A 6 month old with severe metabolic acidosis

Dr  Ira Shah

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A 6 month old with severe metabolic acidosis

Dr Ira Shah.

Medical Sciences Department, Pediatric Oncall, Mumbai, India.

ADDRESS FOR CORRESPONDENCE
Dr Ira Shah, Medical Sciences Department, Pediatric Oncall, 1, B Saguna, 271, B St. Francis Road, Vile Parle {W}, Mumbai 400056.

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Clinical Problem
A 6-month-old girl born of third degree consanguineous marriage was referred for further management. At 5 months of age, she was hospitalized with fever and breathlessness since 2 days. She was found to have severe metabolic acidosis (pH = 6.9, Hco3 = 3.7mEq/L) and in shock. She was given bicarbonate infusions, intubated and required ventilatory support for 4 days. Her septic workup was negative. Her electrolytes showed hypokalemia (Serum potassium = 2.8Meq/L) with serum sodium of 135 meq/L and chloride of 95 meq/L. On further inquiry she was found to have polyuria and polydipsia along with delayed milestones. (She had achieved partial head holding and social smile at 4 months). A urine analysis revealed phosphaturia and 1+ albuminuria. She was suspected as a case of Proximal Renal Tubular acidosis with Lowe’s syndrome in view of mental retardation and treated with bicarbonate supplements. A urinary aminoacidogram for Proximal RTA showed fructosuria. However, following this episode she had lost all her milestones and thus was referred for further management.

What is the diagnosis in this child?

Discussion
Dr Ira Shah: If one clearly evaluates the history, one can summarize that the child had delayed development to begin with and there is complete loss of milestones following a febrile episode. Thus, the child has neuroregressed. Also infective etiology seems to be unlikely as the septic workup was negative. Thus one would suspect a metabolic disorder.

The primary physician diagnosed RTA on the basis of polyuria, polydipsia, metabolic acidosis and hypokalemia. However, one basic principle that needs to be followed was “ANION GAP”. In RTA, the anion gap would be normal whereas in an inborn error of metabolism (IEM) (organic acidemias, lactic acidosis, fatty acid oxidation defect), the anion gap would be high as was found in this case. Also one should not rely on the subjective history of polyuria and polydipsia at this age and objectively collect 24 hours urine and check whether it is really polyuric.
This child had a high anion gap metabolic acidosis making one suspect an IEM. An MRI brain revealed mitochondrial encephalopathy and urine chromatography was showing lactic aciduria. Serum and CSF lactate were both high. Serum ammonia was normal. The child was started on Thiamine, Riboflavin supplements and the acidosis is now under control.

Thus, one can conclude that basics of ANION GAP and metabolic acidosis would aid in coming to a diagnosis rather than going for high tech investigations that would only confuse the picture further.

Compliance with ethical standards

Funding: None

Conflict of Interest: None

Cite this article as:
Shah I. A 6 month old with severe metabolic acidosis. Pediatr Oncall J. 2005;3: 50.