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PubMed This is a summary of 20 peer-reviewed journal articles Updated
Endocrinology

The Types of CAH: Classic vs. Non-Classic

At a Glance

Congenital Adrenal Hyperplasia (CAH) has three main types depending on enzyme activity: severe Classic Salt-Wasting, Classic Simple Virilizing, and milder Non-Classic CAH. Your specific CYP21A2 gene mutations determine your type, which guides your symptoms and treatment plan.

Congenital Adrenal Hyperplasia (CAH) is not a single experience; it is a spectrum. The “type” of CAH a person has depends entirely on how much of the 21-hydroxylase enzyme their body can produce [1][2]. This is determined by the specific instructions in your DNA, known as the CYP21A2 gene [3].

Medical teams generally divide CAH into three main categories. Understanding where you or your child falls on this spectrum helps clarify what medications are needed and what to expect in the future.

The Three Major Types of CAH

Type Enzyme Activity Key Hormonal Deficiencies Timing of Diagnosis
Classic: Salt-Wasting 0% to <1% Lacks Cortisol & Aldosterone Newborn (via screening or crisis)
Classic: Simple Virilizing ~1% to 2% Lacks Cortisol; makes enough Aldosterone Newborn or early childhood
Non-Classic (Late-Onset) 20% to 50% Makes enough of both for daily needs Childhood, adolescence, or adulthood

1. Classic Salt-Wasting (The Most Severe Form)

This is the most common form of Classic CAH, occurring in about 75% of cases [1]. Because the enzyme activity is nearly zero, the body cannot make cortisol (the stress hormone) or aldosterone (the salt-retaining hormone) [4][5]. Without aldosterone, the body cannot hold onto salt, which is filtered out through the urine. This can lead to a “salt-wasting crisis”—a medical emergency involving dehydration and low blood pressure—if not treated promptly [5][1].

2. Classic Simple Virilizing

In this form, the body has just enough enzyme activity (usually around 1-2%) to make the aldosterone needed to balance salt, but it still cannot make enough cortisol [6][7].

(Note: The line between Salt-Wasting and Simple Virilizing can sometimes be fluid. Some Simple Virilizing patients may eventually require fludrocortisone if their renin levels become elevated, indicating their body is struggling to hold onto salt [7].)

The main challenge here is virilization. Virilization refers to the development of male-typical physical characteristics caused by an excess of androgens (male-type hormones) [8]. In newborn girls, this may result in ambiguous genitalia [9]. In both boys and girls, it can lead to rapid growth, early pubic hair, and advanced “bone age” (where bones mature too quickly, potentially leading to shorter adult height) [10].

3. Non-Classic CAH (The Milder Form)

Non-classic CAH (NCCAH) is much more common and may not be detected until later in life [11]. People with NCCAH produce enough cortisol and aldosterone for their basic daily needs. However, the system is still slightly “leaky,” causing a mild backup that leads to extra androgens [12][13].

In women, NCCAH can look very similar to Polycystic Ovary Syndrome (PCOS), causing symptoms like irregular periods, severe acne, or excess body hair (hirsutism) [11][14]. Many men with NCCAH have no symptoms at all and may only discover they have it through genetic testing [11].

How Your Genes Decide

Your “genotype” is the specific pair of mutations you inherited—one from each parent. Doctors classify these mutations into groups based on how much “work” the resulting enzyme can do:

  • Null / Group A Mutations: These are “broken” instructions that result in 0% enzyme activity, leading to the Salt-Wasting form [15][6].
  • Group B Mutations: These provide a tiny bit of activity (~1-2%), typically leading to the Simple Virilizing form [16][6].
  • Group C Mutations: These are “mild” instructions (like the common V281L mutation) that allow for 20-50% activity, leading to Non-Classic CAH [17][7].

Because you have two copies of the gene, your “type” is usually determined by the mildest mutation you have. For example, if you inherit a “Null” mutation from your father but a “Group C” mutation from your mother, you will likely have Non-Classic CAH [18][15]. Identifying these specific mutations through CYP21A2 molecular genetic analysis is the gold standard for confirming your type and planning your care [19][20].

