Differential diagnosis

Differential Diagnosis
Dr. M. Nasar Sayeed Khan
Associate Professor of Psychiatry
SIMS and SHL
nasarsayeed@yahoo.com

The Diagnostic Problem
• DSM Diagnosis = a somewhat paradigmatic
symptoms cluster at the syndromal level of
abstraction
• However, individuals usually present clinicians
with a single symptom/small set of symptoms:
– That they find most distressing
– That they are most comfortable discussing
• Getting from a single or small number of related
symptom to a diagnosis useful for treatment is
what differential diagnosis is all about.

Step #1
• Is the presenting symptom for real?
– This does not imply that one should always
mistrust what the patient says.
– However there are diagnoses in which
conscious feigning of symptoms is usual
(Malingering and Fictitious Disorder) and one
in which unconscious feigning of symptoms is
usual (Conversion Disorder).

Step #1 (corollaries)
1. Is this a situation in which feigning of symptoms is
more typical: ER, forensic evaluation, prison, inpatient
unit?
2. Does the presentation of symptoms conform more to a
popular view of a disorder than to an actual clinical
entity?
3. Do the symptoms shift significantly from one clinical
encounter to the next?
4. Do the symptoms mimic the presentation of a role
model like a parent or another patient?
5. Is the patient unusually manipulative or suggestible?

Step #2
• Rule out substance etiology (drugs of
abuse, medications, toxin exposure).
1. Does the individual use any substances?
• This includes dependence, abuse, recreational
use, medical use, and environmental exposure.
• This will involve a thorough history and
evaluation, laboratory tests, and toxicology.
• In an aging population with less cautious use of
parmacotherapy, medication use is an increasing
concern.

Step #2
2. What is the etiologic relationship between
substance use and psychiatric symptoms?
a) The symptoms are a direct result of the effects of
the substance use.
b) The substance use is secondary to the
psychiatric symptoms.
c) The psychiatric symptoms and substance use
are independent of each other.

Step #2
– Temporal sequence is a helpful, but not infallible,
guide.
• If the onset of psychiatric symptoms clearly precedes the
onset of substance use, it is probably a primary psychiatric
disorder.
• If the onset of substance use clearly precedes the psychiatric
symptoms than the symptoms are more likely to be
substance induced.
• If the psychiatric symptoms abate in about 4 weeks after
substance intoxication or withdrawal, the symptoms are more
clearly substance induced.
– Excepting Substance Induced Persisting Dementia or
Amnesiac Disorder.

Step #2
– Caveats
• Often individuals suffering from substance use and
psychiatric symptoms are not the best historians of
their own experience.
• Substance misuse and psychiatric disorders often
have their onset in late adolescence without any
causative link.
• If psychiatric symptoms are severe and pose a risk
to self or others, waiting 4 weeks to determine
etiology raises serious questions.

Step #2
3. Is the pattern of substance use or withdrawal sufficient to
account for the symptoms?
• Is the nature, amount, and duration of substance use consistent
with the observed symptoms?
• Not all substances nor all dose levels of specific substances
produce specific symptoms.
4. Is the pattern of substance use consistent with an attempt to
relieve the symptoms?
5. Are there other factors like heavy genetic loading for a specific
psychiatric problem that point to a non-substance induced
etiology?
6. In the absence of persuasive evidence in either direction,
could the two disorders simply be co-morbid?
back

Step #3
• Rule out a disorder due to a general medical
condition?
– The clinical implication of this step are profound.
– Differential diagnosis is complicated:
• Symptoms of some psychiatric conditions and many general
medical conditions can be identical.
• Sometimes the first presenting symptom of a general medical
condition is psychiatric.
• The relationship between medical conditions and psychiatric
conditions can be complicated
• Patients are often seen in mental health setting where there
is low expectation of and little familiarity with general medical
conditions.

Step #3
– Just as with substance use, virtually any psychiatric
presentation can be caused by the direct physiologic
effects of a general medical condition (e.g. Mood
Disorder due to Hypothyroidism).
• A good diagnostic evaluation should contain a thorough
history and physical as well as tests for those medical
conditions most likely to cause the presenting symptoms (
thyroid function tests for depression, brain imaging for late-
onset psychosis)
• In social work practice, involvement of a physician with good
diagnostic skills, like and Internist, in the evaluation process
is very important.

Step #3
– If a general medical condition is present, its etiologic
relationship, if any, to the psychiatric symptoms
must be established.
1. The medical condition causes the psychiatric symptom by
direct action on the CNS.
2. The general medical condition causes the psychiatric
symptoms through a indirect or psychological mechanism.
3. Medication taken for the medical condition causes the
psychiatric symptoms.
4. The psychiatric symptoms adversely effect the medical
condition.
5. The psychiatric symptoms and the medical condition are
purely coincidental,

Step #3
– There are some clues that are helpful, but not
infallible, in making the clinical judgment
mentioned earlier.
• Temporality: do psychiatric symptoms follow the
onset of the medical condition, vary in intensity
with it, and disappear when it is resolved?
– Remember that psychiatric symptoms can precede, by
some time, the onset of some medical problems or not
occur until late stages of others.

