Which of the following is not a feature of carcinoid syndrome: cough, wheezing, photosensitivity, flushing, diarrhea?

Photosensitivity is Not a Feature of Carcinoid Syndrome

Photosensitivity is not a feature of carcinoid syndrome. The classic features of carcinoid syndrome include flushing, diarrhea, wheezing, cough, and cardiac involvement, but photosensitivity is not among them 1.

Clinical Features of Carcinoid Syndrome

Carcinoid syndrome occurs in approximately 20% of patients with neuroendocrine tumors (NETs), particularly those originating from the midgut, and is characterized by:

1. Flushing (70% of cases)

   • Usually dry flushing without sweating
   • May be accompanied by palpitations
   • Often affects the face and upper thorax

2. Diarrhea (50% of cases)

   • Secretory in nature
   • Can be severe and debilitating

3. Wheezing/Bronchospasm

   • Due to bronchoconstrictive effects of vasoactive substances
   • Can mimic asthma symptoms

4. Cough

   • May occur during flushing episodes or independently
   • Related to bronchial involvement

5. Abdominal pain (40% of cases)

   • Often intermittent

Less common manifestations include:

• Lacrimation and rhinorrhea during flushing episodes
• Cardiac valve disease (typically in long-standing cases)
• Pellagra (in advanced cases)

Pathophysiology

Carcinoid syndrome results from the release of serotonin, tachykinins, and other vasoactive compounds directly into the systemic circulation 1. This typically occurs when:

• NETs metastasize to the liver, allowing hormones to bypass first-pass metabolism
• Primary tumors have direct venous drainage bypassing the liver
• Bronchial carcinoids release substances directly into the pulmonary circulation

Carcinoid Crisis

A severe manifestation of carcinoid syndrome is carcinoid crisis, characterized by:

• Profound flushing
• Severe bronchospasm
• Tachycardia
• Rapidly fluctuating blood pressure

This life-threatening condition is typically precipitated by anesthesia, surgery, tumor manipulation during procedures, or administration of adrenergic drugs 1.

Diagnostic Approach

Diagnosis of carcinoid syndrome involves:

• Measurement of 5-hydroxyindoleacetic acid (5-HIAA) in 24-hour urine collection
• Serum biomarkers including chromogranin A and neuron-specific enolase
• Somatostatin receptor scintigraphy for tumor localization

Why Photosensitivity is Not a Feature

While skin manifestations can occur in carcinoid syndrome, photosensitivity specifically is not a recognized feature 2. The skin manifestations that do occur include:

• Flushing (the most common cutaneous manifestation)
• Telangiectasias in some cases
• Pellagra-like features in advanced disease (due to tryptophan depletion)
• Scleroderma-like changes (in long-standing disease)

Photosensitivity is more commonly associated with other conditions such as porphyrias, medication reactions, autoimmune disorders, and certain metabolic conditions.

In conclusion, when evaluating a patient with suspected carcinoid syndrome, clinicians should look for the classic triad of flushing, diarrhea, and cardiac involvement, along with possible wheezing and cough, but photosensitivity is not part of this clinical picture.