Case Presentation: Frequent monitoring of capillary blood glucose values is common practice in the hospital setting. In most healthy adults, capillary blood glucose values correlate well with venous blood glucose values. However, in some cases there may be a discrepancy between the two and can result in pseudo hypoglycemia, where an asymptomatic patient has spuriously low capillary blood glucose values. We present two cases of pseudo hypoglycemia due to underlying Raynaud’s phenomenon. Case 1. 61-year-old female with known history of Scleroderma and Raynaud’s phenomenon (with positive ANA, Rheumatoid factor, SS-A and SS-B) status post double lung transplant, history of esophageal dysmotility and history of recurrent pneumonia presented to our facility with hypercapnic respiratory failure. Exam was notable for cool hands, intact radial pulses, thickening and tightening of the skin of the face, fingers and hands. During hospital admission, patient was noted to have recurrent hypoglycemic episodes on finger stick glucose (as low as 29 mg/dl) that did not correlate with simultaneous venous sampling (179 mg/dl). Patient did not have any changes from her baseline neurological status during these episodes. After multiple data points demonstrating disparity between fingerstick and venous blood glucose, the patient was thought to have pseudo hypoglycemia due to underlying Raynaud’s phenomenon.
Case 2. 72-year-old female with past medical history of diabetes mellitus on metformin, presented to the hospital for recurrent syncopal episodes. Patient denied headaches, seizure like symptoms, focal neurological deficits, chest pain or dyspnea. She did endorse diffuse joint pain as well as dry eyes, dry mouth and skin tightening of her fingers. Skin exam revealed telangiectasias on palms and swelling, skin tightening and bluish discoloration of the fingers. Upon diagnostic evaluation, patient was noted to have recurrent hypoglycemic episodes on finger stick glucose (as low as 40 mg/dl), but without concurrent drop in venous blood glucose or hypoglycemic symptoms. Clinically, patient did not fulfill Whipple’s’ triad and extensive laboratory evaluation including cortisol, proinsulin, insulin, glucagon, c-peptide, sulfonylurea screen, insulin like growth factors, growth hormone and serum ketones did not indicate pituitary or pancreatic pathology. Additionally, complete immunological work up identified positive SS-A antibody, clinically suggestive of Crest syndrome. Her episodes of recurrent fingerstick hypoglycemia were likely due to impairment of the microvasculature of the fingers from Raynaud’s.
Discussion: The above cases stress the importance of investigating underlying etiologies of pseudo hypoglycemia including impaired capillary blood flow (ie: circulatory shock, hypothermia, vascular disease), increased glycolysis (ie: polycythemia vera) and hyperviscosity syndromes. In the two patients discussed, the discrepancy between capillary blood glucose and venous blood glucose is thought to be due to reduction of capillary blood flow, leading to slowing of glucose transport and subsequent increased uptake of glucose by local tissues.
Conclusions: In conclusion, clinicians should be mindful of the limitations of finger stick glucose measurements in asymptomatic patients with suspected impaired microcirculation. In these patients, capillary blood glucose monitoring should be confirmed with simultaneous venous sampling before initiating unnecessary and costly work up.