Step #3
• Atypicality: are the psychiatric symptoms atypical in pattern,
age of onset, or course.
– e.g. significant weight loss and severe fatigue with mildly
depressed mood, first onset of Manic Episode in an elderly
individual, severe disorientation accompanying psychotic
symptoms.
– Remember, manifestation of psychiatric disorders is very
heterogeneous and atypical presentations are not unknown.
– If you determine that a medical condition is causing
the psychiatric symptoms, determine which DSM-IV-
TR diagnosis of Mental Disorders Due to a General
Medical Condition best describes the presentation.
• A decision tree or algorithm is very helpful.

Step #4
• Determine the specific primary disorder(s).
– The arrangement of disorders in the DSM-IV-TR into
broad categories of disorders is done to somewhat
facilitate this process:
– Disorders First Diagnosed in Infancy, Childhood, or
Adolescence; Delirium, Dementia, Amnestic, and
other Cognitive Disorders; Substance-Related
Disorders; Schizophrenia and other Psychotic
Disorders; Mood Disorders; Anxiety Disorders;
Somatoform Disorders; Factitious Disorders;
Dissociative Disorders; Sexual and Gender Identity
Disorders; Eating Disorders; Sleep Disorders;
Impulse-Control Disorders; Adjustment disorders;
Personality Disorders

Step #4
• The problem is that many disorders
share common symptoms:
Insomnia
Acute Stress Disorder
Cyclothymic Disorder
Delirium
Dysthymic Disorder
GAD
Hypomanic Episode
Major Depressive Disorder
Manic Episode
Mixed Episode
Nightmare Disorder
PTSD
Schizoaffective Disorder
Schizophreniform Disorder
Schizophrenia
Substance Use/Withdrawal
Weight Loss
Anorexia Nervosa
Dysthymic Disorder
Hypomanic Episode
Manic Episode
Mixed Episode
Substance Intoxication
Irritability
Acute Stress Disorder
ASPD
Attentional Deficit/Hyperactivity Disorder
BPD
Conduct Disorder
Cyclothymic Disorder
Delusional Disorder
Dysthymic Disorder
GAD
Hypomanic Episode
Manic Episode
Mixed Episode
PTSD
Schizoaffective Disorder
Schizophreniform Disorder
Schizophrenia
Substance Use/Withdrawal

Step #4
Dysthymic Disorder
must be differentiated
from . . .
In contrast to Dysthymic Disorder, the
other condition . . .
Major Depressive Disorder is characterized by one or more major
depressive episodes; both can be diagnosed
if the MDE occurs after the first 2 yrs. of
Dysthymic Disorder
Depressive symptoms
associated with chronic
Psychotic Disorder
occurs exclusively during the psychotic
disturbance
Cyclothymic Disorder is characterized by hypomanic periods as well
as depressive periods.
Nonpathological periods of
sadness
is characterized by short duration, few
symptoms, an no significant impairment or
distress

Step #5
• If the symptom pattern or the severity of impairment or
distress does not meet criteria for a specific diagnosis,
differentiate adjustment disorder from not otherwise
specified.
– If the clinical judgment is made that the symptoms developed
from a maladaptive response to a psychosocial stressor, then
adjustment disorder appropriate.
– If the judgment is that the stressor is not responsible for the
development of the symptoms, than the relevant Not Otherwise
Specified category can be diagnosed.
– Given the ubiquity of stressors, the point is not whether a
stressor is present or not but whether it is the etiology of the
symptoms.

Step # 6
• Establish the boundary with no mental disorder
– This is an obvious but not always an easy step to
take.
– Many symptoms are so ubiquitous that they occur at
least briefly in the lives of most people.
• At some time most individuals will experience symptoms of
anxiety, depression, difficulty sleeping, or sexual dysfunction.
• It is important not to pathologize what is really the human
condition.
– The disturbance must cause “clinically significant
impairment or distress in social, occupational, or other
important areas of functioning.”

Step # 6
• The diagnosis of Hypoactive Sexual Desire
Disorder should not be made in someone with low
sexual desire, who is not in a current intimate
relationship with anyone, and who is not
particularly bothered by it.
– The problem is that what is “clinically
significant” is greatly influenced by cultural
context, the setting in which the individual is
seen, clinician bias, client bias, and
availability of resources.
– Unfortunately there is little solid research and
no hard and fast rules that can guide this
decision.

Comorbidity
• Although it is best to follow the principle of
parsimony, it is also important to remember that
most diagnoses are not mutually exclusive.
– In an individual with delusions, hallucinations, and
mood symptoms a decision must be made among
Schizophrenia, Schizoaffective Disorder, and Mood
Disorder with Psychotic Features.
– In an individual with multiple unexpected panic
attacks, significant depression, and a maladaptive
perfectionistic and rigid personality style the
diagnoses of Major Depressive Disorder, Panic
Disorder, and Obsessive-Compulsive Personality
Disorder may all apply.

