What serum level should be assessed in a diabetic patient with a necrolytic erythematous rash?

Assessment of Glucagon Levels in Diabetic Patients with Necrolytic Erythematous Rash

The development of necrolytic erythematous rash in a diabetic patient requires assessment of serum glucagon levels. 1

Rationale for Glucagon Testing

Necrolytic erythematous rash, also known as necrolytic migratory erythema (NME), is a hallmark cutaneous manifestation of glucagonoma syndrome. This syndrome is characterized by:

• Necrolytic migratory erythema
• Elevated serum glucagon levels
• Diabetes mellitus or glucose intolerance
• Weight loss
• Anemia

Pathophysiology

The necrolytic erythematous rash occurs due to:

• Hyperglucagonemia from a pancreatic alpha-cell tumor (glucagonoma)
• Resulting hypoaminoacidemia
• Subsequent skin manifestations that can cause significant morbidity 2, 3

Diagnostic Approach

When a diabetic patient presents with a necrolytic erythematous rash, the following tests should be ordered:

1. Serum glucagon level - The primary diagnostic test 1
2. Blood glucose test - To assess diabetes control
3. Multiphase contrast-enhanced CT or MRI - To locate potential pancreatic tumor

Clinical Presentation

The rash typically presents as:

• Erythematous patches with central blistering
• Crusting and superficial necrosis
• Migratory pattern, often affecting the face, perineum, lower extremities
• Glossitis and angular cheilitis may be present

Management Implications

Early identification of elevated glucagon levels is crucial because:

• Glucagonomas are often slow-growing and potentially curable with early surgical intervention 2
• Medical management with somatostatin analogs can rapidly improve skin manifestations 4
• Amino acid supplementation may help resolve the skin rash in cases where surgery is not immediately possible 5, 6

Differential Diagnosis

Other conditions that may present with similar rashes in diabetic patients include:

• Zinc deficiency
• Pellagra
• Other nutritional deficiencies
• Pemphigus
• Drug eruptions

However, the presence of necrolytic migratory erythema specifically points toward glucagonoma syndrome, making serum glucagon measurement essential.

Common Pitfalls

1. Misdiagnosing the rash as a simple diabetic dermopathy or fungal infection
2. Focusing only on glucose control without investigating the underlying cause
3. Delaying diagnosis, which can lead to metastatic disease
4. Failing to recognize the association between the characteristic rash and glucagonoma syndrome

Early recognition of this characteristic rash and prompt measurement of serum glucagon levels can lead to timely diagnosis and potentially curative treatment of the underlying pancreatic neuroendocrine tumor.