Congenital dyserythropoietic anemia type III (CDA III) is an extremely rare inherited disorder characterized by ineffective erythropoiesis, multinucleated erythroblasts in the bone marrow, and variable clinical gravity. We report the case of a 6-year-old boy, presenting with abdominal distension, failure to thrive, dark urine, intermittent itching, and recurrent infections. Physical examination revealed pallor, hepatomegaly, and splenomegaly. Laboratory investigations showed mild normocytic anemia, high liver enzymes, and erythroid hyperplasia. The sequencing of the whole exoma identified a variant of uncertain meaning in the KIF23 gene, which is implicated in cytokinesis and attached to the pathogenesis of CDA III. The patient remains clinically stable in support management, without the current need for transfusion. This case highlights the importance of advanced genetic tests in the diagnosis of rare hematological conditions and expands the potential spectrum of mutations associated with CDA III. Early recognition and long-term monitoring are essential for guiding management and monitoring complications such as iron overload and splenomegaly.

Kinesin Family Member 23 (KIF23), a cell cycle regulator, has a key task in cytokinesis. KIF23 over-expression in cancer has been associated with tumor growth, progression, and poor prognosis, indicating a potential to be a cancer biomarker. A mutation in KIF23 (c.2747C > G, p.P916R) was shown to cause congenital dyserythropoietic anemia, type III (CDA III). To-date, fifteen KIF23 transcripts have been annotated, but their expression is poorly investigated. We hypothesized that tissue specific expression of a particular transcript can be critical for CDA III phenotype. In this study, we quantified expression of alternative Kif23 transcripts in a mouse model with human KIF23 mutation and investigated its association with a regulator of alternative splicing, serine/arginine-rich splicing factor 3 (Srsf3). We confirmed presence of an additional exon 8 in both human and mouse KIF23 transcripts. A transcript lacking exons 17 and 18 was ubiquitously expressed in mice while other isoforms were common in human tissues however in bone marrow of knock-in mice a transcript without exon 18 was prevalent as it was in bone marrow of a CDA III patient. We conclude that the possibility that the tissue specific expression of KIF23 alternative transcripts influence the CDA III phenotype cannot be neglected.

The congenital dyserythropoietic anemias (CDAs) are a group of rare genetic disorders characterized by ineffective erythropoiesis and the development of secondary hemochromatosis. Distal limb anomalies are a well-documented though rare feature of congenital dyserythropoietic anemia type I, that have not been reported so far in other types. We describe a patient with congenital dyserythropoietic anemia type II and four members of a family with clinical features of congenital dyserythropoietic anemia type III with distal limb anomalies. The patient with congenital dyserythropoietic anemia type II presented with bilateral complete osseous syndactyly of the hands, and bilateral complete cutaneous syndactyly of feet. Three of the four affected family members with congenital dyserythropoietic anemia type III had partial absence of fingers, small or absent nails, overlapping toes, and short metatarsals. We suggest that similar to congenital dyserythropoietic anemia type I, distal anomalies may appear in some patients with congenital dyserythropoietic anemia types II and III. Patients presenting with anemia and distal limb anomalies should be further investigated for the presence of congenital dyserythropoietic anemia. © 2016 Wiley Periodicals, Inc.