The first proband’s mutation was identified in exon 6 of the NAGLU gene (chr17:40695951C>T c.1927C>T, NM_0000263.3). Both mutations were identified in the proband and confirmed by Sanger sequencing of the family trio (parentage verified). Two compound heterozygous mutations were revealed in the NAGLU gene through whole-exome sequencing (hg19). The level of urinary glycosaminoglicans was increased up to 14.3mg/ mmol (normal range 0-8.3mg/mmol). Brain MRI showed diffuse cerebral atrophy. Abdominal ultrasound exam revealed hepatomegaly. Neurological examination revealed signs of moderate dysarthria and coordination impairment. Upon admission, clinical examination revealed dolichocephaly, narrow forehead, thick eyebrows with synophris, hypertrichosis, prominent philtrum, broad nasal tip, and a thickened lower lip. At the time of admission, the patient was a college student, experiencing fatigue, attention decline, and affective lability that had a severe impact on her studies. Gait impairment and cognitive deterioration progressed over the course of the following years. Her mother first noticed poor coordination, disturbance of articulation and fine motor skills when the patient was three years old. These episodes first started at the age of 6, increasing from 5 to almost 60-70 per night by the age of 16. An 18-year-old female presented to our clinic with a history of disrupted sleep caused by sudden brief awakenings with hypermotor activity, lasting for 5-10 seconds, followed by muscle soreness.

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