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.