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NIDDM Presenting as Pseudo-Allergy

By Allen E Gale, Consultant Physician (Allergy)

A diagnosis of diabetes was suspected in 47 cases referred for evaluation of allergy as a cause of a variety of complaints. Method. The diagnosis of Type 2 Non Insulin Dependent Diabetes Mellitus (NIDDM) was confirmed by an Oral Glucose Tolerance Test (OGTT). Concurrent insulin levels revealed a trend to lower values as diabetes worsened: 22 of these cases had normal fasting blood glucose. An hypothesis is proposed to explain the link between NIDDM and pseudo-allergy.

The diagnosis of NIDDM was suspected in each case on the basis of clinical features revealed in the history of patients presenting with a diversity of complaints. Other investigations had failed to discover the cause and the referring doctor had asked whether allergy was the culprit. The clinical features that had prompted referral are listed in Table 1. A two hour OGTT after a loading dose of 75 grams of glucose was performed on each patient with collection of serum for insulin assays on the fasting, one and two hour specimens.


The 47 patients with NIDDM fall into three groups.


  1. Most Severe:- Fasting glucose* >or= 7; 2 hour glucose >or= 11.1
  2. Less severe:-Fasting glucose >or= 6.1 but < 7; 2 hour glucose >or= 11.1
  3. Fasting glucose < 6.1; 2 hour glucose >or= 1.1

*Glucose (mmol/L) levels after 75 grams of glucose in the OGTT. The fasting levels of 7mmol/L [126mg/L] & 6.1mmol/L [110mg/L] were chosen to separate the three groups (Alberti et al 1998).

A. Fasting glucose between 7.0 and 11.6 & 2 hour glucose between 11.2 and 22.7. .. 10 cases.

B. Fasting glucose between 6.2 and 6.7 & 2 hour glucose between 11.6 and 14.9 15 cases.

C. Fasting glucose between 2.4 and 6 7 & 2 hour glucose between 11.2 and 17.1 22 cases.

The insulin (microU/ml) levels during the OGTT of these 47 patients were:

(A) Fasting insulin 7-42; at one hour 3-111; at two hours 28-88 microU/ml

(B) Fasting insulin 8-42; at one hour 33-219; at two hours 31-175 microU/ml

(C) fasting insulin 2-45; at one hour 28-634; at two hours 40-1124 microU/ml


Bearing in mind that insulin resistance associated with hyperinsulinemia is

the patho-physiological basis of diabetes (Foster ) it would appear

reasonable to propose the following hypothesis as the underlying

mechanism whereby the metabolic changes associated with the early

development of NIDDM present in such a bizarre variety of ways.

Hypothesis:- "The metabolic changes due to hyperinsulinemia and insulin

resistance may adversely affect every organ system in the body; the system

involved depending on whether insulin resistance is pre-receptor, receptor

or post-receptor; the particular symptom complex depending on which

mechanism or mutation causes the insulin resistance."

The exact mechanism whereby these clinical features are related to NIDDM

is unclear. Some authors have suggested that the acronyms NIDDM and

IDDM should refer to "Non Immune Dependent Diabetes Mellitus" and

"Immune Dependent Diabetes Mellitus" respectively. This however does not

exclude immunological factors from NIDDM as many of the latter progress

to IDDM. On suggesting the performance of an OGTT to these patients,

many responded by stating that "it couldn't be diabetes as a recent blood

sugar was normal". This reflects the practice of many clinicians who rely on

the evaluation of fasting blood glucose as a routine screening test for

diabetes. Whilst this opinion is supported by the American Diabetes

Association (ADA), the World Health Organisation (WHO) differs in

recommendations on use of the OGTT arguing strongly for the retention of

the OGTT (Colman et al 1999).

Quite clearly this series of cases supports the concerns that many cases of

diabetes will be missed if the OGTT is replaced by reliance on a fasting

blood sugar level. Furthermore this series illustrates the worsening of

glucose values in the face of declining insulin levels (Foster 1999).


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