One of the patients had characteristic KSS, while the other patient had a very different disease known as Pearson marrow pancreas syndrome. Complicating the matter, in some cases Pearsons syndrome has been shown to progress into KSS later in life.More recent studies have concluded that mtDNA duplications may also play a significant role in determining what phenotype is present. Duplications of mtDNA seem to be characteristic of all cases of KSS and Pearsons syndrome, while they are absent in CPEO.Deletions of mtDNA in KSS vary in size (1.3–8kb), as well as position in the mitochondrial genome. The most common deletion is 4.9kb and spans from position 8469 to position 13147 on the genome. This deletion is present in approximately ⅓ of people with KSS

Diagnosis
A neuro-ophthalmologist is usually involved in the diagnosis and management of KSS. An individual should be suspected of having KSS based upon clinical exam findings. Suspicion for myopathies should be increased in patients whose ophthalmoplegia does not match a particular set of cranial nerve palsies (oculomotor nerve palsy, fourth nerve palsy, sixth nerve palsy). Initially, imaging studies are often performed to rule out more common pathologies. Diagnosis may be confirmed with muscle biopsy, and may be supplemented with PCR determination of mtDNA mutations. Biopsy findings
It is not necessary to biopsy an ocular muscle to demonstrate histopathologic abnormalities. Cross-section of muscle fibers stained with Gömöri trichrome stain is viewed using light microscopy. In muscle fibers containing high ratios of the mutated mitochondria, there is a higher concentration of mitochondria.
This gives these fibers a darker red color, causing the overall appearance of the biopsy to be described as "ragged red fibers. Abnormalities may also be demonstrated in muscle biopsy samples using other histochemical studies such as mitochondrial enzyme stains, by electron microscopy, biochemical analyses of the muscle tissue (ie electron transport chain enzyme activities), and by analysis of muscle mitochondrial DNA." Laboratory studies
Blood lactate and pyruvate levels usually are elevated as a result of increased anaerobic metabolism and a decreased ratio of ATP:ADP. CSF analysis shows an elevated protein level, usually >100 mg/dl, as well as an elevated lactate level. Management
Currently there is no curative treatment for KSS. Because it is a rare condition, there are only case reports of treatments with very little data to support their effectiveness. Several promising discoveries have been reported which may support the discovery of new treatments with further research. Satellite cells are responsible for muscle fiber regeneration. It has been noted that mutant mtDNA is rare or undetectable in satellite cells cultured from patients with KSS. Shoubridge et al. (1997) asked the question whether wildtype mtDNA could be restored to muscle tissue by encouraging muscle regeneration. In the forementioned study, regenerating muscle fibers were sampled at the original biopsy site, and it was found that they were essentially homoplasmic for wildtype mtDNA. Perhaps with future techniques of promoting muscle cell regeneration and satellite cell proliferation, functional status in KSS patients could be greatly improved.One study described a patient with KSS who had reduced serum levels of coenzyme Q10.