Differential Diagnosis of Mucopolysaccharidoses Types I, II, III, IVA, and VI Through Analysis of Leukocytic Inclusions.

Mucopolysaccharidoses (MPS) are lysosomal storage disorders characterized by the accumulation of glycosaminoglycans (GAGs), which can lead to cytoplasmic alterations in leukocytes. The objective of this study was to characterize leukocyte inclusions in patients with different types of MPS and assess their diagnostic relevance. A total of 69 Brazilian patients diagnosed with five MPS types were evaluated through cytological analysis of peripheral blood smears. Distinct leukocyte inclusion patterns were observed in four subtypes. In MPS Type II, small violet cytoplasmic inclusions were present in lymphocytes. In MPS Type III, larger violet inclusions were identified in lymphocytes. Patients with MPS Type IVA showed large, sparse granulations in neutrophils, while those with MPS Type VI exhibited coarse inclusions in all leukocytes, characteristic of the Alder-Reilly anomaly. No leukocyte inclusions were found in MPS Type I. These observations demonstrate that leukocyte inclusions vary according to MPS subtype and may represent a useful auxiliary cytological finding. Their identification may support diagnostic suspicion and contribute to the differential diagnosis of MPS II, III, IVA, and VI, complementing enzymatic and biochemical testing.