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When to Suspect Cystic Fibrosis in Patients with Diabetes

Two cases studies of CF males who went undiagnosed until infertility was presented…

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CF is caused by a defect in the CFTR gene, which results in a progressive lung disease, pancreatic dysfunction, elevated sweat chloride, and male infertility. Generally, CF affects multiple organ systems in varying degrees, but atypical CF could involve only one organ system that develops later on in adolescent and adulthood. This article describes two case studies in which two young men with diabetes, presenting with infertility, led to the diagnosis of CF.

Patient 1 was a 32 y.o. male with diabetes. The patient presented with initially a high FPG and PPG, with normal testosterone, LH, FSH, liver, pancreas, and kidneys; and his diabetes was managed with metformin and glipizide. The patient consulted the authors on infertility issues and when presented was found to be azoospermia with a suggestion of distal duct obstruction; therefore, a transrectal ultrasound (TRUS) was performed. CF diagnosis was suggested after the TRUS results, and the authors confirmed it with a sweat chloride test. Patient 1 had a chloride level of >60 mEq/L on two occasions.

Patient 2 was a 27 y.o. non-obese male who consulted the authors due to primary infertility. He has been diagnosed with diabetes in the past and his blood glucose was under control with gliclazide and metformin. His hormones levels were normal, but his seminal fluid analyses showed low ejaculation volume, low pH, and azoospermia. A TRUS test and sweat chloride test was subsequently performed and his sweat chloride levels were >60 mEq/L on two occasions.

Atypical CF poses a significant diagnostic challenge due to its milder form, with signs and symptoms of CF not showing till much later in adolescence or adulthood. The patients in this study had CF-related diabetes (CFRD) and it was only diagnosed when the two patients consulted the authors for infertility. Early CFRD diagnosis is important due to complication association with CFRD compared to CF patients without diabetes: infections, pulmonary function decline, weight loss, growth impairment, microvascular complications, and rates of higher mortality; however, diabetes in CF is generally asymptomatic and difficult to detect, and the only current therapy for CFRD is insulin and oral diabetic medications are not recommended.

Subtle signs and symptoms of respiratory, gastrointestinal, endocrine, metabolic, and genitourinary dysfunction should alert physicians of the possibility of CF; and not all non-insulin requiring diabetics have T2D. In these two cases, both patients had diabetes and primary infertility that later on was discovered to be CF. Physicians should consider the possibility of CFRD in diabetic patients and all CF patients should be tested early on for CFRD with an oral glucose tolerance test.

Practice Pearls:

  • Two different case studies of males presenting with both diabetes and primary infertility; both patients were later diagnosed with CFRD.
  • Physicians should be aware of the subtle signs and symptoms of CF, and all CF patients should be tested for CFRD with an oral glucose tolerance test.
  • Early detection will aid in the selecting the optimal therapy for CFRD and prevent progressing complications; current therapy recommendation for CFRD is insulin, and oral diabetic medications are not recommended.

Chakraborty PP, Ray S, Bhattacharjee R, Ghosh S, and et al. Diabetes and Primary Infertility in Young Males: Do not Forget Cystic Fibrosis. Clinical Diabetes. 2015; 33(2): 80-83.