Acute onset lower extremity pain and inability to ambulate in an immunocompromised teenager: a case report

Structured Abstract Background Herpes zoster is an uncommon clinical entity in the pediatric population, with incidence increasing with age. The syndrome is characterized by neuralgia and vesicular rash due to reactivation of latent varicella zoster virus within the dorsal root ganglion. Case presentation A 15-year-old immunocompromised male with history including orthotopic heart transplant and developmental disability presented with subacute right lower extremity pain and refusal to ambulate. The patient had initially been diagnosed and treated for muscle strain and urinary tract infection during a recent emergency department visit. Differential diagnoses included osteomyelitis, myositis, occult fracture, venous thrombus, or intra-abdominal pathology. Laboratory workup revealed elevated inflammatory markers (ESR 16, CRP 1.4). Femur/pelvis magnetic resonance imaging identified proximal right rectus femoris edema. CT abdomen/pelvis incidentally noted disc bulge and retrolisthesis of L5 on S1. Physiatry was consulted for suspected lumbar radiculopathy/radiculitis. He denied low back pain or radiation. Examination revealed an uncomfortable but nontoxic patient. Right lower extremity skin inspection identified a vesiculopapular rash in the L4 dermatomal distribution. Lower extremity strength and sensation was intact, with notable right medial thigh allodynia, guarding and pain-limited right lower-extremity active range of motion. Straight-leg raise testing was negative. Physiatry recommended shingles workup in the setting of immunosuppression. Varicella zoster virus polymerase chain reaction of vesicular fluid returned positive. Conclusions This patient’s chronic anti-graft rejection immunosuppression and recent urinary tract infection had likely elicited viral reactivation and the clinical manifestation of herpes zoster. The patient’s neuralgia and viral exanthema within the distribution of the affected dermatome resolved gradually after standard treatment with intravenous acyclovir and initiation of gabapentin. This case emphasizes the importance of a broad differential diagnosis in pediatric patients presenting with acute pain, including consideration of herpes zoster, and underscores the importance of thorough physical examination with careful skin inspection, including full exposure of the affected extremity to avoid diagnostic anchoring.