A scoring system to predict disease severity in
PGM1-CDG (former CDG It)
A treatable Congenital Disorder of Glycosylation with no central nervous system involvement.
By Fiona Waddell
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Sunnie Yan-Wai Wong, BA, MD/PhD Candidate at Tulane University School of Medicine (New Orleans, USA) created with her team a rating scale to evaluate measurable clinical features of PGM1-CDG (former CDG It). This is important for early recognition and diagnosis, which is essential for proper management and improving clinical outcome.
Congenital Disorders of Glycosylation (CDG) are a group of genetic diseases that are caused by defects in protein glycosylation. Phosphoglucomutase-1 deficiency (PGM1-CDG, read more HERE) was recognised recently and one of the tasks of this enzyme is the storage of sugar (energy), even if this energy is not needed, in order to release energy when it is necessary. Another task of the enzyme is to paste sugars to proteins. When this enzyme is not working, there may be a variety of clinical manifestations, including hypoglycaemia, congenital malformations, early-onset of dilated cardiomyopathy, growth retardation, hormonal deficiencies, hepatopathy, haemostatic anomalies and myopathy. Interestingly, PGM1-CDG is one of the few CDG's that has no central nervous system involvement and has been clinically shown to be tratable; therefore, early diagnosis is important.
Wong evaluated 27 patients with PGM1-CDG who were divided into 3 phenotype groups: severe, moderate and mild. She and her team developed a scoring system, the Tulane PGM1-CDG Rating Scale (TPCRS). This scale evaluates PGM1-CDG disease severity based on the patients' clinical history and presentation. They examined the relationship between genotype, enzyme activity and the TPCRS score.
The research showed that there was a great diversity in the phenotype spectrum. Hepatopathy is the most frequent clinical manifestation, followed by hypoglycaemia, congenital malformation and growth retardation. It also showed that genotype and enzyme activity does not have any significant correlation with the TPCRS score. There were 5 clinical features identified that are strongly associated with one another and are predictive of disease severity: congenital malformation, cardiac involvement, endocrine deficiency, myopathy and growth. Congenital malformation and growth retardation can be evaluated by physical examination, without the need for specific diagnostic testing and thus allow for rapid assessment and initiation of therapy.
It is important to note that long-term follow-up data are not available for some of the patients and disabling symptoms may appear later with time. Although liver involvement and haemostatic anomalies do not have clear correlations with disease severity, these clinical features are common in PGM1-CDG and require timely and proper treatment. The TPCRS can be repeated on patients over time, for monitoring disease progression and responsiveness to therapeutic treatment.