Facial muscles may be involved which lead to atrophy of facial muscle groups producing a thin, expressionless face with some having difficulty with chewing. Neck, shoulder and extremity weakness with atrophy may affect some patients and can be mild or severe.Mild visual impairment was seen in 95% of patients that were evaluated using the Visual Function Index (VF-14).The ciliary muscles that control the lens shape and the iris muscles are often unaffected by CPEO.Additional symptoms are variable, and may include exercise intolerance, cataracts, hearing loss, sensory axonal neuropathy, ataxia, clinical depression, hypogonadism, and parkinsonism.Kearns–Sayre syndrome is characterized by onset before 15 years of age of CPEO, heart block and pigmentary retinopathy. Genetics
Mitochondrial DNA which is transmitted from the mother, encodes proteins that are critical to the respiratory chain required to produce adenosine triphosphate (ATP). Deletions or mutations to segments of mtDNA lead to defective function of oxidative phosphorylation. This may be made evident in highly oxidative tissues like skeletal muscle and heart tissue. However, extraocular muscles contain a volume of mitochondria that is several times greater than any other muscle group. As such, this results in the preferential ocular symptoms of CPEO.Multiple mtDNA abnormalities exist which cause CPEO. One mutation is located in a conserved region of mitochondrial tRNA at nucleotide 3243 in which there is an A to G nucleotide transition. This mutation is associated with both CPEO and mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS).
The Enterobacteriaceae, Acinetobacter species, and Pseudomonas species are intrinsically resistant to rifampicin.It has been used with amphotericin B in largely unsuccessful attempts to treat primary amoebic meningoencephalitis caused by Naegleria fowleri.Rifampicin can be used as monotherapy for a few days as prophylaxis against meningitis, but resistance develops quickly during long-term treatment of active infections, so the drug is always used against active infections in combination with other antibiotics.Rifampicin is relatively ineffective against spirochetes, which has led to its use as a selective agent capable of isolating them in materials being cultured in laboratories. Viruses
Rifampicin has some effectiveness against vaccinia virus. Pathogen susceptibility
The minimum inhibitory concentrations of rifampicin for several medically significant pathogens are:

Mycobacterium tuberculosis — 0.002 – 64 µg/ml
Mycobacterium bovis — 0.125 µg/ml
Staphylococcus aureus (methicillin resistant) — ≤ 0.006–256 µg/ml
Chlamydia pneumoniae — 0.005 µg/ml

Primary biliary cholangitis
Rifampicin is used to treat itchiness caused by primary biliary cholangitis. The treatment-related adverse effects include hepatotoxicity, nephrotoxicity, hemolysis, and interactions with other drugs. For those reasons as well as some ethical concerns regarding off-label use of antibiotics, rifampin as a very effective preventive antibiotic for meningitis, is not considered appropriate for itchiness. Hidradenitis suppurativa
Rifampicin with clindamycin has been used to treat the skin disease hidradenitis suppurativa. Adverse effects
The most serious adverse effect is hepatotoxicity, and people receiving it often undergo baseline and frequent liver function tests to detect early liver damage.The more common side effects include fever, gastrointestinal disturbances, rashes, and immunological reactions.