Pictorial case study

Contributed by Dr Jean Watkins, a sessional GP in Hampshire

The two erythematous nodules become ulcerated

The case
This man had first noticed swelling on the back of his hand about nine months earlier. His GP had made a diagnosis of arthritis and prescribed an NSAID to ease the symptoms.

Six months later he was alarmed by the development of two erythematous/bluish nodules in the area of the swelling, which subsequently broke down and ulcerated.

The GP then prescribed a course of flucloxacillin, assuming a bacterial infection. When there was no response and lesions seemed to be spreading up his arm along the line of the lymphatic drainage, together with enlarged lymph glands in the axilla, the patient was referred to the dermatologist.

What is the diagnosis, management and differential diagnoses?

A swab was taken from the lesion but, in view of the history, appearance of the lesion and the fact that the patient kept tropical fish, a clinical diagnosis of fish tank granuloma was made.

As in this case, it is common for fish tank granuloma to be initially misdiagnosed and treatment delayed. The diagnosis may be confirmed by a swab for culture and sensitivities. If this is inconclusive, the lesion may be biopsied.

The organism is usually sensitive to rifampicin, tetracycline, co-trimoxazole or clarithromycin. Resolution may take several months and the drug should be continued for four to six weeks after clearance of the lesions. Surgical drainage or debridement is not usually necessary unless the patient experiences persistent pain.


  • Rheumatoid arthritis
  • Squamous cell carcinoma
  • Leishmaniasis
  • Sarcoidosis

Cutaneous leishmaniasis

  • Caused by parasites of the genus Leishmania and transmitted by sandfly bites.
  • Small papules gradually enlarge to form dark red, firm, indurated nodules.
  • Crust forms on surface, which then ulcerates.
  • Usually on exposed areas such as the face.
  • Usually a clinical diagnosis but may be confirmed if parasite found in biopsy.

Have you registered with us yet?

Register now to enjoy more articles and free email bulletins


Already registered?

Sign in

Just published

Dr Zoe Norris

GPDF slashes costs and overhauls funding rules to 'restore trust' with GPs

The General Practice Defence Fund (GPDF) has cancelled contracts worth hundreds of...

Churchill Gardens

Scheme from Brazil helps address health inequalities in London practice

A scheme involving community health and wellbeing workers, which is based on a long-standing...

Talking General Practice logo

Podcast: How an initiative from Brazil could help general practice and improve outcomes

Dr Matt Harris and London GP Dr Connie Junghans Minton explain how an initiative...

Medical centre sign

One in three GP practices in Northern Ireland faced serious closure risk in past 18 months

One in three GP practices in Northern Ireland have faced a serious risk of closure...

BMA sign

BMA warns Treasury 'many practices' will close without emergency financial support

GP leaders have urged the Treasury to agree emergency funding to support general...


Practices can use £172m PCN cash to support staff pay rises, GP leaders say

Practices can use their share of Β£172m from the 2023/24 investment and impact fund...