E72.04

HCC Category Mapping

What This Code Means

An inherited disorder where cystine accumulates in cells throughout the body, particularly in the kidneys, eyes, and muscles, causing kidney failure and other complications.

Coding Tips

• •Distinguish from cystinuria (E72.01); cystinosis involves intracellular accumulation while cystinuria involves urinary loss
• •Document complications such as chronic kidney disease, corneal crystals, or muscle weakness for complete coding

Clinical Significance

Cystinosis is a rare lysosomal storage disorder caused by mutations in the CTNS gene encoding cystinosin, leading to intracellular accumulation of cystine crystals throughout the body, most notably in the kidneys, eyes, thyroid, and muscles. The infantile (nephropathic) form is most common and severe, typically causing renal Fanconi syndrome by age 1 and end-stage renal disease by age 10 without treatment. Cysteamine therapy has dramatically improved outcomes by reducing intracellular cystine levels.

Documentation Requirements

• ✓Document white blood cell cystine levels, slit lamp examination showing corneal cystine crystals, renal function including electrolytes and tubular function markers, thyroid function, CTNS gene mutation analysis, and cysteamine dosing regimen.
• ✓Record which form (infantile, juvenile, or adult) is documented.

Commonly Confused Codes