DPM Podiatric Pathology 3

Question 1

Which dermatophyte species is most commonly responsible for tinea pedis (athlete's foot) in the United States?

Accepted Answer

Trichophyton rubrum

Answer

Trichophyton rubrum is the most common causative organism of tinea pedis worldwide, particularly the chronic moccasin-type presentation.

Question 2

A patient presents with a painful, pulsatile mass on the dorsum of the foot following a penetrating injury. Histology shows a false lumen lined by fibrous tissue without endothelium. What is this lesion?

Accepted Answer

Pseudoaneurysm

Answer

A pseudoaneurysm (false aneurysm) forms when blood leaks from a vessel and is contained by surrounding fibrous tissue, lacking a true endothelial lining.

Question 3

Which pathological finding best distinguishes rheumatoid arthritis from osteoarthritis in a synovial biopsy of the ankle?

Accepted Answer

Pannus formation with synovial hyperplasia and lymphocytic infiltrate

Answer

Rheumatoid arthritis features pannus—a proliferative synovial tissue with lymphocyte and plasma cell infiltration that invades and destroys cartilage.

Question 4

A diabetic patient develops rapidly spreading necrosis of the foot with crepitus on palpation. Which pathological mechanism is primarily responsible?

Accepted Answer

Gas production by anaerobic bacteria causing tissue emphysema

Answer

Necrotizing fasciitis and gas gangrene involve anaerobic bacterial species that produce gas as a metabolic byproduct, creating crepitus.

Question 5

Which histological pattern is most characteristic of a Morton's neuroma (interdigital neuroma)?

Accepted Answer

Perineural fibrosis with epineurial thickening and demyelination

Answer

Morton's neuroma is a degenerative condition showing perineural and endoneural fibrosis with demyelination, not a true neoplasm.

(DPM) Doctor of Podiatric Medicine Practice Test

(DPM) Doctor of Podiatric Medicine Practice Test

DPM Podiatric Pathology 3