flatbush diabetes

Last reviewed 06/2023

Ketosis prone type 2 diabetes/atypical diabetes/flatbush diabetes

• is a widespread, emerging, heterogeneous syndrome characterised by patients who present with diabetic ketoacidosis (DKA) or unprovoked ketosis with hyperglycaemia but do not necessarily have the typical phenotype of autoimmune type 1 diabetes
  • is an uncommon form of diabetes characterized by severe reversible insulin deficiency
    
    
• atypical diabetes was originally described by Banerji et al as a unique form of diabetes among African-American patients who presented with DKA as their initial manifestation of diabetes (1)
  • ketosis prone type 2 diabetes, though first described and mostly observed in males of African-American descent, has been identified in Asian populations, including Japanese and Chinese
    • there is an increased male preponderance in this condition
      
      
  • in a South African study, half the presentations of DKA were due to type 2 diabetes (2)
    
    
  • at initial presentation, the patients with type 2 diabetes and DKA cannot be reliably separated from those with type 1 diabetes; however, they tend to be middle-aged, obese, hypertensive and may have markers of insulin resistance such as acanthosis nigricans (2)
    • often a positive family history of type 2 diabetes
    • mechanism underlying their presentation seems to be the combination of insensitivity to insulin and transient loss of ability to release adequate amounts of insulin
      
      
  • in contrast to type 1 diabetes, patients with atypical diabetes undergo spontaneous remission and maintain long-term insulin independence (1,3)
    • during admission the patients with type 2 diabetes gradually lose their insulin resistance
    • patients with ketosis prone type 2 diabetes do not have the autoantibodies associated with type 1 diabetes and they have recovery of insulin secretion as evidenced by rising levels of C peptide
    • at presentation, they have impairment of both insulin secretion and insulin action
      • intensified diabetes management results in significant improvement in ß-cell function and insulin sensitivity to allow gradual discontinuation of insulin therapy

Because of mixed features of type 1 diabetes and type 2 diabetes, this variant has been given several names including atypical diabetes, diabetes mellitus type 1b, idiopathic type1 diabetes, Flatbush diabetes mellitus, type 1.5 diabetes mellitus and ketosis-prone type 2 diabetes mellitus.

Reference:

• Banerji MA, Chaiken RL, Huey H, et al. GAD antibody negative NIDDM in adult black subjects with diabetic ketoacidosis and increased frequency of human leukocyte antigen DR3 and DR4: Flatbush diabetes. Diabetes 1994;43:741-5.
• Howarth D. Ketoacidosis in a patient with type 2 diabetes - flatbush diabetes.Aust Fam Physician. 2015 Jan-Feb;44(1-2):53-4.
• Umpierrez GE, Casals MM, Gebhart SP, et al. Diabetic ketoacidosis in obese African-Americans. Diabetes 1995;44:790-5