One of his younger brothers (II-2) had been identified as an asymptomatic heterozygous carrier of p.Leu146Pro (NM_000199.4: c.437 T > C in exon 4; NP_000190.1: p.(Leu146Pro)) SGSH mutation and his niece had been diagnosed with mucopolysaccharidosis type IIIA (Sanfilippo disease, see Fig. 1). The gene discussed is SGSH; the disease is mucopolysaccharidosis type 3.