Glycogen storage disease type II diagnostic study of choice

Glycogen storage disease type II Microchapters
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief:

Overview

• The page name should be "[Disease name] diagnostic study of choice", with only the first letter of the title capitalized. Note that the page is called "Diagnostic study of choice."
• Goal:
  • To describe the most efficient/sensitive/specific test that is utilized for diagnosis of [disease name].
  • To describe the gold standard test for the diagnosis of [disease name].
  • To describe the diagnostic criteria, which may be based on clinical findings, physical exam signs, pathological findings, lab findings, findings on imaging, or even findings that exclude other diseases.
• As with all microchapter pages linking to the main page, at the top of the edit box put {{CMG}}, your name template, and the microchapter navigation template you created at the beginning.
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• Remember to follow the same format and capitalization of letters as outlined in the template below.
• You should include the name of the disease in the first sentence of every subsection.

Diagnostic Study of Choice

Gold standard/Study of choice:

• [Name of the investigation] is the gold standard test for the diagnosis of [disease name].
• The following result of [gold standard test] is confirmatory of [disease name]:
  • Result 1
  • Result 2
• The [name of investigation] should be performed when:
  • The patient presented with symptoms/signs 1. 2, 3.
  • A positive [test] is detected in the patient.
• [Name of the investigation] is the gold standard test for the diagnosis of [disease name].
• The diagnostic study of choice for [disease name] is [name of investigation].
• There is no single diagnostic study of choice for the diagnosis of [disease name].
• There is no single diagnostic study of choice for the diagnosis of [disease name], but [disease name] can be diagnosed based on [name of the investigation 1] and [name of the investigation 2].
• [Disease name] is mainly diagnosed based on clinical presentation.
• Investigations:
  • Among patients who present with clinical signs of [disease name], the [investigation name] is the most specific test for the diagnosis.
  • Among patients who present with clinical signs of [disease name], the [investigation name] is the most sensitive test for diagnosis.
  • Among patients who present with clinical signs of [disease name], the [investigation name] is the most efficient test for diagnosis.

The comparison table for diagnostic studies of choice for [disease name]

	Sensitivity	Specificity
Test 1	✔	...%
Test 2	...%	✔

✔= The best test based on the feature

Diagnostic results

The following result of [investigation name] is confirmatory of [disease name]:

• Result 1
• Result 2

Sequence of Diagnostic Studies

The [name of investigation] should be performed when:

• The patient presented with symptoms/signs 1, 2, and 3 as the first step of diagnosis.
• A positive [test] is detected in the patient, to confirm the diagnosis.

Diagnostic Criteria

• Here you should describe the details of the diagnostic criteria.
• Always mention the name of the criteria/definition you are about to list (e.g. modified Duke criteria for diagnosis of endocarditis / 3rd universal definition of MI) and cite the primary source of where this criteria/definition is found.
• Although not necessary, it is recommended that you include the criteria in a table. Make sure you always cite the source of the content and whether the table has been adapted from another source.
• Be very clear as to the number of criteria (or threshold) that needs to be met out of the total number of criteria.
• Distinguish criteria based on their nature (e.g. clinical criteria / pathological criteria/ imaging criteria) before discussing them in details.
• To view an example (endocarditis diagnostic criteria), click here
• If relevant, add additional information that might help the reader distinguish various criteria or the evolution of criteria (e.g. original criteria vs. modified criteria).
• You may also add information about the sensitivity and specificity of the criteria, the pre-test probability, and other figures that may help the reader understand how valuable the criteria are clinically.
• [Disease name] is mainly diagnosed based on clinical presentation. There are no established criteria for the diagnosis of [disease name].
• There is no single diagnostic study of choice for [disease name], though [disease name] may be diagnosed based on [name of criteria] established by [...].

• The diagnosis of [disease name] is made when at least [number] of the following [number] diagnostic criteria are met: [criterion 1], [criterion 2], [criterion 3], and [criterion 4].
• The diagnosis of [disease name] is based on the [criteria name] criteria, which includes [criterion 1], [criterion 2], and [criterion 3].

• [Disease name] may be diagnosed at any time if one or more of the following criteria are met:
  • Criteria 1
  • Criteria 2
  • Criteria 3

IF there are clear, established diagnostic criteria:

• The diagnosis of [disease name] is made when at least [number] of the following [number] diagnostic criteria are met: [criterion 1], [criterion 2], [criterion 3], and [criterion 4].
• The diagnosis of [disease name] is based on the [criteria name] criteria, which include [criterion 1], [criterion 2], and [criterion 3].
• The diagnosis of [disease name] is based on the [definition name] definition, which includes [criterion 1], [criterion 2], and [criterion 3].

IF there are no established diagnostic criteria: 

• There are no established criteria for the diagnosis of [disease name].

Diagnostic algorithm for Infantile onset glyogen storage disease type II
COMMON PRESENTING SYMPTOMS	CARDIOVASCULAR Cardiomegaly; Congestive heart failure; Arrhythmias such as supraventricular tachycardia; Cardiac arrest during surgery.   PULMONARY Frequent infections; Respiratory distress/ insufficiency.   NEUROLOGICAL Hypotonia; Developmental delay; Gross motor delay; Loss of early motor milestones.   GASTROINTESTINAL Failure to thrive; Feeding difficulties.
PERTINENT PATIENT FINDNGS	CARDIOVASCULAR Murmur, gallop, pulsatile precordium, excessive sweating (cardiac related); Cardiomegaly; Cardiomyopathy; (hypertrophic +/- LVOTO) progressing to dilated cardiomyopathy.   PULMONARY Progressive respiratory involvement, nasal flaring; Use of accessory muscles, IC and SC retractions, decreased breath sounds in LLL; Coarse breath sounds.   NEUROLOGICAL Delayed motor milestones Hypotonia, head lag, floppy baby with ability to "slip through", frog leg position, hypertrophy of gastrocnemius muscle.   GASTROINTESTINAL Macroglossia, open mouth, low facial tone, decreased gag refles, failure to thrive, poor suck and swallow, difficulty feeding with pooling of oral secretions; hepatomegaly.
INITIAL CLINICAL FINDINGS AND INVESTIGATIONS	If GAA present, follow- up with confirmatory testing, if strong clinical suspicion.       CLINICAL STUDIES Chest X-ray- Cardiomegaly; EKG - huge R wave, short PR interval and broad QRS complex; Echocardiography - cardiomyopathy Electrophysiology (EMG/NCS) - myopathy.   LABORATORY (BLOOD OR URINE) Elevated CK, AST, ALT, LDH (in blood) Glc4 (in urine); GAA activity in dried blood spots. lymphocytes, or leukocytes with blocking antibodies to neutral mmaltase; Mutation testing in familial mutation known                                   If GAA absent, obtain confirmatory studies for definitive diagnosis.
CONFIRMATOY STUDIES	DNA GAA mutation testing   ENZYMOLOGY GAA activity testing in fibroblasts or muscle (the gold standard). Caution with muscle biopsy is needed sue to anesthesia risk.   HISTOLOGY/ HISTOCHEMISTRY Increased lysosomal glycogen Vacuolated cells
Adopted from GENETICS IN MEDICINE