Comorbidity
• Using multiple diagnoses is neither good nor
bad so long as the implications are
understood.
• Do not hold the mistaken view that multiple
descriptive diagnoses are actually
independent:
1. A may cause or predispose to B (ASPD, SUD)
2. B may cause or predispose to A (OCD, Eating Disorders)
3. An underlying condition C may predispose to both A and B
(PTSD, Agoraphobia, SUD)
4. A and B may be part of a larger syndrome artificially split in the
diagnostic system (PTSD, BPD)
5. The comorbidity is a chance co-occurrence in conditions with
high base rates (MDD and SUD)

Comorbidity
• Having more than one DSM-IV-TR
diagnosis does not mean that there is
more than one underlying
pathophysiological process.
• The diagnoses are not entities but
descriptive building blocks, useful for
communicating diagnostic information and
guiding therapeutic choices.

Practice
• Consider the case of a 38 year old married male
who is referred for evaluation after a second
DUI. He readily admits that he is a regular and
heavy drinker, that he has tried to stop drinking
several times but without any sustained success,
and that he often drinks more than he intends.
He also complains of feelings of intense
sadness, difficulty sleeping, weight loss,
constant sense of fatigue, feelings of guilt and
worthlessness, and occasional thoughts of
suicide.

Practice
• This is not an atypical presentation and poses a
serious differential challenge.
• Although this is a kind of forensic evaluation, let
us assume that there is no reason to believe that
the individual is not being perfectly honest about
his symptoms.
• Let us further assume that a recent history and
physical reveals no apparent medical problem
which might explain the symptoms.

Practice
• The diagnostic question then is: Is this an
individual whose Major Depressive
Disorder is secondary to his Alcohol
Dependence, or whose Alcohol
Dependence is secondary to his Major
Depressive Disorder, or who has both
Major Depressive Disorder and Alcohol
Dependence as comorbid conditions.
• Diagnostic tree

Practice
• Consider the case of a 28 year old, unmarried woman, who seeks help
because of panic attacks. She was perfectly fine until she was in her last
year of graduate studies in molecular biology and was attacked and
carjacked in the library parking lot late one night. Her attacker forced her to
dive, at knife point, to a deserted area where he raped, beat, and left her.
She was so shaken by the experience that she dropped out of school
without finishing her degree. She still has nightmares about the attack and
takes benzodiazepines, off and on, to help her sleep. She eventually got a
job as a technician in a medical lab and was doing better until the lab
started running a late shift. When she works late, the thought of having to
go to her car in a dark and deserted parking lot makes her feel like she is
smothering. When she can convince someone to go with her to her car, she
feels better. But several times she could not find anyone and her heart beat
so fast and hard she was convinced she was about to die. She doesn’t want
to loose her job but she also doesn’t want to continue to live as she has for
the past several months.

Practice
• The presenting symptom is panic attacks.
The Diagnostic question is whether this
symptom is the result of the after effects of
benzodiazepine use, a developing anxiety
disorder, or trauma.
• Diagnostic tree

Practice
• Consider the case of a 57 year old, widowed, female who is brought to the
emergency room by EMTs. She was wandering around her neighborhood in a
flowered house dress and slippers early on a chilly November morning. The
neighbors saw her and attempted to talk to her but when she didn’t seem to make a
lot of sense, they called 911. The paramedic says that in talking to the neighbors he
discovered that she has lived in her house for at least 20 years. Five years ago her
husband died and since then they have seen little of her. They said that she has no
visitors except the local grocery that delivers and the local liquor store which also
delivers. The paramedic says that when asked if she knew were she was she
responded, “Yes, in San Francisco on my honeymoon, but I seem to have gotten lost
and can’t remember how to get back to the hotel. I’ll be fine as soon as I can find my
husband.”
• She is very thin and looks considerably older than her age. Her skin has a somewhat
sallow and yellowish pallor that seems to be more pronounced in her neck and upper
chest. There is a very faint smell of wine about her but she does not appear to be
intoxicated. Her BP is in normal range for her gender and age but here temperature is
slightly elevated (99.8 F). When questioned about what has happened she is either
non responsive or talks about recently being married and about the plans she and her
husband have once they return to Lexington. She appears to be more confused than
frightened. When asked were she thinks she is now, she responds, “In the Visitor’s
Aid Center where we’ll get everything sorted out shortly.”

Practice
• Contact with the local grocery reveals that she generally orders the
same things every week: bread, eggs, meat, assorted vegetables,
milk, orange juice, occasionally oil or flower, and always a large
bottle (100 tabs) of extra strength acetaminophen. Contact with the
liquor store reveals that she always orders 3 bottles of white wine,
usually pinot grigio.
• This case presents very considerable diagnostic challenges, some
of which may be beyond your current expertise. It is included for the
following reasons:
– Because there will be cases beyond your expertise no matter how much
you know;
– It illustrates the need to be tentative in diagnosis, especially when there
is much that is unclear;
– It is a case in which treatment based on the wrong diagnosis can be
fatal.
• Diagnostic Tree

Differential diagnosis

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