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Protein C deficiency severity – protein C levels and severity of protein C deficiency

Severity Classification

Protein C deficiency severity is determined by the remaining
Protein C activity level

Mean protein C (PC) levels in healthy individuals1

Schema Severity Classification 04

The severity of PC deficiency is determined by the remaining PC activity level. In healthy individuals, PC levels, or mean plasma concentrations of PC, increase with age since PC matures later compared to other coagulation proteins, as can be observed above. PC concentration remains relatively low throughout childhood until after puberty, when it reaches activity levels of 65–135 IU/dL, which is considered to be normal for an adult.1



According to Goldenberg et al., adults with PC activity levels between 21 and 64 IU/dL are regarded as having mild PC deficiency, while moderately severe PC deficiency occurs when activity is between 1 and 20 IU/dL.1

Severe deficiency is defined by PC activity lower than 1 IU/dL.1 People with congenital PC deficiency caused by homozygous or compound heterozygous mutations have severe deficiency (SCPCD), whereas those with heterozygous mutations tend to have mild/moderate PC deficiency,1,2 with plasma PC activity being about half of the normal level of activity.3


Protein C Activity Level (IU/dL)1,*
No deficiency
Moderately severe
< 1

*Adult levels


  1. Goldenberg N, Manco-Johnson M. Protein C deficiency. Haemophilia. 2008;14(6):1214–1221.

  2. Chalmers E, et al. Purpura fulminans: recognition, diagnosis and management. Archives of Disease in Childhood. 2011;96(11):1066-1071.

  3. Marlar RA, et al. Report on the diagnosis and treatment of homozygous protein C deficiency. Report of the Working Party on Homozygous Protein C Deficiency of the ICTH-Subcommittee on Protein C and Protein S. Thromb Haemost. 1989;61(3):529-31.

SCPCD - Key Management info  

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