Maternally transmitted syndrome with diabetes mellitus
(DM), neurosensory deafness, and ophthalmic abnormalities.
Maternally Inherited Diabetes Mellitus-Deafness Syndrome;
Noninsulin-Dependent Diabetes Mellitus with Deafness.
Unknown. DM affects 5% of the population in the
Western world. It consists of a genetically heterogeneous group of disorders
with glucose intolerance being the common clinical feature. More than 60
different hereditary DM syndromes have been described. Maternally inherited
DM and deafness represents a unique syndrome within this grouping.
The mitochondrial form of DM and deafness is
inherited in a heterogeneous pattern. The syndrome has been associated with
a 10.4-kb mitochondrial DNA (mtDNA) deletion and a mutation in nucleotide
3243, altering the mitochondrial tRNA for leucine. The deletion is unique
because it is maternally transmitted, removes the light strand origin of
mtDNA replication, inhibits mitochondrial protein synthesis, and is not
associated with the hallmarks of other mtDNA deletion syndromes (ptosis,
ophthalmoplegia, or muscle weakness).
The mtDNA deletion causes a defect in the
mitochondrial oxidative phosphorylation, which impairs pancreatic islet cell
function. Once the mitochondrial adenosine triphosphate (ATP) production of
the islet cells falls below the level required for appropriate glucose “sensing,” DM ensues. The exact mechanism of protein synthesis inhibition
Based on clinical features consistent with the disorder
(see below). Pathologic glucose tolerance test, audiometry testing, and
ophthalmic examination. The pedigree demonstrates maternal inheritance.
The syndrome is characterized by DM (noninsulin
and insulin dependent with age of onset between 20 and 30 years),
progressive bilateral neurosensory hearing loss, and impaired vestibular
function (unsteady gait, dizziness). Ophthalmologic examination reveals
pigmentary retinal degeneration (normal visual acuity with concentric
narrowing of the visual fields) and eventually external ophthalmoplegia.
Seizures and dysarthria have also been reported.
Obtain a detailed clinical history
and a thorough clinical examination to determine the systemic involvement of
DM (coronary artery disease, arterial hypertension, nephropathy, neuropathy,
retinopathy) and the degree of hearing loss and vestibular impairment.
Review the treatment for DM (actual blood glucose level, glycemia control,
diabetic medication regimen). Evaluate cardiac function
(electrocardiography, exercise electrocardiography, echocardiogram),
neurologic function (peripheral and autonomic neuropathy), and renal
function (urea, creatinine, electrolytes, glomerular filtration rate). Blood
work should include a complete blood count.
Diabetic patients have a higher
perioperative morbidity and mortality compared to nondiabetic patients.
Diabetic patients should receive priority on all scheduled operating lists.
Perioperative monitoring of blood glucose and cardiac, pulmonary, and renal
function is essential. Meticulous attention must be paid to patient positioning
because of peripheral neuropathy, and increased propensity to tissue damage.
Patients with autonomic neuropathy are unable to compensate for
positional changes, and sympathectomy because of central neuraxial blockade
may result in severe arterial hypotension. Remember that these
patients are at increased risk for ileus and aspiration (especially patients
suffering from diabetic ketoacidosis or autonomic neuropathy with delayed
gastric emptying because of gastric atony) and require a rapid sequence
induction. Use lactate-containing solutions (lactated Ringer ...