A 7–year–old child presents to the paediatric clinic with ambiguous genitalia increasing with age. On examination, her height, weight and blood pressure were recorded within normal limits. Labia appeared bifid with 2 separate perineal openings, phallic length was 2.5 cm and no palpable gonads were noted in the inguinal region. USG shows the presence of Mullerian structures. The most probable diagnosis is –
Among the given options only 21 hydroxylase is the common cause of ambiguous genitalia.
Now the confusion arises, because 21-hydroxylase deficiency typically presents with salt wasting and hypotension, whereas the child in question is having normal BP.
Actually, some forms (simple virilizing form) of 21-hydroxylase deficiency have normal BP and no salt loss.

Type of 21-hydroxylase deficiency
(A) Classic salt wasting form

This is a severe form of deficiency characterized by features of both glucocorticoid (cortisol)/mineralocorticoid deficiency (salt wasting) and androgen excess. (Ambiguous genitalia in females). Males may be normal at birth.
This form typically manifests early, between 7-21 days of life and is a potentially life threatening condition.

(B) Classic simple virilizing form

Patients with classic simple virilizing form have impaired cortisol biosynthesis but do not develop salt loss.
Clinical features are caused solely by overproduction of androgens.
The only manifestation is ambiguous genitalia in a female child with varying degrees of clitoral enlargement and labial fusion.
Depending on the severity of clitoral enlargement and labial fusion, the diagnosis may be established at birth. However such patients may present in early childhood.

(C) Non-classic (acquired/late) from

Patients with non-classical form or late-onset form produce a normal amount of cortisol and/or aldosterone but at the expense of producing excess androgens.
These usually present in childhood or early adulthood with premature pubarche & symptoms/signs of PCOD. Hirsutism, Acne and Oligomenorrhea are the most common presenting features.
Classic Salt–Wasting 21 Hydroxylase deficiency
Simple virilizing congenital adrenal hyperplasia
Complete Androgen Insensitivity Syndrome
5–Alpha Reductase Deficiency