Homozygous microdeletion of the ERI1 and MFHAS1 genes in a patient with intellectual disability, limb abnormalities, and cardiac malformation.

A male child, born from consanguineous parents and having intellectual disability, short stature, dysmorphic facial features, synpolydactyly, and cardiac malformations is reported. Chromosomal microarray analysis showed that the patient presents with an 8p23.1 homozygous deletion, containing the microRNA miR-4660, the exoribonuclease 1 (ERI1), and malignant fibrous histiocytoma amplified sequence 1 (MFHAS1) genes. The microRNA miR-4660 has no known function. MFHAS1 is an immunomodulatory protein involved in Toll-like receptor signaling, erythropoiesis, and cancer. ERI1 is a ribonuclease involved in RNA metabolism and is required for the correct patterning of the skeleton by defining the HOXC8 expression. We discuss the involvement of these deleted genes to the patient's features and highlight differential diagnoses with syndromes implicating limb extremity abnormalities such as synpolydactyly, including the monosomy 8p.