Figure 1 Petechial Rash on the Lower Extremities of an 11-year-old Boy

Image credit: Author provided

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This case was provided by Drashti Patel, BS, BA, and Jyoti Budania, MD.

The case:

In November 2023, an otherwise healthy 11-year-old boy presented to the clinic with the chief complaint of testicular discomfort. He reported mild testicular pain that worsened with physical activity, and he denied the presence of dysuria, urinary urgency, or frequency. He was recently evaluated by ENT for an episode of epistaxis, which was benign and resolved without requiring cauterization. His medical history was otherwise unremarkable, notable only for molluscum contagiosum at5 years of age and a few episodes of streptococcal pharyngitis and otitis media.

His vital signs in clinic were within normal limits, and the only additional finding at this time was a nontender, nonpruritic, and nonpalpable petechial rash on the bilateral lower extremities. His mother observed that the rash appeared to fluctuate with his activity level, worsening during periods of increased stress or activity.

Given the presence of petechiae, an initial workup was initiated, including a complete blood count (CBC), comprehensive metabolic panel (CMP), prothrombin time (PT), and partial thromboplastin time (PTT). A point-of-care urinalysis performed in the clinic revealed traces of blood in the urine. The patient appeared well and did not show any other signs of illness. He was diagnosed with viral epididymitis while pending laboratory results. He was advised to remain hydrated and to return for follow-up if his symptoms persisted or worsened. His mother agreed with this plan and committed to closely monitoring his rash.

Figure 2 & 3

Progression of the Prominent Petechial Rash Over 2 Weeks on the Lower Extremities of an 11-year-old Boy

Over the following week, he returned to our clinic. His rash had progressed, spreading to his thighs, buttocks, and the distal shaft of his penis. All of his previous labs were within normal limits, and additional workup was initiated, including a platelet function assay and measurements of serum IgA, C3, and C4 levels, along with a repeat urinalysis.

Below, take your best guess at diagnosing this patient.

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