Attenuated Phenotype in Hunter Syndrome (Mucopolysacchari dosis type II): Challenges in Clinical Diagnosis

Abstract

ntrodução: Attenuated forms of MPS can be easily overlooked because of paucity of clinical signs. Moreover, they are often misdiagnosed as Legg-Calve-Perthes disease or skeletal dysplasia in presence of prominent skeletal abnormalities and lack of involvement of other systems. Cardiovascular findings can be misdiagnosed as valve disease due to “rheumatic fever”. Unlike most patients with mucopolysaccharidoses (MPS), individuals with Hunter syndrome (MPS type II) do not have corneal clouding and can present with normal intelligence (attenuated phenotype) and mild/no organomegaly. Here we report a 7-year-old boy with normal stature, mild distal fingers
stiffness, normal intelligence, mild valve disease whose first diagnosis was rheumatic fever, although no obvious laboratory finding could confirm this hypothesis. Dermatological evaluation for pebbling of the skin over the scapulae also failed in lead to a diagnosis. Clinical evaluation in medical genetics service pointed out to suspicion
of mild Hunter syndrome, later confirmed by enzyme assay, GAGs chromatography and molecular analysis of IDS gene.In addition, relatively late onset of the disease and absent/minimal clinical signs in the attenuated forms pose great difficulties for the clinicians to suspect such condition. Healthcare providers across specialties should
have in account that mild Hunter patients can present with nonclassical features as mild valve disease or a dermatological condition. Early diagnosis and early treatment significantly improve the clinical outcome and activity of daily living in such patients.