History and exam

Key diagnostic factors

common

presence of risk factors

Strong risk factors include a family history of anaemia, jaundice, splenectomy, or known HS; also Northern European ancestry.

pallor

Non-specific sign (with or without symptoms). May indicate presence of anaemia.

Provokes blood count and blood smear examination, which may reveal the diagnosis.

Anaemia is not necessary for the diagnosis.

Acute onset of pallor, lethargy, and fever may occur after parvovirus B19 infection.

jaundice

Due to elevated levels of unconjugated bilirubin. May or may not be present. It is likely to be present in severe HS, and will vary with time.

Non-specific sign, but should trigger a full blood count and blood smear review. It may be exacerbated by complicating conditions, such as Gilbert's syndrome.[24][Figure caption and citation for the preceding image starts]: Jaundiced sclera in eye of child with HSFrom the collection of Paula Bolton-Maggs, University of Manchester, UK; used with permission [Citation ends].com.bmj.content.model.Caption@44f9dd9b

splenomegaly

The spleen is nearly always palpable in HS. It may be moderately enlarged, but rarely huge.

Splenomegaly may be the only clinical feature in the presence of a normal haemoglobin and absent hyperbilirubinaemia, but the blood smear will usually be diagnostic.

The splenomegaly generally does not cause any symptoms or clinical consequences. However, during hyperhaemolytic crises, the spleen rarely may become acutely and significantly enlarged and cause left upper quadrant abdominal pain and symptoms of early satiety. The spleen generally shrinks to its previous size between episodes.

Other diagnostic factors

common

fatigue

May indicate presence of anaemia.

However, anaemia is not necessary for the diagnosis.

Acute onset of pallor, lethargy, and fever may occur after parvovirus B19 infection.

uncommon

hydrops foetalis or stillbirth

Very rare presentation of HS, due to severe anaemia (e.g., when infant inherits defects in membrane proteins from both parents).[9][10][11]

Risk factors

strong

family history of splenectomy, anaemia, jaundice, or HS

Approximately 75% of cases of HS are dominantly inherited. Therefore, there may be a history of anaemia, jaundice, HS, or splenectomy in a parent (who may not know the reason for the surgery).[5]

Non-dominant HS can occur as a result of inheritance of a pathogenetic mutation from one parent and a silent low-expressed allele from the other, or from de novo mutations.

at risk demographic

HS is found in all populations but is most common in people of Northern European ancestry. The prevalence in this group is approximately 1 in 5000.[5][12]

HS is rare in black people.

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