flatbush diabetes

Last reviewed 05/2022

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.