There are certain ICD-10 codes that are age-specific and will trigger a denial based on age/ICD-10 combo.
Copied and pasted here, so pardon the formatting...
Diagnosis Description
A4851 Infant botulism
B0820 Exanthema subitum [sixth disease], unspecified
B0821 Exanthema subitum [sixth disease] due to human herpesvirus 6
B0822 Exanthema subitum [sixth disease] due to human herpesvirus 7
C9330 Juvenile myelomonocytic leukemia, not achieve remission
C9331 Juvenile myelomonocytic leukemia, in remission
C9332 Juvenile myelomonocytic leukemia, in relapse
E301 Precocious puberty
E308 Other disorders of puberty
F642 Gender identity disorder of childhood
F843 Other childhood disintegrative disorder
G937 Reye's syndrome
H26001 Unspecified infantile and juvenile cataract, right eye
H26002 Unspecified infantile and juvenile cataract, left eye
H26003 Unspecified infantile and juvenile cataract, bilateral
H26009 Unspecified infantile and juvenile cataract, unspecified eye
H26011 Infantile and juv cortical/lamellar/zonular cataract, r eye
H26012 Infantile and juv cortical/lamellar/zonular cataract, l eye
H26013 Infantile and juv cortical/lamellar/zonular cataract, bi
H26019 Infantile & juv cortical/lamellar/zonular cataract, unsp eye
H26031 Infantile and juvenile nuclear cataract, right eye
H26032 Infantile and juvenile nuclear cataract, left eye
H26033 Infantile and juvenile nuclear cataract, bilateral
H26039 Infantile and juvenile nuclear cataract, unspecified eye
H26041 Ant subcapsular polar infantile and juvenile cataract, r eye
H26042 Ant subcapsular polar infantile and juv cataract, left eye
H26043 Ant subcapsular polar infantile and juvenile cataract, bi
H26049 Ant subcapsular polar infantile and juv cataract, unsp eye
H26051 Post subcapsular polar infantile and juv cataract, r eye
H26052 Post subcapsular polar infantile and juv cataract, left eye
H26053 Post subcapsular polar infantile and juvenile cataract, bi
H26059 Post subcapsular polar infantile and juv cataract, unsp eye
H26061 Combined forms of infantile and juvenile cataract, right eye
H26062 Combined forms of infantile and juvenile cataract, left eye
H26063 Combined forms of infantile and juvenile cataract, bilateral
H26069 Combined forms of infantile and juvenile cataract, unsp eye
H2609 Other infantile and juvenile cataract
L122 Chronic bullous disease of childhood
L2083 Infantile (acute) (chronic) eczema
L210 Seborrhea capitis
L211 Seborrheic infantile dermatitis
L444 Infantile papular acrodermatitis [Gianotti-Crosti]
L704 Infantile acne
N922 Excessive menstruation at puberty
R0481 Acute idiopathic pulmonary hemorrhage in infants
R1083 Colic
R620 Delayed milestone in childhood
R6251 Failure to thrive (child)
R6811 Excessive crying of infant (baby)
R6812 Fussy infant (baby)
R6813 Apparent life threatening event in infant (ALTE)
R6819 Other nonspecific symptoms peculiar to infancy
T7402XA Child neglect or abandonment, confirmed, initial encounter
T7402XD Child neglect or abandonment, confirmed, subs encntr
T7402XS Child neglect or abandonment, confirmed, sequela
T7412XA Child physical abuse, confirmed, initial encounter
T7412XD Child physical abuse, confirmed, subsequent encounter
T7412XS Child physical abuse, confirmed, sequela
T7422XA Child sexual abuse, confirmed, initial encounter
T7422XD Child sexual abuse, confirmed, subsequent encounter
T7422XS Child sexual abuse, confirmed, sequela
T7432XA Child psychological abuse, confirmed, initial encounter
T7432XD Child psychological abuse, confirmed, subsequent encounter
T7432XS Child psychological abuse, confirmed, sequela
T744XXA Shaken infant syndrome, initial encounter
T744XXD Shaken infant syndrome, subsequent encounter
T744XXS Shaken infant syndrome, sequela
T7492XA Unspecified child maltreatment, confirmed, initial encounter
T7492XD Unspecified child maltreatment, confirmed, subs encntr
T7492XS Unspecified child maltreatment, confirmed, sequela
T7602XA Child neglect or abandonment, suspected, initial encounter
T7602XD Child neglect or abandonment, suspected, subs encntr
T7602XS Child neglect or abandonment, suspected, sequela
T7612XA Child physical abuse, suspected, initial encounter
T7612XD Child physical abuse, suspected, subsequent encounter
T7612XS Child physical abuse, suspected, sequela
T7622XA Child sexual abuse, suspected, initial encounter
T7622XD Child sexual abuse, suspected, subsequent encounter
T7622XS Child sexual abuse, suspected, sequela
T7632XA Child psychological abuse, suspected, initial encounter
T7632XD Child psychological abuse, suspected, subsequent encounter
T7632XS Child psychological abuse, suspected, sequela
T7692XA Unspecified child maltreatment, suspected, initial encounter
T7692XD Unspecified child maltreatment, suspected, subs encntr
T7692XS Unspecified child maltreatment, suspected, sequela
Z00121 Encounter for routine child health exam w abnormal findings
Z00129 Encntr for routine child health exam w/o abnormal findings
Z002 Encounter for exam for period of rapid growth in childhood
Z003 Encounter for examination for adolescent development state
Z0070 Encntr for exam for delay growth in chldhd w/o abn findings
Z0071 Encntr for exam for delay growth in chldhd w abn findings
Z0442 Encounter for exam and obs following alleged child rape
Z0472 Encntr for exam and obs fol alleged child physical abuse
Z134 Encntr screen for certain developmental disorders in chldhd
Z6221 Child in welfare custody
Z623 Hostility towards and scapegoating of child
Z69010 Encntr for mental hlth serv for victim of prntl child abuse
Z69020 Encntr for mntl hlth serv for vctm of non-prntl child abuse
Z72810 Child and adolescent antisocial behavior
Z73810 Behavioral insomnia of childhood, sleep-onset assoc type
Z73811 Behavioral insomnia of childhood, limit setting type
Z73812 Behavioral insomnia of childhood, combined type
Z73819 Behavioral insomnia of childhood, unspecified type
Z762 Encntr for hlth suprvsn and care of healthy infant and child