Introduction
In a recent article Meldau et al. reported about 2 black South African pediatric patients with neuro-hepatopathy due to the variant c.
106C
>T in the
MPV
17
gene[ 1]. We have the following comments and concerns.
The authors claim that hypotonia was “central”. However, patient-
2 had reduced tendon reflexes and both patients had proximal muscle weakness[
1] , suggesting “peripheral” hypotonia. “Central” hypotonia implies that there was cerebral involvement in the two patients. Thus, it would be interesting to know if cerebral imaging was carried out in any of the
2
4 homozygous carriers of the
MPV
17
variant. Clinical cerebral abnormalities have been previously reported in carriers of
MPV
17
variants and include microcephaly [
2] , dystonia[
2] , nystagmus[
2] , or failure-to-thrive [
2] . Abnormalities on imaging include leucoencephalopathy[
3] , subdural hemorrhaghes[
2] , or peri-ventricular leucomalacia[
2] , T1W hyperintensities, representing delayed myelination, in the anterior limb of the internal capsule and the corpus callosum splenium [
4] , and T2W hyperintensities in the reticular formation of the lower dorsal brain stem and the reticulospinal tracts of the cervico- medullary junction [
4] .
Since both patients had marked liver involvement and since hepatopathy in
MPV17 carriers may go along with hyper-ammonemia, it essential to report serum ammonia levels. Assuming that there was hyper- ammonemia, it is conceivable that cerebral involvement was rather secondary (hepatic encephalopathy) than primary (leucoencephalpathy).
MPV17 variants may also cause mtDNA depletion [
5] . Were the 24 patients investigated for mtDNA depletion and did the authors find mtDNA depletion or multiple mtDNA deletions in any of these patients? Myopathy has been particulary reported in
MPV17-assocaited mtDNA depletion.
In conclusion, this case study could be more meaningful if cerebral imaging studies would have been provided, if the effect of the
MPV17 variant on the amount of mtDNA would have been investigated, and if hepatic encephalopathy would have been excluded.