Mucopolysaccharidosis type IIIB (MPS IIIB), also called Sanfilippo syndrome B, is a lysosomal storage disease caused by abnormal degradation of heparan sulfate. It is characterized by progressive neurological deterioration with developmental regression and behavioral abnormalities. Additional clinical manifestations can include musculoskeletal anomalies, hearing loss, respiratory tract anomalies, and cardiovascular disease. Here, we report a second individual with MPS IIIB and chronic pancytopenia. To support our hypothesis of a pathophysiological relationship between these clinical findings, we performed hematological studies in MPS IIIB Naglu-/- mice, which revealed a microcytic anemia as well as a decreased monocyte count, without thrombocytopenia. Hematological findings are thought to be secondary to MPS IIIB even though the exact pathophysiological mechanism remains to be determined. Although it likely represents an uncommon clinical feature, we suggest that complete blood count should be considered as part of the clinical surveillance for individuals with MPS IIIB.
Keywords: Sanfilippo B; lysosomal storage diseases; mucopolysaccharidosis type IIIB; pancytopenia.
© 2025 The Author(s). Clinical Genetics published by John Wiley & Sons Ltd.
