This woman has long-standing uncontrolled type 2 diabetes. Both cataracts (Figure A) and peripheral neuropathy are caused by accumulation of sorbitol resulting from elevated glucose.
Via the polyol pathway, the enzyme aldose reductase converts glucose into sorbitol, which accumulates in the lens of the eye causing osmotic stress that leads to cataract formation. Similarly, osmotic stress due to sorbitol accumulation damages peripheral nerves, leading to diabetic neuropathy. Reactive oxygen species and excess glycolysis leading to mitochondrial dysfunction are also thought to contribute to neuropathy.
Rosenberg and Sperazza discuss management of patients with vision loss. The top four causes of vision loss in the US are age-related macular degeneration, cataracts (due to all etiologies, not solely diabetes), glaucoma, and diabetic retinopathy. Diabetic retinopathy is another microvascular complication of diabetes that responds to tight glucose control.
Callaghan et al. review manifestations of diabetic peripheral neuropathy. Prevalence of neuropathy in diabetics is about 30%, most commonly distal symmetric polyneuropathy. The best treatment for neuropathy is glucose control (more effective in type I than type II diabetes) and pain management.
Figure A shows lens opacification seen in diabetes-related cataracts.
Illustration A, from Callaghan, shows the many potential mechanisms of cell damage in both type I and type II diabetes.
Illustration B lists micro- and macrovascular complications of diabetes.
Answer 1: This describes acanthosis nigricans, a skin finding associated with insulin resistance in type 2 diabetes that is thought to be caused by insulin-mediated effects on fibroblasts and keratinocytes to stimulate their proliferation.
Answer 3: This describes rhinocerebral mucormycosis, a fungal infection more common in diabetic patients, especially those in DKA. Relative immunosuppression and ketosis are factors that allow Rhizopus to grow unchecked, especially since it possesses ketone reductase allowing it to grow in the acidic, glucose rich state of DKA.
Answer 4: Intermittent claudication is a symptom of peripheral vascular disease, a macrovascular complication of diabetes resulting from atherosclerosis and endothelial cell dysfunction.
Answer 5: Diabetic foot ulcers result from a combination of factors, including peripheral neuropathy (Answer 2) but also impaired wound healing, peripheral vascular disease and repetitive trauma to the insensate foot.
Rosenberg EA, Sperazza LC. The visually impaired patient. Am Fam Physician. 2008 May 15;77(10):1431-6. Review. PubMed PMID: 18533377
PMID:18533377 (Link to Abstract)
Callaghan BC, Cheng HT, Stables CL, Smith AL, Feldman EL. Diabetic neuropathy: clinical manifestations and current treatments. Lancet Neurol. 2012 Jun;11(6):521-34. doi: 10.1016/S1474-4422(12)70065-0. Epub 2012 May 16. Review. PubMed PMID: 22608666
PMID: 22608666 (Link to Abstract)