Neonatal Lethargy and Hypotonia; Enzyme Deficiency! - USMLE Forums
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  #1  
Old 12-19-2011
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Kids Neonatal Lethargy and Hypotonia; Enzyme Deficiency!

A three-and-a-half-week-old infant is brought to the pediatrician by her parents for progressively increasing lethargy. The child was born via normal vaginal delivery without complication. During the first week of life, no abnormalities were noted. Thereafter, the child started to feed poorly and regurgitate food contents on occasion. On exam, vital signs are: temperature 36.6° C, pulse 110/min, respirations 32/min, blood pressure 98/65 mmHg. The patient has a high forehead with a broad nasal bridge. The philtrum is smooth. A white film is present on the patient’s tongue consistent with oral candidiasis. No murmurs are appreciated on cardiac auscultation. No wheezes or rhonchi are heard on pulmonary exam. Abdominal exam reveals mild hepatomegaly. Pervasive hypotonia of the upper and lower extremities is present. Mass spectrometry is performed on a urine sample and elevated levels of methylcitrate and propionic acid are detected. Methylmalonic acid levels are also noted to be increased.
The deficient enzyme is in this disease is directly responsible for the production of which of the following products?

A. Methylmalonyl-CoA mutase

B. Methylmalonyl-CoA
C. Succinyl-CoA
D. Pyruvate
E. Acyl-CoA*
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Old 12-19-2011
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succinyl coA
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succinyl CoA... this is methylmalonyl CoA mutase deficiency
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the answer is c
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Metabolism of 4 amino acids Methionine, Isoleucine,Valine, Threonine,
and odd-chain fatty acids all proceed via propionyl-CoA. Propionyl-CoA is
metabolized ultimately to succinyl-CoA that enters the citric acid cycle, which produces usable energy for the cell.
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Old 12-19-2011
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C). succinyl co-a

isnt this a biochemistry que for step1 rather then ck?
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answer is succinyl CoA . The famous VOMIT pathway!!
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Quote:
Originally Posted by rise View Post
answer is succinyl CoA . The famous VOMIT pathway!!
C. Succinyl-CoA
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The correct answer is C. Succinyl-CoA.
This patient is most likely experiencing methylmalonic acidemia. This form of acidemia occurs in approximately 1 per 50,000 births and is often the result of a methylmalonyl-CoA mutase (MCM) deficiency. This enzyme is normally involved in converting methylmalonyl-CoA to succinyl-CoA. However, given that MCM is adenosylcobalamindependent, many other biochemical abnormalities besides MCM deficiency can result in methylmalonic acidemia, including dietary cobalamin and intrinsic factor deficiencies. In fact, methylmalonic acidemia comprises seven different disease types. Regardless of the etiology, the end result is the same: accumulation of methylmalonic acid and consequent methylmalonic acidemia. Pyruvate is a product of glycolysis and is derived from phosphoenolpyruvate (PEP). Acyl CoA is derived from long chain fatty acids in a reaction catalyzed by acetyl CoA. Children with methylmalonic acidemia are usually asymptomatic during the initial 1 to 2 weeks after birth. Subsequently, they then begin to exhibit symptoms including lethargy, poor feeding, failure to thrive, and hypotonia. Decreased glomerular filtration rate, retinopathy, and hydrocephalus have all been documented to occur in this patient population. Facial dysmor-phisms, hepatomegaly, oral thrush, dehydration, and hypotonia are other features that can be seen in methylmalonic acidemia. Diagnosis can be confirmed using gas-liquid chromatography and mass spectrometry to detect elevated levels of methylmalonic acid in body fluids (serum, urine, CSF).Patients with methylmalonic acidemia are at increased risk for metabolic decompensation during high catabolic states (e.g., infection, stress, surgery). In these situations, protein intakeshould initially be decreased to prevent further exacerbation of symptoms. Methylmalonyl-CoA is derived from amino acids such as isoleucine, valine, and methionine in addition to other progenitor molecules, and limiting protein intakehelps mitigate methylmalonyl-CoA accumulation and disease exacerbation. In addition to a low-protein diet, patients also receive carnitine and possibly cobalamin supplementation. Liver or kidney transplantation may also be helpful in some patients.
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