We would like to report follow-up on our former patient with corneal crystals, myopathy, and nephropathy,1 and some recent communication regarding the diagnosis of corneal crystals.
Our patient moved to another city and was followed by the neurological service of a well-known pediatric hospital. Their evaluation and our communication with them did not yield a definite diagnosis (cystinosis or otherwise). The patient had persistent difficulty swallowing, developed oxygen desaturation especially at night, and died of respiratory insufficiency at age 18. An autopsy was not permitted.
In our report we stated that "White blood cell cystine was decreased (1.5 pmol/gm protein)."1 This prompted communication from the Acting Chief of the Human Genetics Branch of the National Institute of Child Health and Human Development, William A. Gahl, MD, PhD. Dr Gahl has observed a spectrum of presentations of cystinosis, noting that the corneal crystals are consistently hexagonal. He had observed patients with myopathy and elevated leukocyte cystine and expressed concern about our value of cystine concentration. Therefore, James D. Jones, PhD, a Mayo Clinical Chemist, responded. Leukocyte cystine was measured by ion-exchange chromatography. The sensitivity of this technique is sufficient to detect the homozygous, but not the normal, cystine level. Our value was less than 0.9 pmol cystine .5 gm protein.
Brooks et al have described a technique for accurate viewing of corneal crystals in vivo by specular microscopy2; we wish it could have been performed on our patient.
Our patient had corneal crystals as early as age 8 and first evidence of myopathy and nephropathy before age 13. She never had evidence of renal tubular dysfunction. Her white blood cell cystine was not elevated, and we still do not have sufficient evidence to make a diagnosis of cystinosis.
1. Arnold RW, Stickler GB, Bourne WM, et al: Corneal crystals, myopathy and nephropathy: A new syndrome? J Pediatr Ophthalmol Strabismus 1987; 24:151-154.
2. Brooks AMV, Grant G, Gillies WE: Determination of the nature of corneal crystals by specular microscopy. Ophthalmology 1988; 95:448-452.