Aspartylglucosaminuria: Clinical Presentation and Potential Therapies.

Aspartylglucosaminuria (AGU) is a recessively inherited neurodegenerative lysosomal storage disease characterized by progressive intellectual disability, skeletal abnormalities, connective tissue overgrowth, gait disturbance, and seizures followed by premature death. AGU is caused by pathogenic variants in the aspartylglucosaminidase (AGA) gene, leading to glycoasparagine accumulation and cellular dysfunction. Although more prevalent in the Finnish population, more than 30 AGA variants have been identified worldwide. Owing to its rarity, AGU may be largely underdiagnosed. Recognition of the following early clinical features may aid in AGU diagnosis: developmental delays, hyperactivity, early growth spurt, inguinal and abdominal hernias, clumsiness, characteristic facial features, recurring upper respiratory and ear infections, tonsillectomy, multiple sets of tympanostomy tube placement, and sleep problems. Although no curative therapies currently exist, early diagnosis may provide benefit through the provision of anticipatory guidance, management of expectations, early interventions, and prophylaxis; it will also be crucial for increased clinical benefits of future AGU disease-modifying therapies.

[A family with two children diagnosed with aspartylglucosaminuria-case report and literature review].

OBJECTIVE: The authors sought to investigate the clinical features and characteristics of genetic mutation in patients with aspartylglucosaminuria. METHOD: Clinical data of two pediatric siblings in a family were analyzed retrospectively and relative literature was reviewed in order to study the clinical features, imaging and enzymatic characteristics and genetic mutations. RESULT: Case 1, the proband, male, he was hospitalized at 20 months of age because of fever and hepatosplenomegaly for nine days. This child was of moderate nutritional status and normal development. Blood tests showed hemoglobin 78.0 g/L, RBC3.18 × 10¹²/L, WBC 4.06 × 109/L, neutrophils 0.236, lymphocytes 0.631, platelets 34 × 109/L, C-reactive protein 17 mg/L. Blood biochemistry showed alanine aminotransferase 67.1 U/L, aspartate aminotransferase 74.1 U/L, serum albumin 32.8 g/L, direct bilirubin 10.5 µmol/L, lactate dehydrogenase 301.7 U/L. Bone marrow cytology showed reactive morphological changes in bone marrow cells. Atypical lymphocytes could be seen in both peripheral blood and bone marrow smears. Cranial MRI showed poor myelination. Aspartylglucosaminidase activity in peripheral leucocytes of the proband 5.7 nmol/(g × min) vs. normal control>26.6 nmol/(g × min). On his AGA gene and that of his parents, a heterozygous mutation site located in exon 3, c.392C>T (p.S131L), was identified as a novel mutation inherited from his father. The mutation from his mother has not been detected. The proband was not responsive to the anti-infectious medication, nutritional intervention and symptomatic treatment.He died one month after diagnosis.His elder brother, Case 2, showed fever, recurrent respiratory tract infection and progressive psychomotor regression with hepatosplenomegaly from the age of four years. Cranial MRI revealed extensive symmetrical leukodystrophy in bilateral cerebra, cerebellum and brainstem.He died at the age of six years.Related literature was summarized, and no Chinese AGU cases had been reported; 221 foreign cases were collected. The clinical and imaging characteristics were summarized. Delay in language development was one of the clinical symptoms that the majority of parents of AGU children first noted. CONCLUSION: Patients with aspartylglucosaminuria lack of specific symptoms.For children with unexplained delayed speech and progressive mental retardation, the possibility of AGU should be considered, and efforts be made for enzymatic and genetic diagnosis. c.392C> T (p.S131L) was identified as a novel mutation of AGA gene.

Oligosaccharide analysis in urine by maldi-tof mass spectrometry for the diagnosis of lysosomal storage diseases.

BACKGROUND: There are 45 known genetic diseases that impair the lysosomal degradation of macromolecules. The loss of a single lysosomal hydrolase leads to the accumulation of its undegraded substrates in tissues and increases of related glycoconjugates in urine, some of which can be detected by screening of free oligosaccharides (FOS) in urine. Traditional 1-dimensional TLC for urine oligosaccharide analysis has limited analytical specificity and sensitivity. We developed fast and robust urinary FOS and glycoaminoacid analyses by MALDI-time-of-flight/time-of-flight (MALDI-TOF/TOF) mass spectrometry for the diagnosis of oligosaccharidoses and other lysosomal storage diseases. METHODS: The FOS in urine equivalent to 0.09 mg creatinine were purified through sequential passage over a Sep-Pak C18 column and a carbograph column and were then permethylated. MALDI-TOF/TOF was used to analyze the permethylated FOS. We studied urine samples from individuals in 7 different age groups ranging from 0-1 months to ≥ 17 years as well as urine from known patients with different lysosomal storage diseases. RESULTS: We identified diagnostic urinary FOS patterns for α-mannosidosis, galactosialidosis, mucolipidosis type II/III, sialidosis, α-fucosidosis, aspartylglucosaminuria (AGU), Pompe disease, Gaucher disease, and GM1 and GM2 gangliosidosis. Interestingly, the increase in urinary FOS characteristic of lysosomal storage diseases relative to normal FOS appeared to correlate with the disease severity. CONCLUSIONS: The analysis of urinary FOS by MALDI-TOF/TOF is a powerful tool for first-tier screening of oligosaccharidoses and lysosomal storage diseases.