_state","value_text":"machinery_impairment","comparator":null,"unit":null,"notes":"Imported condition classification; unverified.","entity":null},{"dimension":"cross_nutrient","value_text":"false","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Two infant siblings; chromatography/electrophoresis and family binding-capacity studies","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"exposure","value_text":"Inherited TCII deficiency; carrier pattern supported recessive inheritance","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"Two-case family report; DNA variants were not identified and total serum B12 did not measure intracellular delivery.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect.","comparator":null,"unit":null,"notes":"","entity":{"slug":"vitamin-b12","display_name":"Vitamin B12 (cobalamins)","entity_type_key":"chemical_species"}},{"dimension":"organism","value_text":"Homo sapiens","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"plain_language","value_text":"Normal total B12 did not exclude a serious carrier deficiency.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"[hakami-1971-tcn2] Neonatal megaloblastic anemia due to inherited transcobalamin II deficiency in two siblings. (1971). https://pubmed.ncbi.nlm.nih.gov/5096637/ DOI: 10.1056/nejm197111182852103","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"tissue_or_cell_type","value_text":"Systemic B12 delivery/hematopoiesis","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"trigger_kind","value_text":"machinery_impairment","comparator":null,"unit":null,"notes":"Imported condition classification; unverified.","entity":null}],"evidence":[{"id":"a29f9542-1815-5b60-bacf-337ad5ef2fe8","evidence_kind":"source_excerpt","locator":"Lines 530-541","start_line":530,"end_line":541,"excerpt":"### b12-abs-tcn2-inherited-functional-deficiency\nTwo infant siblings with demonstrated transcobalamin II deficiency developed megaloblastic anemia and systemic B12-deficiency manifestations at three and five weeks despite normal total serum B12.\nCondition category: machinery_impairment\nnutrient_topic: Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect.\nplain_language: Normal total B12 did not exclude a serious carrier deficiency.\norganism: Homo sapiens\ntissue_or_cell_type: Systemic B12 delivery/hematopoiesis\nexperimental_model: Two infant siblings; chromatography/electrophoresis and family binding-capacity studies\nlimitations: Two-case family report; DNA variants were not identified and total serum B12 did not measure intracellular delivery.\nexposure: Inherited TCII deficiency; carrier pattern supported recessive inheritance\ncross_nutrient: false\n[hakami-1971-tcn2] Neonatal megaloblastic anemia due to inherited transcobalamin II deficiency in two siblings. (1971). https://pubmed.ncbi.nlm.nih.gov/5096637/ DOI: 10.1056/nejm197111182852103","model_system":"Two infant siblings; chromatography/electrophoresis and family binding-capacity studies","directness":"author_interpretation","verification_status":"source_derived_draft","notes":"Exact curation-document quotation, not publisher quotation. Study references: [hakami-1971-tcn2] Neonatal megaloblastic anemia due to inherited transcobalamin II deficiency in two siblings. (1971). https://pubmed.ncbi.nlm.nih.gov/5096637/ DOI: 10.1056/nejm197111182852103","relationship":"supports","weight":1.0,"link_notes":"","source":{"id":"73145023-2982-5848-aff2-8d8875d6b9c5","stable_key":"import-7fc92b9e-9cbf-556e-8719-6b5244625250","title":"Vitamin B12: mechanisms, deficiency and nutrient interactions (2026-09-17)","document_type":"imported_text","citation_label":"AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text.","file_path":"","sha256":"ad5b3a51d36e856aa7fdfd1cc23f690b094689bad87d28e1a621a54675a01c92","revision_id":"118bd616-0c13-549f-bfeb-bc439715b89c","review_status":"unverified_draft","notes":""}}],"relations":[],"conflicts":[],"corrections":[],"research":null}