Differential Diagnosis for Ambiguous Genitalia in a Neonate
- Single Most Likely Diagnosis
- Congenital Adrenal Hyperplasia (CAH): This condition is the most common cause of ambiguous genitalia in neonates. The enlarged clitoris and single perineal opening are consistent with CAH, which is caused by a deficiency in enzymes involved in cortisol production, leading to an overproduction of androgens.
- Other Likely Diagnoses
- Androgen Insensitivity Syndrome (AIS): Although less likely than CAH, AIS can cause ambiguous genitalia. However, the presence of an enlarged clitoris suggests that some androgen effect is present, making complete AIS less likely.
- Ovotesticular Disorder of Sex Development (OT-DSD): This condition involves the presence of both ovarian and testicular tissue, which can lead to ambiguous genitalia. The absence of palpable masses in the labioscrotal pouches or inguinal canal does not rule out this diagnosis.
- Do Not Miss Diagnoses
- Congenital Gonadal Dysgenesis with Y Chromosome Material: This condition can increase the risk of gonadal tumors, such as gonadoblastoma. Although less common, it is crucial to identify any Y chromosome material due to the potential for malignancy.
- Denys-Drash Syndrome: A rare condition characterized by genital anomalies, nephropathy, and increased risk of Wilms tumor. Early diagnosis is critical due to the high risk of malignancy.
- Rare Diagnoses
- Mosaicism or Chimerism: These conditions involve the presence of two or more cell lines with different genetic makeup, which can lead to ambiguous genitalia. However, they are rare and typically require specific genetic testing for diagnosis.
- Leydig Cell Tumors: Although rare in neonates, these tumors can produce androgens, leading to virilization of a female fetus. The absence of a palpable mass does not entirely rule out this diagnosis, but it makes it less likely.