Medical Mnemonics

Henoch-Schönlein Purpura Mnemonic – “PAAR the IgA”

June 1, 2025

Every now and then in paediatrics (or when you’re the unlucky on-call medic asked to review the child in the ER), you’ll meet a kid who looks like they lost a fight with a purple marker — palpable purpura on the legs, crying from abdominal pain, and passing Coca-Cola-colored urine.

If that rings a bell louder than your ward call buzzer, congratulations — you’ve just met Henoch-Schönlein Purpura (HSP). 🎯

Table of Contents

💡 What is HSP, Really?

Henoch-Schönlein Purpura, now more formally called IgA Vasculitis, is the most common small-vessel vasculitis in children. It’s an IgA immune complex–mediated condition that loves to mess with skin, joints, GI tract, and kidneys — because why stop at one system when you can hit four?

I still remember a 6-year-old boy at SKBZ Hospital, Quetta who came in with colicky abdominal pain and what his mother called “mosquito bites” on the legs — except those bites didn’t blanch, didn’t itch, and were multiplying like residents during a grand round. Turns out, the bugs were innocent. The kidneys, not so much.

HSP Mnemonic – “PAAR the IgA”

Letter	System Involved	Clinical Feature
P	Purpura (skin)	Palpable purpura, typically on buttocks & lower limbs
A	Arthralgia/Arthritis (joints)	Often knees & ankles; transient and non-deforming
A	Abdominal pain (GI)	Colicky pain, GI bleeding, intussusception risk
R	Renal involvement	Hematuria, proteinuria; can progress to nephritis

🔍 Bonus: Always remember IgA deposition in vessel walls on biopsy – always asked in the exam!

🔬 Diagnostic Pearls

Palpable purpura is a must-have. If there’s no rash, rethink the dx.
Labs: ↑ serum IgA, hematuria ± proteinuria on urine dipstick
Skin or renal biopsy (if needed): IgA deposition in small vessels

In Quetta, we once had a case misdiagnosed as ITP (because “rash and low platelets” was the first reflex). But turns out — platelets were normal, urine was dirty, and voila — classic HSP.