Fatal infantile mitochondrial encephalomyopathy with complex I and IV deficiencies

Fatal Infantile Mitochondrial Encephalomyopathy with Complex I and IV Deficiencies

the other, s y m p t o m s are e v i d e n t in early infancy with severe systemic i n v o l v e m e n t and early death. In m i t o c h o n d r i a l e n c e p h a l o m y o p a t h i e s - o n e o f the m a j o r causes of congenital lactic a c i d o s i s - several enz y m e defects in the electron transport system h a v e been described, including a fatal infantile f o r m with c o m p l e x IV [1-4], I [5-10], and I and IV deficiencies [ l l ] . We report the clinical features and h i s t o c h e m i c a l and b i o c h e m i c a l findings o f biopsied m u s c l e in a patient with the fatal infantile f o r m o f c o m p l e x I and IV deficiencies.

Case Report

Toshiro Nagai, MD**, Yutaka Tuchiya, MD*, Yutaka Taguchi, MD*, Ryoichi Sakuta, MD*, Takashi Ichiki, MD¢, and Ikuya Nonaka, MD* A 4-month-old male infant had a fatal infantile mitochondrial disease associated with cardiomyopathy. He had elevated lactate c o n c e n t r a t i o n s in blood and cerebrospinal fluid and an increased lactate/pyruvate ratio. Histochemical analysis of muscle biopsy revealed several ragged-red fibers on modified Gomori trichrome stain and mildly decreased cytochrome c oxidase (complex IV) activity. Complex I and IV activities of the respiratory chain in muscle were decreased to about 35% of normal values biochemically; subunits of the two complexes were decreased nonselectively on immunoblotting. Mitochondrial D N A analysis failed to detect any mutation. Complex I and IV deficiencies should be considered as one of the causes of fatal infantile mitochondrial disease.

This male infant was born at 40 weeks gestation, weighing 2,992 gin, after an uncomplicated delivery. He was the second child of normal parents with no family history of consanguinity or neuromuscular diseases. His brother was healthy at 7 years of age. During the first 2 months of life the child exhibited increasing lethargy, hypotonia, difficulty in feeding, and growth retardation. At 2 months of age, he was admitted to our hospital due to irregular breathing. On admission, he was lethargic and weighed 2,968 gm; he responded only to painful stimuli. Initial laboratory data included pH 7.19, bicarbonate 7.3 mEq/L, sodium 140 mEq/L, potassium 4.8 mEq/L, chloride 110 mEq/L, blood glucose 8 grn/dl, blood lactate 117.3 mg/dl (normal: 2.6-16.1 mg/dl), pyruvate 2.0 mg/dl (normal: 0.1-0.9 mg/dl), GOT 507 IU/L, and GPT 136 IU/L. He recovered from metabolic acidosis after sodium bicarbonate administration. During the first 8 days of hospitalization, however, he was weak, hypotonic, lethargic, and fed poorly. Serum amino acid profile revealed an increased level of glycine 638.8 nmol/ml (normal: 181.1268.9 nmol/ml) and alanine 685.2 nmol/ml (normal: 321.9-479.9 nmol/ml). The serum free camitine level was 7 ~tM (normal: 35.5 + 7.7 ~tM), acid soluble camitine 19 ~tM (normal: 52.0 + 9.0 pM), and total

N a g a i T, T u c h i y a Y, T a g u c h i Y, Sakuta R, Ichiki T, N o n a k a I. Fatal infantile m i t o c h o n d r i a l e n c e p h a l o m y o p athy with c o m p l e x I and IV deficiencies. Pediatr N e u r o l 1993;9:151-4.

Introduction T h e causes of c o n g e n i t a l lactic acidosis are variable and it is usually difficult to clarify the m e t a b o l i c defects in affected infants. Clinically, there are t w o m a j o r categories: in one, s y m p t o m s are manifest f r o m late childh o o d through adulthood with progressive deterioration; in

Figure 1. On modified Gomori trichrome stain, there is marked variation in fiber size with a typical RRF: original magnification, x600.

From the *Division of Ultrastructural Research; National Institute of Neuroscience; National Center of Neurology and Psychiatry; ~Department of Neurology; Tokyo Metropolitan Kiyose Children's Hospital; Tokyo, Japan; ~Departrnent of Pediatrics; Nagoya City University Medical School; Nagoya, Japan.

Communications should be addressed to: Dr. Nagai; Division of Ultrastructural Research; National Institute of Neuroscience; NCNP; 4-1-10gawahigashi; Kodalra, Tokyo 187, Japan. Received September 8, 1992; accepted October 29, 1992.