Common questions in this guide

What is the difference between Classic and Non-Classic CAH?
Classic CAH is typically diagnosed in infancy and involves severe deficiencies of cortisol, and sometimes aldosterone. Non-Classic CAH is a milder form that is often diagnosed later in childhood or adulthood, primarily causing symptoms related to excess male-type hormones, such as severe acne or irregular periods.
What does salt-wasting mean in CAH?
Salt-wasting is a medical emergency that happens in the most severe form of CAH when the body cannot produce a hormone called aldosterone. Without aldosterone, the body is unable to hold onto sodium, leading to severe dehydration and low blood pressure.
What is Simple Virilizing CAH?
Simple Virilizing CAH is a classic form of the condition where the body can make enough aldosterone to balance salt, but cannot produce enough cortisol. This deficiency leads to an overproduction of androgens (male-type hormones), which can cause ambiguous genitalia in newborns, rapid growth, and early puberty.
How do my genetics determine my CAH type?
CAH is caused by mutations in the CYP21A2 gene. You inherit one copy of this gene from each parent. Because you have two copies, your specific CAH type is usually determined by the mildest genetic mutation you inherited.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Which group of genetic mutations was identified in my/my child's CYP21A2 gene (Null, Group A, B, or C)?
  2. 2.Does this specific genotype predict a high risk for salt-wasting crises?
  3. 3.For females: What is the Prader score, and how does it affect our long-term care plan?
  4. 4.If this is Non-Classic CAH, do I need to take glucocorticoids now, or only if I'm trying to conceive?
  5. 5.How often should we monitor electrolyte levels to ensure aldosterone needs are being met?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (20)
  1. 1

    Genetic characterization of a large cohort of Argentine 21-hydroxylase Deficiency.

    Fernández CS, Taboas M, Bruque CD, et al.

    Clinical endocrinology 2020; (93(1)):19-27 doi:10.1111/cen.14190.

    PMID: 32289882
  2. 2

    Evaluation of a Two-Tier Screening Pathway for Congenital Adrenal Hyperplasia in the New South Wales Newborn Screening Programme.

    Lai F, Srinivasan S, Wiley V

    International journal of neonatal screening 2020; (6(3)):63 doi:10.3390/ijns6030063.

    PMID: 33117905
  3. 3

    The spectrum of CYP21A2 gene mutations in patients with classic salt wasting form of 2l-hydroxylase deficiency in a Chinese cohort.

    Liu Y, Zheng J, Liu N, et al.

    Molecular genetics & genomic medicine 2020; (8(11)):e1501 doi:10.1002/mgg3.1501.

    PMID: 32959514
  4. 4

    Steroid 21-hydroxylase deficiency in congenital adrenal hyperplasia.

    Parsa AA, New MI

    The Journal of steroid biochemistry and molecular biology 2017; (165(Pt A)):2-11 doi:10.1016/j.jsbmb.2016.06.015.

    PMID: 27380651
  5. 5

    Congenital adrenal hyperplasia with salt-wasting crisis and arrhythmia: a case study.

    Canlas JF, Ponmani C

    BMJ case reports 2019; (12(1)) doi:10.1136/bcr-2018-227565.

    PMID: 30700462
  6. 6

    Linking the degree of virilization in females with congenital adrenal hyperplasia to genotype.

    Gurgov S, Bernabé KJ, Stites J, et al.

    Annals of the New York Academy of Sciences 2017; (1402(1)):56-63 doi:10.1111/nyas.13370.

    PMID: 28640966
  7. 7

    Genetic Characterization of a Cohort of Italian Patients with Congenital Adrenal Hyperplasia Due to 21-Hydroxylase Deficiency.

    Concolino P, Perrucci A, Carrozza C, Urbani A

    Molecular diagnosis & therapy 2023; (27(5)):621-630 doi:10.1007/s40291-023-00666-x.

    PMID: 37548905
  8. 8

    Antenatal Diagnosis and Treatment in Congenital Adrenal Hyperplasia Due to 21-hydroxylase Deficiency and Congenital Adrenal Hyperplasia Screening in Newborns

    Yavaş Abalı Z, Kurnaz E, Güran T

    Journal of clinical research in pediatric endocrinology 2025; (17(Suppl 1)):33-43 doi:10.4274/jcrpe.galenos.2024.2024-6-10-S.

