Small bowel pseudomelanosis

Small bowel pseudomelanosis
Diagnosis in short
Synonyms	pseudomelanosis duodeni (for duodenum)
LM	dark pigment in the lamina propria macrophages
Stains	iron stain +ve
Site	small bowel, stomach
Associated Dx	iron deficiency anemia, end-stage renal disease, hypertension
Clinical history	iron supplementation
Prevalence	rare
Endoscopy	+/-dark spots
Prognosis	benign

Small bowel pseudomelanosis is benign change of the small bowel that mimics melanin deposition.

In the duodenum it is known as pseudomelanosis duodeni.

Pseudomelanosis is described in the stomach, duodenum and jejunum.

General

• Rare and benign.
• Consists of iron and lipofuscin.

Associations:

• Hypertension ~90% of cases.
• Iron supplementation ~75% of cases.
• End-stage renal disease ~60% of cases.

Note:

• The associations are different than for melanosis coli.

Gross/endoscopic

• Dark spots ~35% of cases.

Microscopic

Features:

• Dark pigment in the lamina propria macrophages.

Images:

• Pseudomelanosis duodeni - several images (upmc.edu).

Stains

• Prussian blue +ve ~80% of cases.

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Small bowel

A. Stomach, Partial Excision as Part of a Sleeve Gastrectomy:
- Stomach wall within normal limits.

B. Small Bowel Wall, Partial Excision as Part of a Sleeve Gastrectomy: 
- Small bowel wall with iron containing macrophages in the mucosa,
  known as "pseudomelanosis", see comment.
- NEGATIVE for active inflammation.
- NEGATIVE for dysplasia and NEGATIVE for malignancy.

Comment:
Pseudomelanosis may be seen in the context of iron supplementation, hypertension 
and chronic renal failure. 

The macrophages are positive with an iron stain. 

See also

• Pseudomelanosis coli.