The ACNES Diagnosis That Wasn’t: It Was Herpes Zoster

Key Takeaways

• Herpes zoster (HZ) can initially present with pain before the appearance of a rash, leading to diagnostic confusion.
• Anterior cutaneous nerve entrapment syndrome (ACNES) may be mimicked by other conditions, including HZ.
• Positive pinch test and Carnett’s sign may indicate abdominal wall neuralgia but do not exclude the possibility of HZ.

The Patient and Her History

A woman in her early 60s presented to the emergency department (ED) with sharp, left-sided abdominal pain persisting for 3 days. Yasuhiro Kano, a physician from Tokyo Metropolitan Tama Medical Centre in Tokyo, Japan, reported that the pain was relieved when she lay on her right side but worsened when lying on her left. Blood tests performed 2 days prior were normal, and oral analgesics prescribed for pain were ineffective. The patient denied other symptoms, including myalgia, fatigue, headache, chills, fever, nausea, or diarrhoea.

Findings and Diagnosis

Abdominal examination revealed tenderness in the left lower quadrant, with positive pinch and Carnett’s signs, suggesting abdominal wall neuralgia. Pain sensitivity was restricted to the left T11 dermatome, but no rash was observed. Abdominal ultrasonography findings were unremarkable.

A trigger point injection (TPI) with 1% procaine (5 mL) at the suspected site of ACNES significantly improved pain, and the patient was discharged with a diagnosis of ACNES.

Reassessment and Corrected Diagnosis

The following day, the patient returned to the ED for newly developed left lower back pain and a rash. Examination revealed erythema and small vesicles in the T12 dermatome.

Tenderness was noted upon palpation, with positive pinch and Carnett’s signs at the abdominal rash site. The tenderness and pinch sign were also positive at the rash site on the left lower back. Serum varicella-zoster virus immunoglobulin G titre increased from 15.4-fold to 102-fold, confirming a diagnosis of HZ.

Oral valaciclovir therapy was initiated, leading to symptom resolution.

Discussion

According to Kano, this case highlights the diagnostic challenges of ACNES, particularly in emergency settings. The syndrome can mimic various conditions such as acute appendicitis or cholecystitis, complicating timely diagnosis. However, there have been no previous reports of HZ presenting as ACNES.

HZ poses a diagnostic challenge, as pain can precede the rash by 1-5 days, sometimes even weeks. In rare cases, patients may not develop a rash (zoster sine herpete). Furthermore, a TPI of a local anaesthetic can alleviate pain in both zoster-associated neuralgia and ACNES, potentially leading to diagnostic uncertainty.

Management and Treatment Considerations

According to a recent review, treatment for ACNES depends on and may include reassurance, activity modification, and pain relief with topical analgesics, neuromodulators, or TPI. Patients should be reassured that, while symptoms can be distressing, they typically do not cause long-term health complications. Strenuous activities involving the core abdominal muscles should be avoided.

For mild symptoms, lidocaine patches may be sufficient, according to the authors. Some patients benefit from heating pads, while others prefer ice packs. In moderate to severe symptoms, TPI with an anaesthetic and glucocorticoid is often the most effective option. In refractory pain, chemical neurolysis or surgical neurectomy may be considered as treatment options.

This article was translated from Univadis Germany using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.