Can You Have PCD With Normal Biopsy and nNO Tests?

Yes, your child can still have Primary Ciliary Dyskinesia (PCD) even if their ciliary biopsy and nasal nitric oxide (nNO) tests come back completely normal ^[1][2]. Receiving normal test results when your child has obvious, severe symptoms is one of the most frustrating and confusing parts of the PCD diagnostic journey. However, certain genetic mutations cause the cilia to look completely normal and maintain normal nitric oxide levels, despite beating abnormally and causing severe disease ^[3][4].

Why Does the Biopsy Look Normal?

A traditional ciliary biopsy uses a tool called Transmission Electron Microscopy (TEM) to look at the physical structure of the cilia. TEM is excellent for spotting missing or broken parts of the cilia, but it only detects structural defects in about 70-85% of cases ^[1][5].

Some genetic mutations cause the cilia to be built with all their parts, meaning they look perfectly normal under a microscope, but they do not function correctly. The most classic example is the DNAH11 gene mutation ^[3][6]. In DNAH11-related PCD, the physical structure is intact, so the TEM biopsy appears completely normal ^[7]. However, the cilia might beat in a stiff, hyperkinetic (overactive) pattern with a reduced ability to bend ^[7][6]. Other genes, such as RSPH1, GAS8, and CCDC65, can also result in normal or near-normal structural biopsies despite causing PCD ^[1][8].

Why Are Nasal Nitric Oxide (nNO) Levels Normal?

Nasal nitric oxide (nNO) testing measures the gas produced in the nasal passages. Most people with PCD have very low nNO levels, making it a reliable first-line screening test for many ^[9].

However, patients with specific mutations like DNAH11 or RSPH1 may maintain normal or borderline normal levels of nitric oxide in their sinuses despite having PCD ^[4][2]. This can cause the screening test to incorrectly suggest the patient does not have the disease. Additionally, reliable nNO testing requires specific breathing cooperation; children under 5 or 6 years old often cannot perform the maneuver correctly, which can lead to unreliable or inconclusive results ^[9].

Getting Answers: Advanced Testing at Specialized Centers

When a child’s clinical symptoms strongly point to PCD (such as chronic wet cough, recurrent sinus infections, or organs positioned on the wrong side of the body) but the standard biopsy and nNO tests are normal, doctors rely on other tools. Because these tests are complex, it is highly recommended to seek evaluation at an accredited PCD Clinical Center.

• High-Speed Video Microscopy Analysis (HSVMA): Instead of just looking at still images of the cilia’s structure, HSVMA records live cilia under a microscope ^[6]. This allows specialized doctors to watch exactly how the cilia beat and identify the stiff or hyperkinetic movements characteristic of DNAH11 and similar mutations ^[3][6].
• Genetic Testing: Genetic testing is a powerful confirmatory tool that looks directly at the patient’s DNA for the specific spelling mistakes (mutations) causing the disease, bypassing the physical appearance of the cilia entirely ^[10][3].

What if genetic testing is also negative?
While genetic testing is highly specific, it cannot identify every single case of PCD—about 25-40% of cases remain genetically unexplained ^[11]. If genetic testing comes back normal or inconclusive, you are not at a dead end. Specialists can still diagnose and treat your child for PCD based on strong clinical symptoms combined with abnormal HSVMA results ^[12][13].

A “normal” standard biopsy and nNO test in a symptomatic child should not be the end of the evaluation. Pursuing advanced testing with a PCD specialist is a crucial next step to ensure your child receives the right care.