    PMID: 39713885
  9. 9

    Alternative pathway androgen biosynthesis and human fetal female virilization.

    Reisch N, Taylor AE, Nogueira EF, et al.

    Proceedings of the National Academy of Sciences of the United States of America 2019; (116(44)):22294-22299 doi:10.1073/pnas.1906623116.

    PMID: 31611378
  10. 10

    Non-PCOS Hyperandrogenic Disorders in Adolescents.

    Esquivel-Zuniga MR, Kirschner CK, McCartney CR, Burt Solorzano CM

    Seminars in reproductive medicine 2022; (40(1-02)):42-52 doi:10.1055/s-0041-1742259.

    PMID: 35052005
  11. 11

    Non-classical congenital adrenal hyperplasia: current insights into clinical implications, diagnosis and treatment.

    Loli P, Menotti S, di Filippo L, Giustina A

    Endocrine 2025; (90(1)):1-16 doi:10.1007/s12020-025-04341-5.

    PMID: 40699527
  12. 12

    Nonclassic Congenital Adrenal Hyperplasia: What Do Endocrinologists Need to Know?

    Jha S, Turcu AF

    Endocrinology and metabolism clinics of North America 2021; (50(1)):151-165 doi:10.1016/j.ecl.2020.10.008.

    PMID: 33518183
  13. 13

    Cortisol and Aldosterone Responses to Hypoglycemia and Na Depletion in Women With Non-Classic 21-Hydroxylase Deficiency.

    Kamenický P, Blanchard A, Lamaziere A, et al.

    The Journal of clinical endocrinology and metabolism 2020; (105(1)) doi:10.1210/clinem/dgz005.

    PMID: 31529070
  14. 14

    Long-read sequencing analysis of non-classical congenital adrenal hyperplasia prevalence and carrier frequency in Chinese polycystic ovarian syndrome patients.

    Huang Y, Jiang H, Zhu X, et al.

    Journal of ovarian research 2025; (18(1)):252 doi:10.1186/s13048-025-01824-x.

    PMID: 41219732
  15. 15

    Comparison of long-read sequencing and MLPA combined with long-PCR sequencing of CYP21A2 mutations in patients with 21-OHD.

    Lan T, Wang J, Chen K, et al.

    Frontiers in genetics 2024; (15()):1472516 doi:10.3389/fgene.2024.1472516.

    PMID: 39553475
  16. 16

    Genotype/phenotype correlations in 538 congenital adrenal hyperplasia patients from Germany and Austria: discordances in milder genotypes and in screened versus prescreening patients.

    Riedl S, Röhl FW, Bonfig W, et al.

    Endocrine connections 2019; (8(2)):86-94.

    PMID: 30620712
  17. 17

    CYP21A2 Gene Pathogenic Variants: A Multicenter Study on Genotype-Phenotype Correlation from a Portuguese Pediatric Cohort.

    Santos-Silva R, Cardoso R, Lopes L, et al.

    Hormone research in paediatrics 2019; (91(1)):33-45 doi:10.1159/000497485.

    PMID: 30889569
  18. 18

    CONGENITAL ADRENAL HYPERPLASIA WITH COMPOUND HETEROZYGOUS I2 SPLICE AND P453S MUTATIONS.

    Almacan B, Ozdemir N, Onay H, Hekimsoy Z

    Acta endocrinologica (Bucharest, Romania : 2005) 2022; (18(2)):228-231 doi:10.4183/aeb.2022.228.

    PMID: 36212252
  19. 19

    Issues with the Detection of Large Genomic Rearrangements in Molecular Diagnosis of 21-Hydroxylase Deficiency.

    Concolino P

    Molecular diagnosis & therapy 2019; (23(5)):563-567 doi:10.1007/s40291-019-00415-z.

    PMID: 31317337
  20. 20

    Molecular Diagnosis of Steroid 21-Hydroxylase Deficiency: A Practical Approach.

    Arriba M, Ezquieta B

    Frontiers in endocrinology 2022; (13()):834549 doi:10.3389/fendo.2022.834549.

    PMID: 35422767

This page explains the different types of Congenital Adrenal Hyperplasia for educational purposes only. Always consult your endocrinologist or medical geneticist for specific advice regarding your diagnosis and treatment plan.

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