Discussion
Abnormal growth is a frequent finding in MPS patients. In particular in patients with MPS VI, normal growth is evident until 1.5 years of age and is then followed by growth stunting (-2 to -3 SD at 3.5 and 9 years, respectively).[18] Clinical trials with ERT have shown a slight improvement in growth rate (height), which is not statistically significant when compared to patients who are not on treatment.[19] An analysis of the patient’s growth chart shows evidence of persistently low height for age (z-score<-2SD) a z-score measurement (-4.15) consistent with the mean reported by Quartel et al. [20] and Hsiang-Yu lin et al. [21] for untreated patients with MPS VI. This is consistent with the limited effect on growth found in Italian and Taiwanese patient cohorts treated with ERT. [16,19] As shown in Figure 2, a progressive increase in weight (z-score +1.63 to +2.4) and BMI (obesity ranges) was documented. These findings prompted probing into eating habits and physical activities, revealing a hypercaloric diet and sedentarism, the latter due in part to challenges with physical activity secondary to the disease. This explains patient obesity, although there is no evidence of metabolic involvement.
Among patients with MPS VI, 96% have cardiac compromise. During follow-up, the patient was diagnosed with mild aortic, mitral and tricuspid regurgitation. The cardiac parameters showed slow progression, which is consistent with reports from clinical trials with ERT, with no evidence of regression of findings but rather a slow, stable course.[13]Moreover, the patient has preserved lung function with no evident progression of the disease.
One of the most striking findings in this patient was the stabilization of urinary GAG levels. Measured levels support functional improvement with the treatment both from the pharmacodynamic as well as the biochemical standpoints, supporting stabilization of disease progression.[13,16]
Disease stabilization and subsequent prevention of GAG accumulation has resulted in a stable cardiac and pulmonary course, as well as improvement of joint pain, fine motor skills, speech and motor skills, enabling the child to continue in school, with adequate socialization. These are relevant outcomes resulting from the use of ERT.
During the follow-up period in clinical trials carried out in developed countries, patients on ERT are shown to have a high rate of adherence to treatment (94.6%). However, these data do not reflect what happens in real life in Latin American countries where, despite the unavailability of ERT adherence statistics, it is estimated that compliance with treatment is lower. [13] In this patient, even in the face of challenges to ensure adequate follow-up, treatment was discontinued only in rare occasions because, as a beneficiary of special insurance coverage, the patient has had access to treatment and home infusions, with ensured adherence.
One of the limitations of this case report was the inability to ensure regular patient follow-up through office visits and regular testing as planned. However, the patient was followed in terms of clinical growth measurements, ophthalmological assessment, cardiovascular, neurological and endocrine function, showing limitation of disease progression and absence of drug-related adverse events.