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Christine Ahn MD
Carl Allen DDS, MSD
Brandon Ayres MD
Howard P. Baden MD
Robert Baran MD
Keira Barr MD
Gregory J. Basura MD, Ph.D
Donald Belsito MD
Jeffrey D. Bernhard MD
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Sarah Brenner MD
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Walter Brooks MD
William Buckley MD
Philip Bulterys MD, PhD (candidate)
Susan Burgin MD
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Sean P. Bush MD, FACEP
Jeffrey Callen MD
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Michael Cardwell
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Robert Chalmers MD, MRCP, FRCP
Chia-Yu Chu MD, PhD
Flavio Ciferri MD
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Noah Craft MD, PhD
John T. Crissey MD
Harold E. Cross MD, PhD
Charles E. Crutchfield III MD
Adriana Cruz MD
Donna Culton MD, PhD
Bart J. Currie MBBS, FRACP, DTM&H
Chicky Dadlani MD
Alexander Dane DO
C. Ralph Daniel III MD
Thomas Darling MD, PhD
William Delaney MD
Damian P. DiCostanzo MD
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James Earls MD
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Melissa K. Egge MD
Charles N. Ellis MD
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Organizations
Am. Journal of Trop. Med & Hygiene
Armed Forces Pest Management Board
Blackwell Publishing
Bugwood Network
Centers For Disease Control and Prevention
Centro Internacional de Entrenamiento e Investigaciones Mèdicas (CIDEIM)
Dermatology Online Journal
East Carolina University (ECU), Division of Dermatology
Contributors: Harold E. Cross MD, PhD, Jeffrey D. Bernhard MD, Brandon D. Ayres MD, Christopher Rapuano MD, Harvey A. Brown MD, Sunir J. Garg MD, Lauren Patty Daskivich MD, MSHS
Eye
Cystinosis is a clinically heterogeneous disorder with widespread organ damage resulting from tissue accumulation of cystine crystals. The most serious damage occurs in the kidney and may result in end-stage disease. However, other organs such as the thyroid and pancreas are often damaged as well.
Mutations in the CTNS gene are responsible for all cases of cystinosis, even though there can be considerable heterogeneity in clinical presentation. Individuals are generally grouped into 1 of 3 categories of disease. The most common and severe form is known as infantile or nephropathic cystinosis. These patients may have Fanconi-type renal tubular disease at an age as early as 6 months, and some patients require a renal transplant in the first decade of life. Poor feeding with failure to thrive are also evident in the first year of life. Retarded physical growth in the range of 50% of normal is evident in the same period. Hypophosphatemic rickets may be a consequence of untreated renal disease. Cystine crystals may be seen in the cornea at this time as well, and their presence causes significant sensitivity to light (photophobia). The retinal photoreceptors are damaged early, and patients may experience significant loss of vision as youngsters. Retinal pigment clumping and areas of hypopigmentation occur in the fundus periphery and progress centrally.
Intermediate or juvenile cystinosis is far less common, and the onset of clinical manifestations is often delayed until the second decade of life. Nephropathy is usually present but may be so mild that it can remain undetected until late stages. Electrolyte imbalance, growth retardation, and ocular symptoms may also escape detection for a decade or more. However, renal failure always occurs, usually by the third decade of life. These patients also have corneal crystals and photophobia and sometimes experience painful recurrent corneal erosions. Photoreceptor damage leading to vision loss is common. The pigmentary changes in the retina are similar to those in the infantile form of the disease.
Some individuals do not develop renal damage and have photophobia as their only symptom. This form of cystinosis is sometimes called ocular, non-nephropathic, or adult disease. Patients with this form of disease do not suffer photoreceptor damage or have retinal pigmentary changes. Corneal crystals cause photophobia, which may be the only symptom. Recurrent corneal erosions often occur.
Individuals with early-onset disease who survive into the third decade of life or later may develop late abnormalities such as myopathy, gastrointestinal dysfunction, cardiovascular disease, and central nervous system damage.
For more information on the infantile form, see OMIM.
For more information on the intermediate form, see OMIM.
For more information on the adult-onset form, see OMIM.
Codes
ICD10CM: E72.04 – Cystinosis
SNOMEDCT: 190681003 – Cystinosis
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Differential Diagnosis & Pitfalls
Other causes of Fanconi syndrome such as Lowe oculocerebrorenal syndrome and Pearson marrow-pancreas syndrome can be ruled out by examination of the cornea.
There are many developmental disorders in which failure to thrive and difficulty feeding are part of the clinical spectrum, but most have other malformations or systemic signs that are not characteristic of cystinosis.
Disorders of carbohydrate metabolism such as galactosemia and glycogen storage disease may be associated with failure to thrive and feeding difficulties.