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Figure 2. Electron micrograph of the rectusjemoris muscle of the patient demonstrated an increased number of enlarged mitochondria with disorganized cristae at the subsarcolemmal area: original magnification, x17,500. camitine 24 ~M (normal: 54.7 _+ 8.8 btM). Urine organic acid analysis revealed a high level of excretion of lactate. On the eighth day after admission, he developed respiratory failure and lactic acidosis with a pH of 7.06, bicarbonate 7.7 mEq/L, blood lactate 120.8 mg/dl, pyruvate 2.52 mg/dl, and blood glucose 114 mg/dl. Lactate and pyruvate levels in cerebrospinal fluid were 109.2 mg/dl (normal: I1. I-16.3 mg/dl) and 3.51 mg/dl (normal: 0.75-1.29 mg/dl), respectively. Serum CK ranged from 190 to 473 IU/L (normal: < 110 IU/L) and CK isozyme analysis demonstrated MB of 41% and MM 59%. He developed gradually increasing cardiomegaly and hepatomegaly with oliguria and tachypnea. A two-dimensional echocardiography revealed poor cardiac contraction. On the twenty-forth day after admission, muscle biopsy was performed on the rectus femoris muscle which revealed mitochondrial abnormalities. With a diagnosis of a mitochondrial disorder, he was placed on coenzyme Qt0 with no beneficial effect and he died at the age of 145 days due to respiratory failure. No permission was given for postmortem examination. Muscle Histochemistry and Electron Microscopy. In frozen sections stained with a modified Gomori trichrome and succinate dehydrogenase methods, ragged-red fibers (RRFs) were scattered throughout and comprised approximately 7% of total muscle fibers (Fig 1). They were usually hypertrophic and contained increased amounts of oil-red O positive droplets. Cytochrome c oxidase (COX) activity was moderately decreased with no focal deficiency. No tissue-specific involvement was observed. On electron microscopy, enlarged mitochondria with complicated cristae were increased in number in some fibers (Fig 2). Biochemistry. Enzyme activities in the electron transport system [12] and oxygen consumption test [23,24] were performed by the methods described before [12,23,24]. NADH cytochrome c reductase and COX activities were decreased to 48.1 nmol/min/mg mitochondrial protein (normal control: 131.9 +_ 47.7 nmol/min/mg) and 19.9 nmol/min/mg (normal: 56.4 _+.+ 17.4 nmol/min/mg), respectively. Succinate cytochrome c reductase activity was somewhat increased to 119.7 nmol/min/mg mitochondrial protein (normal: 90.1 _+26.7 nmol/min/mg).

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When NADH-dependent respiratory substrates (pyruvate 5 mM and malate 5 mM) were added to the incubation medium, oxygen consumption at states 3 and 4 were decreased to 34% and 54% of normal values, respectively; when a flavin adenine dinucleotide-dependent respiratory substrate (succinate 5 raM) was added, oxygen consumption rates were normalized. On immunoblot analysis of isolated mitochondria, the amount of immunochemically detectable subunits in complexes I and IV were generally decreased without specific defects, whereas those in complexes Ill and V were normal (Fig 3). Mitochomtrial mtDNA Analysis. Total DNA prepared from a small portion of biopsied muscle was analyzed by Southern blot for detection of mtDNA deletions, and by PCR for point mutations at nucleotide positions 3,243 [14] and 8,344 l l5], specific to mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS), and myoclonus, epilepsy associated with RRF (MERRF), respectively, and nucleotide positions 15,923 and 15,924 [16] reported in fatal infantile mitochondriat disorders. No mtDNA mutations were detectable:

Discussion Clinically, this infant was normal at birth but underwent a progressive decline with lactic acidosis and cardiomyopathy, and died at 4 months of age. The clinical features were compatible with the fatal infantile form o f mitochondrial disorders. Although almost all patients reported with the fatal infantile mitochondrial disorder have had complex IV [1-4] or complex I deficiency [511], our patient had the decreased enzyme activities of both complexes I and IV. Cardiomyopathy has been described in both complex I and IV deficiencies with fatal infantile mitochondrial encephalomyopathy. Renal involvement revealing Fanconi

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syndrome has been observed in approximately one-half of patients with complex IV deficiency, but not in complex I deficiency. Our patient demonstrated cardiomyopathy but did not have Fanconi syndrome, suggesting that complex I deficiency is mainly responsible for his disorder. Although most patients with the fatal infantile form of complex IV deficiency have had numerous RRFs on muscle histochemistry [1-4], only 1 [11] of 5 with complex I deficiency have been reported to have RRF [5-11]. Because RRFs are recognizable in almost all patients with late-onset complex I deficiency, especially in MELAS [17], it may take time to develop RRF. A patient with the fatal infantile complex IV deficiency was reported who had no RRFs at 1 month of age but numerous RRFs 4 months later [18]. We believe that our patient is the first reported with RRFs associated with the fatal infantile form of mitochondrial disorders caused by complex I and IV deficiencies. On COX stain, all patients with the fatal infantile form of complex IV deficiency disclose no enzyme activity in muscle fibers [1-4]. This stain may be positive in fibroblasts, muscle spindles, and blood vessels revealing tissue-specific involvement in the same patient. In the 5 patients reported with the fatal infantile form of complex I deficiency, the results of the COX stain have not been well described. Our patient demonstrated mildly decreased COX activity histochemically but with no tissue specificity. There remains a possibility that the decreased COX activity is a secondarily-induced phenomenon because the patients with complex I deficiency sometimes develop focal to diffuse COX deficiency as the disease progresses [ 17]. Zheng et al. reported one patient with the fatal infantile mitochondrial disorder caused by complex I and IV deficiencies [11]. The mechanism to induce both complex 1

and IV deficiencies concomitantly remains unknown. Two enzyme defects may be induced by a single nuclear mutation affecting a common structure subunit of the two complexes or by an aberration of a nuclear oxidative phosphorylation regulating gene. Generally, a decrease in subunits of both complexes I and IV probably reflects decreased enzyme activities of both complexes. Because the biogeneses of complexes I and IV are under dual control from mitochondrial and nuclear genomes, the enzyme deficiency of both complexes can be caused by mutations in the structural genes in either of the genomes or by some disorders in the expression of the genetic information. This complexity may be responsible for the clinical heterogeneity. Because immunoblot analysis of complexes failed to reveal any specific defective subunits, we could not identify the primary enzyme defect in this patient.

We thank Dr. Nobutake Matsuo, Professor of Pediatrics, Keio University School of Medicine, for his critical reading of the manuscript.

References

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