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Let's go on to a case. Here we have an otherwise healthy 9-year-old girl who is brought to the
emergency room by her father because of excessive thirst, frequent urination, and significant
weight loss. His symptoms started acutely 5 days ago. Vital signs reveal a temperature of 36.6°C,
a blood pressure of 100/65, and a pulse rate of 105 beats/minute. Physical examination shows a thin
girl with dry mucous membranes and eyes that appear sunken in her orbits. Labs reveal a random
blood glucose of 410, a C-peptide level that is undetectable, and a serum beta-hydroxybutyrate
level that is negative. What is the most likely diagnosis? Looking at this case, one first notices
the age of the patient; a 9-year-old girl who comes in with what seems like the classic symptoms of
diabetes. She has excessive thirst and frequent urination that is also now associated with significant
weight loss and is more likely to manifest with type 1 diabetes. The classic symptoms of
hypoglycemia, polyuria, and polydipsia are present here in association with weight loss. The
elevated glucose is caused by insulin deficiency. This leads to increased glucose in the urine and
her urine volume, which is called an osmotic diuresis. She has volume loss or excessive urination
from the body and this leads to dehydration and works in her symptoms more acutely. Her heart
rate is elevated and her mucous membranes are dry and her eyes appear sunken. These are examination
features that bring into the conclusion that this patient has dehydration, probably a combination of
reduced oral intake combined with increased urine output. She suffers from a lack of insulin and she
is breaking down protein stores to generate energy which leads to the reduction in her body mass
index and causes her drop in weight. She has a clinical manifestation of dehydration or volume loss
as evidenced by dry mucous membranes, tachycardia, and reduced skin turgor, as well as a lower
blood pressure. When one sees this manifestation of eyes that appear sunken in the orbits, it
generally implies clinically that the dehydration is more advanced than one would encounter without
this manifestation. As you can see from her labs, her serum glucose is markedly elevated at
410mg/dL. As you know from the normal ranges, this exceeds a random plasma glucose of greater than
or equal to 200 mg/dL and will clinch the diagnosis of type 1 diabetes in this patient. The C-peptide
is undetectable and usually a low C-peptide indicates that there is a lack of endogenous insulin
secretion. The sort of thing that you would expect in a patient who has type 1 diabetes which is
also induced by autoimmune destruction of the pancreatic islet cells. The patient has a negative
serum beta-hydroxybutyrate level. This is a ketone body and the fact that it is negative suggests
that she does not have a ketoacidosis on top of her nearly-diagnosed type 1 diabetes. So, our
conclusion here in this case is that the most likely diagnosis for this girl is that it is newly-diagnosed
type 1 diabetes. She has clinical signs of diabetes with a random serum glucose greater than or
equal to 200 and classic symptoms. She is also presenting dehydrated. The C-peptide, which is
undetectable, implies that there is decreased insulin secretion endogenously and the fact that her
serum beta-hydroxybutyrate level is negative implies that she does not have a ketoacidosis.