The most prevalent cause of autosomal recessive juvenile parkinsonism is PRKN mutations. For a study researchers wanted to determine the relationship between genotype and pathology in patients with PRKN mutations. In 8 autopsied patients, they examined the sequence and copy number variation of PRKN, mRNA transcripts, Parkin protein expression, and neuropathology. Biallelic PRKN mutations were found in all of the patients. The missense mutation p.C431F was found in 2 individuals who were homozygous and heterozygous, respectively. Exon rearrangements were found in 7 individuals, including 2 from the same family who had a homozygous deletion of exon 4, and 3 patients who had a homozygous duplication of exons 6–7, a homozygous duplication of exons 10–11, and a heterozygous duplication of exons 2–4. They discovered a compound heterozygous duplication of exon 2, deletion of exon 3, and a heterozygous duplication of exon 2 in the other two cases. However, sequencing of cDNA produced from mRNA revealed two distinct transcripts originating from exon 2 triplication and deletion of exons 2–3 and exons 2–4 duplication and deletion of exons 3–4. Parkin expression was detected in their brains using Western blotting and immunohistochemistry. Subfield-specific neuronal loss and moderate gliosis were seen in the substantia nigra pars compacta. In three cases, Lewy bodies were discovered. A characteristic was peripheral sensory neuronopathy.
The PRKN mutations must be identified through genomic and mRNA analyses. Variable mutations may result in no or little mature Parkin production, and the histopathologic aspects may be comparable.