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mitochondrial cytopathies ( mc ) are a rare and complex group of neuromuscular diseases due to a defect in the oxidative phosphorylation ( oxphos ) system .
symptomatic renal involvement in mc has been documented in the form of tubular defects ( complete de toni - debr - fanconi syndrome in severe cases to incomplete proximal tubular defects in milder cases ) , chronic tubulointerstitial nephritis , cystic renal diseases , rare glomerular diseases such as focal segmental glomerulosclerosis due to 3243 a > g trnaleu mutations and coenzyme q10 biosynthesis defects , hypermagnesuria and myoglobinuria
. acute kidney injury ( aki ) as the sole presenting manifestation of clinically latent mc is extremely rare .
we report a case of recurrent episodic aki caused by exercise induced rhabdomyolysis in a patient whose muscle biopsy revealed the diagnosis of mitochondrial myopathy ( mm ) .
a 53-year - old man presented with the complaints of oliguria , generalized bodyache and dark colored urine .
he gave an unusual history of three previous episodes of similar symptoms in the past , at 25 , 36 and 48 years of age .
he had been treated with peritoneal dialysis during the first episode and hemodialysis in the next two , following which he made a complete recovery .
all the four episodes had been preceded by a history of walking long distances prior to the onset of symptoms .
, there was no peripheral edema and his blood pressure was 130/80 mmhg , pulse rate was 100/min and systemic examination did not reveal any abnormality .
his laboratory parameters during the present episode were as follows : serum creatinine 10.2 mg / dl , blood urea 160 mg / dl , serum sodium 128 meq / l , serum potassium 6.1 meq / l and serum bicarbonate 17 meq / l . his packed cell volume was 36% , total white blood cell count was 5000 with normal distribution and no abnormalities detected on peripheral smear examination .
his liver function tests showed serum glutamic oxaloacetic transaminase of 2005 iu / l and serum glutamic pyruvic transaminase 880 iu / l .
the patient underwent three sessions of hemodialysis and attained complete recovery of his renal function .
in view of his clinical history and laboratory data , a provisional clinical diagnosis of metabolic myopathy possibly mcardle 's disease causing exercise induced rhabdomyolysis was considered and a muscle biopsy was performed .
histopathology revealed skeletal muscle fibers with preserved fascicular architecture and no evidence of necrosis or inflammation .
cryostat sections stained with modified gomorri trichrome stain revealed characteristic ragged red fibers ( rrf ) which on histochemical staining showed intense reaction in subsarcolemmal zone for succinic dehydrogenase and nicotinamide adenine dinucleotide tetrazolium reductase .
electron microscopy confirmed the presence of abnormal aggregates of mitochondria in the subsarcolemmal region corresponding to rrf .
a final diagnosis of mm was established based on light microscopy , enzyme histochemistry , special stains , and electron microscopy findings .
the patient was evaluated for other systemic manifestations of mitochondrial disease including progressive external ophthalmoplegia , cardiomyopathy , encephalopathy , hypogonadism , and motor neuron disease , which were negative .
he was counseled regarding his disease condition and urged to refrain from strenuous physical exercises .
he has been compliant and on regular follow - up for the last 10 years with no further recurrence of symptoms .
over the last decades , there has been immense development in the field of mitochondrial diseases with an ever expanding list of pathogenic mitochondrial and nuclear dna mutations causing a wide spectrum of clinically manifest diseases . since
the central nervous system and muscle are frequently involved in mitochondrial diseases , the term mitochondrial encephalomyopathy is commonly used .
acute renal failure is uncommon in mitochondrial diseases and it is extremely rare as a presenting manifestation of the disease . among the various syndromes associated with mitochondrial diseases , isolated myopathy due to defects in oxphos , fits the clinical picture in this patient as he has no other systemic manifestations . the oxphos system , which is embedded in the inner membrane of the mitochondria , is constituted by five enzyme complexes , encoded by two separate genomes , viz . ,
mutations in the nuclear dna show mendelian inheritance whereas primary mitochondrial dna mutations are sporadic or show maternal inheritance as mitochondrial dna is only transmitted from mother to child .
mm may also be acquired , as in the case of antiretroviral therapy for human immunodeficiency virus infection . to the best of our knowledge ,
this is the first report from india of isolated mm in an adult patient presenting as recurrent episodic aki .
irrespective of cause of mitochondrial dysfunction , exercise induced adenosine triphosphate depletion results in intracellular calcium accumulation and myocyte death or rhabdomyolysis , which causes acute renal failure by release of muscle cell contents , especially myoglobin into circulation .
myoglobinuria occurs when myoglobin exceeds 250 ng / ml ( normal 5 ng / ml ) and causes cast formation and accumulation of iron in proximal tubules .
aki ensues due to direct nephrotoxicity of myoglobin as well as its conversion to ferrihemate at a ph < 5.6 which is toxic to renal tubules .
in addition , generation of oxygen free radicals and sequestration of fluids in injured muscles results in volume depletion , aciduria , nitric oxide depletion , and renal hypoperfusion further contributing to acute tubular necrosis .
aki induced by rhabdomyolysis can occur in varied clinical settings such as crush syndrome , trauma , drug overdose , hyperthermia , alcohol abuse , etc .
, hence careful collation of history , clinical presentation and laboratory data are required to ascertain the etiology .
recurrent episodic aki is characteristic of rhabdomyolysis and heightened awareness of the possibility along with appropriate sensitivity to abnormal laboratory values is necessary to reach the diagnosis , which can be corroborated by muscle biopsy when indicated .
the diagnostic workup of renal mc involves amalgamation of multiple modalities , viz . , enzymology and biochemistry analyses including measurement of urine organic acids by gas chromatography / mass spectrometry , molecular genetics , pathology ( histology , histochemistry , and electron microscopy ) and neuroradiology studies , possibly coupled with magnetic resonance spectroscopy . in infants ,
podocyte mitochondrial abnormalities demonstrated by electron microscopy are highly evocative of coq10 defects in early onset steroid resistant nephrotic syndrome , which is a treatable mc .
patients with recurrent rhabdomyolysis related aki should be further evaluated by means of muscle biopsy . a diagnosis of mm warrants counseling of the patient regarding avoidance of physical stresses which may provoke relapses of the disease .
conversely , screening for subclinical renal involvement and monitoring for renal disorders is required in all patients with mc .
screening of family members , keeping in mind possible maternal as well as mendelian pattern of inheritance is also important .
this case is reported not only for its unusual presentation of a rare disorder , but also to highlight the value of reaching a correct etiological diagnosis of aki which can lead to prevention of further episodes of renal failure by counseling and institution of appropriate avoidance measures .
mitochondrial cytopathies ( mc ) are a rare heterogenous group of disorders with frequent multisystem involvement including uncommon renal manifestations 
 . acute kidney injury ( aki ) as the primary manifestation of mc is extremely rare . here 
 , we report a case of recurrent episodic aki in an adult male who was subsequently diagnosed to have mitochondrial disease .