Dear editor,
Thank you very much for your letter and advice. It is a great honor for us to submit a
revised version of the manuscript(MS: 3021154126636089) for your consideration.
According to the request, we have included a 'Competing Interests' heading, added the
Authors' contributions part in the manuscript and remove the figure legends in the
additional files and include them in the main manuscript after the reference list. We
have addressed the comments raised by the editors and reviewers carefully. Point by
point responses to the comments are listed as followings.
Reply to Reviewer #1
1. Patient 1 and 2 have infantile onset with severe early manifestation such as
respiratory involvement and NIV support. Authors should discuss the reasons they are
considered later onset (ie No cardiac involvement? No hypotonia?)
Answer: We classified patient 1 and 2 as late onset based on one review of Pompe
disease (Di Rocco M, Glycogen storage disease type II: clinical overview. Acta
Myol. 2007 Jul;26(1):42-4.), which suggesting late onset form has onset at any
age, lack of severe (or absence of) cardiac involvement, progressive skeletal
muscle dysfunction and less dismal short-term prognosis. In our study, although
the age onset of Patient 1 and 2 were earlier than other patients, they had no
cardiac involvement, no enlarged tongue or liver involvement, so we still
considered they were type of late onset.
2. Case 15 is actually carrier of only one mutation, of note the most common, however
measure of GAA level is not available. I think this is important to confirm the
diagnosis even if the muscle biopsy is suggestive.
Answer: We also think the GAA enzyme assay is important for case 15’s
diagnosis. We managed to contact with Patient 15 and detected her GAA activity,
and the result was 3.54 pmol/punch/hr, which was lower than median activities of
normal controls. So Patient 15 is confirmed with the diagnosis of Pompe disease
although she is a carrier of only one mutation. Also, the value has been added
into the table 1. Accordingly, we changed the analysis result of GAA activity as
“The median GAA activity of 16 patients was 2.70 pmol/punch/hour (range,
0–8.05)” on Page 7.
3. The mutation c.2238 G>C is stated to be present in 15 pedigrees. However it is
more correct to say that it is in 15 cases, from 12 families. Indeed last 5 cases actually
belong to 2 families.
Answer: On Page 9, we have changed the “pedigrees” to “patients” in this
sentence as “Our results showed that the majority of our patients (15/27, 55.56%)
carried the c.2238G>C mutation of GAA, and that the allele frequency of
c.2238G>C was as high as 27.08%, making it the most common mutation in this
group.”
More suggestion
1. Adding correlations between the different features of the population studied would
be interesting (for instance biopsy findings and GAA level, or GAA level and age at
onset, CK level and GAA level/biopsy findings, etc)
Answer: Here are the results of correlations between GAA level and age onset,
GAA level and CK level, suggesting there is no obvious correlation between those
factors in our study.
Though it has been reported that there was a trend towards later onset of
symptoms with higher enzyme activities(Herzog A, et al. A cross-sectional
single-centre study on the spectrum of Pompe disease, German patients:
molecular analysis of the GAA gene, manifestation and genotype-phenotype
correlations. Orphanet J Rare Dis. 2012 Jun 7;7:35.), it seems to be no obvious
trend in our study.
We agree that it will be more interesting to discuss the correlation between
different parameters, but we will not discuss this topic for two reasons: 1) the
main point of this paper is to report the GAA mutation pattern in mainland
Chinese patients with late-onset Pompe disease; 2) to answer this question, we
should recruit more patients to confirm correlation between these factors.
2. Cite and comment on this recent work on infantile onset Pompe disease in
Chinese population: Fu L, et al. Gene. 2014 Feb 1;535(1):53-9
Answer: According the study above, the most common mutation in mainland
infantile-onset Pompe patient is not same as the late-onset group, so we added a
sentence on Page 9 as “This result is consistent with findings in Taiwanese Pompe
patients,11 but is different from the common mutation(c.1935C>A),in mainland
Chinses infantile-onset group.23”. Also, we added this paper as Reference 23.
Reply to Reviewer #2:
1.Results Section: the authors state that two patients were diagnosed with either
abnormal liver function or elevated CK. The authors need to clarify whether by
elevated liver function they imply elevated liver transaminases that also may originate
in skeletal muscle. Abnormal liver function should not be used in the manuscript.
Answer: We re-checked the disease history with the patients, and found out that
both of them had hyperCKemia when they had elevated liver transaminases,
implying skeletal muscle disease. So we changed the sentence on Page 6 as “Two
patients presented with hyperCKemia as their initial symptoms.” Also, in Table 1,
there is a change of “high level of serum CK” in Patient 11.
2.Discussion: The authors state that muscle biopsy should be considered to be a very
useful tool as the diagnosis of Pompe disease can be challenging. However, this could
be a point of contention. The authors need to acknowledge that up to 30% of
individuals with late onset Pompe disease may not show specific changes.
Answer: According to our reviewer and Kishnani PS (Kishnani PS, Amartino
HM, Lindberg C, Miller TM, Wilson A, Keutzer J: Methods of diagnosis of
patients with Pompe disease: Data from the Pompe Registry. Mol Genet Metab
2014, 113:84-91.), the muscle biopsy has its limitation in diagnosing Pompe
disease. Hence, we added the sentence on Page 11 that “However, it should be
mentioned that the muscle biopsy still has its limitation in diagnosing Pompe
disease due to the heterogeneity of muscle involvement, especially in patients
with late onset Pompe disease.29” Also, we added the paper above as Reference
29.
3. Minor Essential Revisions: when the authors present data on ethnicity they need
to state that Portuguese are Caucasians. They can talk about data presented on
individuals of Portuguese descent and the rest can be named: subjects belonging
to other Caucasian groups.
Answer: We have changed the sentence on Page 9 that “Although Pompe disease
is rare, it has been reported in a number of different ethnic populations, such as
Caucasian, Taiwanese, Korean and Japanese.” We also deleted “ethnic” in two
sentence in this paragraph as “Other common mutations reported in certain
populations, such as c.1316T>A and c.1857C>G with a frequency of 36.6% in
Korean patients,19 c.1064T>C which is the predominant mutation in Portuguese
patients,20 c.1726G>A with a frequency of up to 27.59% in Japanese patients,21
and the African-American mutation c.2560 C>T,22 were not detected in our
patients. Our study therefore further supports the findings that different
populations have different mutation hotspots.”
All the above is the answer to the reviewers’ comments and the sentences which have
been changed are in red.
Finally, we added three references on pompe disease (Reference 15, 16 and 17) which
were published recently in Chinese journals. All of them were not searchable via
PubMed except one paper. So these two papers have no links to pubmed.
Thank you very much!
Looking forward to receiving your reply
With best wishes,
Yun Yuan M.D.
Dept. of Neurology
Peking University First hospital
Beijing, China