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Normal pressure glaucoma (NPG) can be associated with numerous vascular risk factors including previous major blood loss, diabetes, hypertension, carotid stenosis, head injury, migraine and chronic Valsalva manoeuvres.1,2 We report a patient with carnitine palmitoyl transferase II deficiency (CPTIID) who sustained major haemodynamic stress and demonstrated progression of NPG.

Case Description

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  2. Case Description
  3. Comment
  4. References

A 48-year-old white male presented in 2003 to discuss contact lens use. In 1998 he had required three coronary stents following a myocardial infarction related to heavy exertion.

CPTIID had been diagnosed at the age of 21 during hospitalization in New York following strenuous exertion. During this episode his legs became swollen and immobile. Muscle biopsy demonstrated features consistent with CPTIID. In retrospect, he had had several similar episodes from the age of 18.

His visual acuity (VA) was 6/4. He had open angles, Shaffer grade four, with intraocular pressures (IOPs) of 8 mmHg right eye (OD) and 7 mmHg left eye (OS). Humphrey static automated perimetry (SAP) 24-2 was normal both eyes OU. The optic nerve cup-to-disc ratio (CDR) was 0.9 OD and 0.85 OS, with an early notch in the left neuroretinal rim superiorly. He was considered an NPG suspect and asked to return in 6 months.

At his next review, not until 2009, he reported an episode of life-threatening rhabdomyolysis in 2006 due to CPTIID. This occurred during mountain climbing in an isolated location in New Zealand. He was unable to be medically evacuated promptly, and progressive rhabdomyolysis led to cardiac arrest, with extreme hypotension over 12 h. Cardiac output was absent for 11 min. Following medical retrieval, he was managed in ICU for cardiogenic shock and acute renal failure. He required intubation, inotropic support and haemodialysis. Bilateral fasciotomies for calf compartment syndrome were done, followed by tendon reconstruction (Fig. 1).

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Figure 1. (a) Anterior view of both legs of patient demonstrating marked tissue loss. (b) Lateral view of patient's left leg demonstrating scar, following fasciotomies, 4 years postoperatively.

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His VA remained at 6/4 OU, with IOPs of 16 mmHg OD and 14 mmHg OS. SAP revealed a large temporal scotoma, with superior and inferior arcuate scotomas OD, and a large inferior arcuate scotoma OS. The CDR OD remained at 0.9, but with a temporal notch; the CDR OS had increased to 0.95. GDx computerized retinal nerve fibre layer analysis revealed marked abnormalities bilaterally. Bilateral neuroretinal rim thinning had now developed inferiorly. A topical prostaglandin analogue was commenced.

Comment

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  2. Case Description
  3. Comment
  4. References

CPTIID may represent another risk factor for progression of NPG. Indeed, the complications of CPTIID in this patient suggest a significant temporal association with the progression of his suspected NPG.

CPTIID, an autosomal recessive disorder, may present perinatally in infants or in adulthood.3 It is associated with the CPT system of mitochondria, involved in fatty acid oxidation4 (Fig. 2). The most common mutation of CPT II is S113L in adults.5 The most accepted pathophysiological theory is that lipid accumulation in muscle during exercise cannot be metabolized, resulting in rhabdomyolysis.3,5

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Figure 2. Summary of carnitine pathway. Following passage of fatty acids and carnitine through the plasma membrane into the cell cytoplasm, CPTI facilitates their passage through the outer mitochondrial membrane. CPTII facilitates their passage into mitochondrial cytoplasm, through the inner mitochondrial membrane, where they are utilized for beta-oxidation. CACT, Carnitine-acylcarnitine translocase; CPTI, Carnitine palmitoyltransferase I; CPTII, Carnitine palmitoyltransferase II.

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In adults, CPTIID is usually benign, only being expressed during strenuous exercise.3,5 Rhabdomyolysis can then result in severe hypotension and renal failure.5 The protracted hypotension in our patient may have contributed to the optic nerve, SAP and GDx changes. To have demonstrated a definitive temporal association, immediate pre-morbid and post-morbid NPG assessment would have been required, unfortunately, it was not possible because of the patient's non-attendance.

This case report suggests the benefit of evaluating NPG with a directed history of strenuous exercise in the context of possible CPTIID.

References

  1. Top of page
  2. Case Description
  3. Comment
  4. References