Illness Scripts

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An illness script is a structured mental summary of a doctor's knowledge about a specific disease. It represents a their knowledge about a particular disease, and may be as short as a paragraph for a rare disease, or as long as a book chapter for a commonly encountered illness. Classically, the components of a thorough illness script fall into three main categories:

Risk factors for the disease
Pathophysiology
Clinical characteristics.

Within these categories, illness scripts often include a disease's pathophysiology, epidemiology, time course, salient symptoms and signs, diagnostics, and treatment. For example, a provider’s illness script for lateral femoral cutaneous nerve entrapment (LFCNE) may include:

Illness Script Example: Lateral Femoral Cutaneous Nerve Entrapment
Pathophysiology	Entrapment of the lateral femoral cutaneous nerve
Epidemiology	3.4–4.3/10,000 person-years It is significantly linked to carpal tunnel syndrome, pregnancy, obesity, and diabetes mellitus
Time course	Chronic
Salient Symptoms and Signs	Pain and/or dysaesthesia, and sensory changes without motor findings, in the distribution of the lateral femoral cutaneous nerve.
Diagnostics	Usually clinical diagnosis. Diagnostic injection and MRI can corroborate the diagnosis.
Treatment	Conservative management, injection, hydro-dissection.

With experience, providers hone their illness scripts in three important ways:

They encode a predictive value for each feature of the disease, enabling them to estimate the likelihood of a diagnosis when that feature is present or absent. Example: The absence of a pain does not exclude the diagnosis of LFCNE.
They emphasize distinguishing characteristics whose presence or absence significantly alters the likelihood of the diagnosis, and helps differentiate it from another related diagnosis. Example: symptoms occurring in a well circumscribed area in the distribution of the lateral femoral cutaneous nerve highly suggestive of LFCNE and makes lumbar radicular pain causes less likely.
They develop a list of disease mimickers to consider when an illness script of a particular diagnosis is invoked. Example: L2 or L3 radiculopathy, pelvic mass, superior gluteal nerve entrapment, hip joint pain, inguinal hernia, GTPS, femoral neuropathy.

This iterative process continued throughout a clinician’s career, adds depth, precision and differentiating power to the foundational scripts developed during training. Diseases encountered less frequently will have less robust scripts.

The key to diagnosis lies in appropriately selecting which details to commit to memory.

“The skillful workman is very careful indeed as to what he takes into his brain-attic”
—Sherlock Holmes, A Study in Scarlet

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Part or all of this article or section is derived from Illness Scripts Overview by JGIM, used under CC-BY-NC-SA